What does the research show about total testosterone?

Total testosterone

Total testosterone is the first test for low testosterone in men. Lower limits differ by source, from 264 to 350 ng/dL, and results run lower in the afternoon and after eating. Low levels go with more deaths and diabetes in men. In trials, testosterone treatment improved sexual function, did not change heart attacks or strokes, and raised fractures.

Checked 2026-11-13

Status: A blood test ordered by a clinician and also sold direct to consumers by some US laboratories. FDA classifies testosterone test systems as class I devices [1]. Since 2010 the Centers for Disease Control and Prevention has run an accuracy-based standardization program for testosterone assays, and the Endocrine Society reported in 2018 that most immunoassay kit makers and local hospital laboratories had not been certified [2].
Measures: All the testosterone in blood, both the part bound to protein and the roughly 2% that is free [3].
Also called: testosterone, total testosterone, testosterone total, serum testosterone, testosterone serum, total T, TT, testosterone LC/MS, testosterone LC-MS/MS, testosterone by mass spectrometry, testosterone immunoassay
Tested for: low testosterone, low sex drive, erectile dysfunction, fatigue, muscle loss, infertility, polycystic ovary syndrome, excess hair growth in women, monitoring testosterone therapy

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Linked in research4

StrongLinked to more deaths in men at low testosterone: below 213 ng/dL for death from any cause and below 153 ng/dL for cardiovascular death in pooled cohorts.
ModerateShown in genetic and cohort studies to run in opposite directions by sex: higher testosterone went with less type 2 diabetes in men and more in women.
LimitedOne trial found more fractures, not fewer, when testosterone was raised in men with low levels: 3.5% against 2.5% on placebo over 3 years.
LimitedOne genetic study found each standard deviation of genetically higher testosterone raised the odds of polycystic ovary syndrome in women by about half.

Reported risks0

No risks sourced yet.

Reference ranges

Each range is the one its source published, in ng/dL. Also reported in nmol/L. Where sources differ, each is shown.

Endocrine Society guideline, 2018, with the harmonized range of Travison and colleagues, 2017

Men, for assays certified by the Centers for Disease Control and Prevention · [2], [4]

Range	What the source calls it
below 264 ng/dL	No name given
264 to 916 ng/dL	"harmonized reference range"
above 916 ng/dL	No name given

The 2.5th and 97.5th percentiles in men aged 19 to 39 whom the study classed as healthy and nonobese, drawn from four cohorts in the United States and Europe with 9,054 men in all, after each cohort's assay was cross-calibrated to a reference method at the Centers for Disease Control and Prevention. The 5th and 95th percentiles were 303 and 852 ng/dL [4]. The guideline says clinicians can use this range for all certified assays and that ranges from laboratories that are not certified may vary considerably. It prints the lower limit as 264 ng/dL (9.2 nmol/L). It makes a diagnosis of hypogonadism only in men with symptoms and signs and with unequivocally and consistently low levels, measured fasting on two separate mornings [2].

American Urological Association guideline, 2018

Men, on two early morning measurements · [3]

Range	What the source calls it
below 300 ng/dL	"low testosterone"
300 or above ng/dL	No name given

The guideline calls 300 ng/dL a reasonable cut-off in support of the diagnosis of low testosterone, on two total testosterone measurements taken on separate occasions in the early morning. It states that a level below 300 ng/dL alone does not define testosterone deficiency, which also requires symptoms or signs. The panel supported the figure with testosterone treatment trials whose median baseline level was 249 ng/dL, and notes that other societies have used thresholds from 230 to 350 ng/dL [3].

European Association of Urology guideline, 2026

Men with signs and symptoms of androgen deficiency, fasting morning sample · [5]

Range	What the source calls it
below 350 ng/dL	No name given
350 or above ng/dL	No name given

Printed as 12 nmol/L (3.5 ng/mL), which the guideline calls a reliable threshold to diagnose late-onset hypogonadism. It bases that diagnosis on specific signs and symptoms together with consistently low levels, measured fasting between 07:00 and 10:00 and repeated on at least two occasions. It describes levels below 8 nmol/L as more severe hypogonadism and below 6 nmol/L (1.75 ng/mL) as severe [5]. The British Society for Sexual Medicine uses the same 12 nmol/L figure and describes 8 to 12 nmol/L as close to the lower normal range [6].

International Society of Andrology, ISSAM, EAU, EAA and ASA recommendations, 2008

Men assessed for late-onset hypogonadism, morning sample · [7]

Range	What the source calls it
below 230 ng/dL	No name given
230 to 350 ng/dL	No name given
above 350 ng/dL	No name given

The five societies state that there are no generally accepted lower limits of normal. They print two cut points, 8 nmol/L (230 ng/dL) and 12 nmol/L (350 ng/dL). Between the two they suggest repeating the measurement with sex hormone-binding globulin to calculate free testosterone, or measuring free testosterone by equilibrium dialysis. They describe general agreement that a level above 350 ng/dL does not require testosterone substitution, and base the lower cut point on data from younger men. The sample is to be taken between 07:00 and 11:00 [7].

European Male Aging Study criteria, 2010

Men aged 40 to 79 who have at least three sexual symptoms · [8]

Range	What the source calls it
below 320 ng/dL	No name given
320 or above ng/dL	No name given

The cohort's criteria for late-onset hypogonadism are at least three sexual symptoms together with total testosterone below 11 nmol/L (3.2 ng/mL) and free testosterone below 220 pmol/L (64 pg/mL). They were derived from 3,369 men at eight European centers, with morning samples measured by mass spectrometry. The chance of the three sexual symptoms and of limited physical vigor rose as total testosterone fell through 8.0 to 13.0 nmol/L (2.3 to 3.7 ng/mL) [8].

Framingham Heart Study reference sample, 2011

Men, from a reference sample aged 19 to 40 · [9]

Range	What the source calls it
below 348.3 ng/dL	"low"
348.3 or above ng/dL	"normal"

The 2.5th percentile in 456 men aged 19 to 40 whom the study classed as healthy and nonobese, measured by liquid chromatography tandem mass spectrometry. The mean was 723.8 ng/dL. The abstract prints no upper limit. This sample was later one of the four cohorts cross-calibrated to give the harmonized lower limit of 264 ng/dL [9][4].

US National Library of Medicine, MedlinePlus, men aged 17 to 50

Males aged 17 to 50 · [10]

Range	What the source calls it
below 249 ng/dL	No name given
249 to 836 ng/dL	"normal"
above 836 ng/dL	No name given

Printed as 249 to 836 ng/dL (8.6 to 29.0 nmol/L). MedlinePlus states that ranges vary slightly among laboratories and gives 7 a.m. to 10 a.m. as the time for the blood sample. It names no assay [10].

US National Library of Medicine, MedlinePlus, men over 50

Males over 50 · [10]

Range	What the source calls it
below 193 ng/dL	No name given
193 to 740 ng/dL	"normal"
above 740 ng/dL	No name given

Printed as 193 to 740 ng/dL (6.7 to 25.7 nmol/L). It names no assay [10].

American Board of Internal Medicine laboratory reference ranges, 2026, men

Men, as a general laboratory reference range · [11]

Range	What the source calls it
below 291 ng/dL	No name given
291 to 1100 ng/dL	"reference range"
above 1100 ng/dL	No name given

The table names no assay, age group or time of day [11].

NHANES analysis by age, Zhu and colleagues, 2022, men aged 20 to 24

Men aged 20 to 24, morning sample · [12]

Range	What the source calls it
below 409 ng/dL	"low"
409 or above ng/dL	No name given

The authors took the middle third of morning results in each age group as the normal level, following a definition from the American Urological Association, and set the cutoff for low testosterone at its lower edge. For this age group the middle third was 409 to 558 ng/dL. Based on 1,486 men aged 20 to 44 in the 2011 to 2016 National Health and Nutrition Examination Surveys. A lower third of results sits below each cutoff by construction, so these are not percentile-based reference limits of the usual kind [12].

NHANES analysis by age, Zhu and colleagues, 2022, men aged 25 to 29

Men aged 25 to 29, morning sample · [12]

Range	What the source calls it
below 413 ng/dL	"low"
413 or above ng/dL	No name given

The lower edge of the middle third of results for this age group, which was 413 to 575 ng/dL. See the block for ages 20 to 24 for how the cutoffs were set [12].

NHANES analysis by age, Zhu and colleagues, 2022, men aged 30 to 34

Men aged 30 to 34, morning sample · [12]

Range	What the source calls it
below 359 ng/dL	"low"
359 or above ng/dL	No name given

The lower edge of the middle third of results for this age group, which was 359 to 498 ng/dL. See the block for ages 20 to 24 for how the cutoffs were set [12].

NHANES analysis by age, Zhu and colleagues, 2022, men aged 35 to 39

Men aged 35 to 39, morning sample · [12]

Range	What the source calls it
below 352 ng/dL	"low"
352 or above ng/dL	No name given

The lower edge of the middle third of results for this age group, which was 352 to 478 ng/dL. See the block for ages 20 to 24 for how the cutoffs were set [12].

NHANES analysis by age, Zhu and colleagues, 2022, men aged 40 to 44

Men aged 40 to 44, morning sample · [12]

Range	What the source calls it
below 350 ng/dL	"low"
350 or above ng/dL	No name given

The lower edge of the middle third of results for this age group, which was 350 to 473 ng/dL. See the block for ages 20 to 24 for how the cutoffs were set [12].

US National Library of Medicine, MedlinePlus, women aged 17 to 50

Females aged 17 to 50 · [10]

Range	What the source calls it
below 8.4 ng/dL	No name given
8.4 to 48.1 ng/dL	"normal"
above 48.1 ng/dL	No name given

Printed as 8.4 to 48.1 ng/dL (0.3 to 1.7 nmol/L). It names no assay [10]. Immunoassays are least accurate at the low levels found in women: in one comparison, 7 of 10 read higher than mass spectrometry in women's samples, by 46% on average [13].

US National Library of Medicine, MedlinePlus, women over 50

Females over 50 · [10]

Range	What the source calls it
below 2.9 ng/dL	No name given
2.9 to 40.1 ng/dL	"normal"
above 40.1 ng/dL	No name given

Printed as 2.9 to 40.1 ng/dL (0.1 to 1.4 nmol/L). It names no assay [10].

American Board of Internal Medicine laboratory reference ranges, 2026, women

Women, as a general laboratory reference range · [11]

Range	What the source calls it
below 18 ng/dL	No name given
18 to 54 ng/dL	"reference range"
above 54 ng/dL	No name given

The table names no assay, age group or menopausal status [11].

Braunstein and colleagues, 2011, premenopausal women

Premenopausal women with regular menstrual cycles, estimated for age 30 · [14]

Range	What the source calls it
below 15 ng/dL	No name given
15 to 46 ng/dL	"reference range"
above 46 ng/dL	No name given

The estimated 5th and 95th percentiles for a 30-year-old woman, from 161 women aged 18 to 49 sampled in the morning at three points in the menstrual cycle. Levels declined with age. The authors report that the mid-cycle rise is small against overall variability, so the range applies on any cycle day. The authors included employees of a commercial laboratory and of two companies [14]. A German cohort of 985 women aged 20 to 80, measured by mass spectrometry, reported a reference range of 0.35 to 1.97 nmol/L over the whole age span [15].

What has been shown to move it

Shown to lower it7

Hormonal birth controlModerateStudied in womenHow often is not known

Lower testosterone and higher SHBG

Shown to lower total testosterone and cut free testosterone by about 61% in healthy women on combined pills, while SHBG rose about 99 nmol/L.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: Total testosterone fell (MD -0.49 nmol/L, 95% CI -0.55 to -0.42), free testosterone fell 61% (relative level 0.39), and SHBG rose (MD 99.08 nmol/L, 95% CI 86.43 to 111.73). Ethinyl estradiol dose and progestin type did not change the testosterone fall, but pills with second-generation progestins or 20 to 25 µg ethinyl estradiol raised SHBG less [7].
Population: 1,495 healthy women aged 18 to 40 in 42 studies [7].
Sources: [7]
Caveats: Half the studies were non-comparative. The clinical effects of lower androgens remain unclear [7].

InositolModerateStudied in women

Hormones and blood sugar in PCOS

Shown to lower free and total testosterone and glucose and raise SHBG in women with PCOS. Metformin did better on hirsutism.

The numbers and sources

Effect: Against placebo, inositol lowered BMI (MD -0.45), free testosterone (MD -0.41), total testosterone (MD -20.4) and glucose (MD -3.14), and raised sex-hormone-binding globulin (MD 32.1) [1]. The guideline review found benefits for some metabolic measures and none for others. Metformin did better on waist-hip ratio and hirsutism [3].
Population: 1,691 women in 26 trials [1]; 2,230 women in 30 trials [3].
Sources: [1], [3]
Caveats: Units are as reported in the abstract. The guideline review rated BMI evidence very uncertain [3].

Keto dietModerateStudied in women

Reproductive hormones and cycles in PCOS

Shown in pooled studies, mostly before and after the diet, to lower LH and testosterone and raise SHBG in women with PCOS. Against other diets, androgen results were inconsistent.

Compared with before the diet, in the same women [25][23][21][22]; other diets [21]; low-calorie diets [22]

The numbers and sources

Effect: After 45 days or more on a ketogenic diet, the LH to FSH ratio fell (d -0.851, 95% CI -1.015 to -0.686), free testosterone fell (d -0.223, 95% CI -0.328 to -0.119) and SHBG rose (d 9.086, 95% CI 3.379 to 14.792) [25]. A second review found lower LH, LH to FSH ratio, free and total testosterone and higher SHBG and FSH after the diet [23]. Menstrual cycle length shortened and LH fell from before to after the diet, while androgen results against other diets were inconsistent [21]. In 2 RCTs, LH was lower than on low-calorie diets [22].
Population: Women with PCOS in single- or double-arm clinical trials [25]; 7 studies [23]; 15 studies, 10 pooled [21]; 10 studies including 3 RCTs [22].
Sources: [25], [23], [21], [22]
Caveats: Diets lasted weeks to months, and all reviews were limited by small, mostly uncontrolled studies. Pregnancy and live birth data were too scarce to pool [23].

Low-carb dietModerateStudied in women

Testosterone and SHBG in PCOS

In one meta-analysis, testosterone fell and SHBG rose more than on a regular diet only in trials of women with PCOS lasting longer than 4 weeks.

Compared with a regular diet with about 45% of energy from carbohydrate [13]

The numbers and sources

Effect: In trials of low-carbohydrate diets lasting more than 4 weeks, testosterone fell (SMD -1.79, 95% CI -3.22 to -0.36), SHBG rose (MD 5.98, 95% CI 3.51 to 8.46) and FSH rose (MD 0.39) more than on a regular diet. Diets low in both fat and carbohydrate raised SHBG and FSH more than higher-fat versions [13].
Population: 327 women with PCOS in 8 RCTs [13].
Sources: [13]
Caveats: These are subgroup results by trial length, from small trials. The abstract does not report an overall pooled effect on testosterone or SHBG [13].

SARMsGrey marketModerateHow often is not known

Lower testosterone and HDL cholesterol

Shown to lower testosterone and HDL cholesterol in healthy men, more at higher doses. Levels returned to baseline after stopping.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: LGD-4033 lowered total testosterone, sex hormone-binding globulin, HDL cholesterol and triglycerides in a dose-dependent way. FSH and free testosterone fell at the highest dose. Levels returned to baseline after stopping [1]. The 2026 review reports suppression of testosterone, sex hormone-binding globulin and HDL cholesterol across randomized trials, with reversible rises in liver enzymes for some compounds [4].
Population: 76 healthy young men over 21 days and 5 weeks of follow-up [1]; trials summarized in a review [4].
Sources: [1], [4]
Caveats: Trial doses were lower and shorter than the stacked, unmonitored use the review describes [4].

Vitamin DModerateStudied in women

Excess hair and androgens in PCOS

Not shown to change hair growth scores or SHBG in women with PCOS in one review. Total testosterone fell slightly against placebo.

Compared with placebo [73]; placebo, metformin, short-acting contraceptives, ovulation drugs or assisted reproduction without vitamin D [69]

Total testosterone fell by 0.17 (95% CI 0.05 to 0.29) and serum vitamin D rose by 17.81.

The numbers and sources

Effect: Across 13 RCTs (840 women), modified Ferriman-Gallwey hair scores (MD 0.04, 95% CI -0.79 to 0.86) and SHBG (MD 1.33, 95% CI -2.70 to 5.36) did not differ from placebo. Total testosterone fell by 0.17 (95% CI 0.05 to 0.29) and serum vitamin D rose by 17.81 [73]. A review of add-on vitamin D in women seeking pregnancy also found lower androgen levels (MD -2.31, 95% CI -3.51 to -1.11) [69].
Population: 840 women with PCOS in 13 RCTs [73]; 1,961 women with PCOS in 20 RCTs [69].
Sources: [73], [69]
Caveats: The abstract of [73] does not give units for testosterone or vitamin D. The hair score result rests on one review.

SpironolactoneLimitedStudied in women

Hirsutism and cycles in PCOS

Small open-label trials in women with PCOS found hirsutism scores fell more with spironolactone than with metformin, and more with the two combined than with either alone.

Compared with metformin 1,000 mg a day [22][23]; metformin 1,700 mg a day alone [24]; spironolactone alone [23]

In a three-arm trial, spironolactone 50 mg plus metformin raised cycles a year and lowered hirsutism score, total testosterone and glucose and insulin area under the curve more than either drug alone (P < .05).

The numbers and sources

Effect: Over 6 months, the Ferriman-Gallwey hirsutism score fell from 12.9 to 8.7 on spironolactone 50 mg a day and from 12.5 to 10.0 on metformin. Menstrual cycles rose from 6.6 to 10.2 a year on spironolactone and from 5.7 to 9.1 on metformin (P = 0.0037). Testosterone fell in both groups, and weight and blood pressure did not change [22]. In a three-arm trial, spironolactone 50 mg plus metformin raised cycles a year and lowered hirsutism score, total testosterone and glucose and insulin area under the curve more than either drug alone (P < .05) [23]. Adding spironolactone 25 mg to metformin lowered the hirsutism score more than metformin alone (P < 0.001), while regular menses returned in 68% on the combination and 82% on metformin alone [24].
Population: 82 adolescent and young women with PCOS randomized, 69 completing, mean age 22.6 [22]; 198 women with PCOS randomized, 169 completing [23]; 56 women with PCOS [24].
Sources: [22], [23], [24]
Caveats: All three trials were open-label, small and lasted 6 months, with no placebo group. Two came from the same research group [22][23]. Not an FDA-approved use [3].

Shown to raise it6

AshwagandhaStrong

Testosterone

Shown to raise testosterone in men, by about 57 ng/dL in one review, with no change in women. Rises stayed within physiological ranges.

The numbers and sources

Effect: Across 20 trials of cognitive and physical outcomes, testosterone rose (SMD 0.33, 95% CI 0.13 to 0.54, I² 20.8%) [8]. A hormone meta-analysis found testosterone rose by 57.43 ng/dL in men but not in women (5.09 ng/dL), and estradiol did not change [6]. In 57 overweight men aged 40 to 70 with mild fatigue, 8 weeks of an ashwagandha extract was associated with a 14.7% greater rise in salivary testosterone and an 18% greater rise in DHEA-S than placebo. Fatigue, vigor and sexual well-being did not differ between groups [9].
Population: 1,249 participants in 20 RCTs [8]. 1,706 adults in 23 RCTs [6]. 57 men, crossover, 43 completed all 16 weeks [9].
Sources: [8], [6], [9]
Caveats: The 57-man trial tested one branded extract and was funded by its maker, Arjuna Natural Ltd [9]. In healthy adults, testosterone rises stayed within physiological ranges [7].

DHEAModerateStudied in women

Testosterone and estradiol levels in postmenopausal women

Shown to raise testosterone by about 24 ng/dL and estradiol by about 8 pg/mL in postmenopausal women.

The numbers and sources

Effect: DHEA raised serum testosterone by 24.31 ng/dL (95% CI 15.22 to 33.40) and estradiol by 7.86 pg/mL (95% CI 6.33 to 9.40). Trials using 50 mg a day or more showed larger rises in testosterone (29.65 ng/dL) [10].
Population: Postmenopausal women in 21 RCTs [10].
Sources: [10]
Caveats: These are blood levels, not symptoms or outcomes. Subgroup confidence intervals overlapped [10].

Letrozole and clomipheneModerateStudied in men

Testosterone in men: clomiphene

Shown to raise total testosterone in men with low testosterone, by about 274 ng/dL against placebo, in pooled trials of clomiphene or enclomiphene.

Compared with placebo [13]; testosterone gel [13]; human chorionic gonadotropin [13]; the same men before treatment [14]

The numbers and sources

Effect: Against placebo, clomiphene or enclomiphene raised total testosterone by 273.76 ng/dL (95% CI 191.87 to 355.66, I² 89%), LH by 4.66 IU/L and FSH by 4.59 IU/L. Total testosterone did not differ from testosterone gel. Levels were higher than with hCG alone [13]. Across 17 studies pooled in a second review, total testosterone rose during treatment (pooled estimate 2.60, 95% CI 1.82 to 3.38, unit not given in the abstract), along with free testosterone, LH, FSH, SHBG and estradiol. Symptom scores on the Androgen Deficiency in Aging Males questionnaire improved. Side effects were reported by fewer than 10% of study populations and no serious adverse events were reported [14].
Population: Men with functional hypogonadism in randomized trials [13]. 1,642 men with hypogonadism in 19 studies, 4 randomized and 15 observational, treated for 1.5 to 52 months [14].
Sources: [13], [14]
Caveats: The first review pooled clomiphene with enclomiphene and heterogeneity was high [13]. The second rests mostly on before-and-after observational studies [14]. Use in men is off-label in the US [1]. Neither abstract reports fractures, heart events or fertility.

Tongkat aliModerateStudied in men

Total testosterone

Shown to raise total testosterone in men, including men with low testosterone, in few small trials, one run partly by the maker.

The numbers and sources

Effect: Across 5 RCTs, tongkat ali raised total testosterone (SMD 1.352, 95% CI 0.565 to 2.138), with the effect confirmed in the hypogonadism subgroup [1]. In 105 men aged 50 to 70 with testosterone below 300 ng/dL, 200 mg a day raised total testosterone over placebo at weeks 4, 8 and 12, and free testosterone did not differ between groups [2].
Population: Healthy and hypogonadal men in 9 studies reviewed and 5 pooled [1]; ageing men in India for 12 weeks [2].
Sources: [1], [2]
Caveats: Few small trials. Two authors of [2], including the first author, were at Biotropics Malaysia Berhad, maker of the Physta extract it tested.

FenugreekLimitedStudied in men

Testosterone

Limited evidence: total testosterone rose by a small amount in men, free testosterone did not change, and certainty was very low.

An earlier meta-analysis of 4 trials reported a significant effect on total testosterone without stating its size in the abstract.

The numbers and sources

Effect: Across 6 placebo-controlled trials, fenugreek preparations raised total testosterone by a small amount (SMD 0.25, 95% CI 0.02 to 0.48, I² 0%), while free testosterone did not change (SMD 0.08, 95% CI -0.48 to 0.63). None of 13 studies was rated low risk of bias, and certainty was very low. The authors state the evidence does not support testosterone-boosting claims [4]. An earlier meta-analysis of 4 trials reported a significant effect on total testosterone without stating its size in the abstract [5]. In 95 men aged 40 to 80, 12 weeks of an extract did not raise plasma testosterone over placebo (9.0%, p = 0.122) but raised salivary testosterone (37.2%, p = 0.042) [6].
Population: Adult men [4][5]; 95 men aged 40 to 80 who completed a 12-week trial [6].
Sources: [4], [5], [6]
Caveats: The trial in [6] was funded in part by Vitas Ltd and PurOmega Ltd, and its product also contained essential nutrients.

hCGLimitedStudied in men

Raising testosterone in men with low testosterone

One trial found testosterone rose from about 2.3 to 5.2 nmol/L on hCG, clomiphene or both in men with low testosterone, with no difference between groups.

The numbers and sources

Effect: Testosterone rose from a mean of 2.31 nmol/L to 5.17 nmol/L by 3 months on hCG, clomiphene or both, with no significant difference between groups. Symptom scores rose most with the combination [7].
Population: 282 men with low testosterone seeking to keep fertility, randomized to three arms for 3 months [7].
Sources: [7]
Caveats: One short trial with no placebo arm.

Studies disagree3

D-aspartic acidModerateStudied in men

Testosterone

Mixed results: one 12-day trial found testosterone up 42% from baseline in untrained men, while trials in trained men found no rise or a fall at 6 g.

The numbers and sources

Effect: In 23 men aged 27 to 37 given 3.12 g of sodium D-aspartate a day for 12 days, testosterone rose from 4.5 to 6.4 ng/mL, a 42% increase over baseline, and LH rose 33%. Twenty men on placebo did not change [1]. In resistance-trained men, 3 g a day for 28 days did not change total or free testosterone, LH or estradiol [2]. In 24 trained men over 14 days, 3 g a day had no effect, and 6 g a day lowered total and free testosterone [3]. In 22 trained men over 12 weeks, 6 g a day did not change total or free testosterone [4]. In 16 boxers at simulated altitude, 6 g a day for 14 days did not change resting testosterone or LH [5]. A systematic review of 4 human studies found the results inconsistent and the studies few and of poor quality [6].
Population: Healthy men in Italy [1]; resistance-trained men [2][3][4]; male boxers [5].
Sources: [1], [2], [3], [4], [5], [6]
Caveats: The rise in [1] was reported against the same men's baseline, and the product was a commercial preparation also containing vitamins B6, B12 and folic acid. All trials were small and lasted 2 to 12 weeks.

MetforminModerateStudied in women

Excess hair and androgens in PCOS

Mixed results: against the pill, hair growth improved about the same in one review and less in overweight women in another. Metformin lowered testosterone against placebo.

Compared with combined oral contraceptive pills [35][36]; metformin combined with the pill [36]; placebo [31]; lifestyle change with or without placebo [33]

The numbers and sources

Effect: Hirsutism did not differ between metformin and combined oral contraceptive pills, while free androgen index was 7.08 higher, SHBG 118.61 nmol/L lower and testosterone 0.48 nmol/L higher on metformin than on the pill [35]. In a Cochrane review, metformin may improve hirsutism less than the pill in women with BMI 25 to 30 (MD 1.92, 95% CI 1.21 to 2.64, 5 RCTs, 254 women), with an uncertain difference at other BMIs. Metformin alone and the pill alone each improved hirsutism less than the two combined [36]. Against placebo, metformin lowered total testosterone (SMD -0.33, 95% CI -0.49 to -0.17) [31]. Lifestyle change plus metformin did not differ from lifestyle change on clinical or biochemical hyperandrogenism, while metformin alone gave lower testosterone than lifestyle change [33].
Population: 36 RCTs in women with PCOS [35]; 44 RCTs with 2,253 women and adolescents with PCOS [36]; 24 RCTs with 564 women given metformin [31]; 12 RCTs with 608 women [33].
Sources: [35], [36], [31], [33]
Caveats: Cochrane evidence quality was very low to low [36]. Hirsutism scales and trial lengths varied.

D-aspartic acidLimitedStudied in menHow often is not known

Lower testosterone at 6 g a day

One small trial found 6 g a day for 14 days lowered total and free testosterone in 24 trained men. A 12-week trial found no change.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In trained men, 6 g a day for 14 days lowered total testosterone (p = 0.03), and free testosterone was lower than with the flour placebo (p = 0.005). Estradiol, SHBG and albumin did not change [3].
Population: 24 resistance-trained men [3].
Sources: [3]
Caveats: The 12-week trial at the same dose found no change in testosterone [4].

Tested, and not shown to change it6

Soy foodsStrongStudied in men

Testosterone and estrogen in men

Not shown to change total or free testosterone, estrogen or SHBG in men eating soy foods, soy protein or isoflavones, in two pooled analyses of clinical studies.

Compared with placebo groups [15]; values before intake in the same men, in simpler models [15]; control and baseline values the abstract does not detail [14]

The numbers and sources

Effect: Across 41 studies, soy protein or isoflavone intake had no significant effect on total testosterone, free testosterone, estradiol, estrone or SHBG, regardless of the statistical model, dose or study duration [14]. An earlier analysis of 15 placebo-controlled treatment groups, and 36 groups in simpler models, found no effect on testosterone, SHBG, free testosterone or free androgen index [15].
Population: Total testosterone measured in 1,753 men, free testosterone in 752 and estradiol in 1,000 [14]. Adult men in 32 reports [15].
Sources: [14], [15]
Caveats: Several authors of both analyses overlap. Studies included isoflavone extracts from soy or red clover as well as soy foods [14][15].

TribulusStrongStudied in men

Testosterone

Not shown to raise testosterone in men when taken alone. Rises appeared only in combined supplements or in a few studies of men with hypogonadism.

The numbers and sources

Effect: A systematic review of 11 studies found that testosterone rose in humans only when tribulus was part of a combined supplement, and that trials varied too much to pool [1]. In 21 men aged 20 to 36, 10 or 20 mg/kg a day for 4 weeks did not change testosterone, androstenedione or LH compared with placebo [2]. In 30 men with erectile dysfunction, 800 mg a day for 30 days did not change total testosterone (417 to 409 ng/dL, against 443 to 466 ng/dL with placebo) [3]. A review of 7 studies in physically active men found no clear effect on hormones [4]. In 30 CrossFit-trained men, testosterone fell 21.9% with placebo and was unchanged (-0.2%) with 770 mg a day over 6 weeks [5]. A 2026 meta-analysis of 8 RCTs in men with erectile dysfunction found total testosterone did not differ from placebo [6]. A 2025 systematic review of 10 studies (483 men) found that 8 reported no significant change in androgens. The 2 that found rises, of 60 to 70 ng/dL within groups, were in men with hypogonadism [7].
Population: Healthy and athletic men in RCTs [1][4]; young men in Bulgaria [2]; men with erectile dysfunction in Brazil [3]; CrossFit athletes in Spain [5]; men with erectile dysfunction in RCTs [6]; men aged 16 to 70, healthy or with infertility, erectile dysfunction or hypogonadism [7].
Sources: [1], [2], [3], [4], [5], [6], [7]
Caveats: Small trials of 21 to 30 men. The CrossFit trial was single-blind [5].

Vitamin DModerateStudied in men

Testosterone in men

Not shown to change testosterone in adult men.

The numbers and sources

Effect: Across 11 trial comparisons, vitamin D did not change total testosterone (MD 0.47 nmol/L, 95% CI -0.50 to 1.44, I² 24.1%), SHBG (MD 0.27 nmol/L, 95% CI -2.14 to 2.68) or free androgen index (MD -0.37, 95% CI -4.28 to 3.55) [32].
Population: Adult men in RCTs [32].
Sources: [32]
Caveats: GRADE certainty was low for total testosterone, SHBG and free androgen index, and very low for calculated free testosterone [32].

DIMLimitedStudied in men

Hormonal acne and testosterone in men

One small trial found DIM did not significantly change testosterone in 45 men with prostate cancer. Acne has been tested only in the lab, against acne bacteria.

The numbers and sources

Effect: In 45 men awaiting prostate surgery, 21 to 28 days of DIM or placebo produced no significant change in plasma testosterone, PSA or IGF-1 measures. Only the urinary 2-hydroxyestrone to 16-hydroxyestrone ratio changed, at the higher dose [3]. In male rats given DIM for 53 days, one middle dose had an anti-androgenic effect, and higher doses lowered sperm motility and damaged testicular tissue [7]. In the lab, DIM inhibited growth and biofilm formation by Cutibacterium acnes, the main acne bacterium [8].
Population: 45 men with prostate cancer [3]. 38 Sprague Dawley rats [7]. Bacterial cultures [8].
Sources: [3], [7], [8]
Caveats: The human trial was short, in men with prostate cancer, and testosterone was a secondary measure [3]. No study of acne in people taking DIM was located. Rat and lab findings do not show what happens in people [7][8].

MinoxidilLimited

Low-dose sublingual against placebo

Small trials found sublingual 1.35 mg twice daily raised front scalp hair count over placebo, with no change at the crown.

Testosterone levels did not change and no serious adverse events occurred.

The numbers and sources

Effect: At 24 weeks, sublingual minoxidil 1.35 mg twice daily raised midfrontal hair count 15.7 hairs per cm² more than placebo (P 0.03). Vertex hair count did not differ. Testosterone levels did not change and no serious adverse events occurred [8]. In men in a 24-week trial, mean hair fiber diameter fell 2 µm on placebo and on 0.45 mg daily, and rose 3 µm on 1.35 mg and 6 µm on 4.05 mg in an open-label extension [9].
Population: 46 transgender people on full-dose testosterone with mild androgenetic alopecia [8]; 33 men with androgenetic alopecia, plus 12 in the extension [9].
Sources: [8], [9]
Caveats: Two small trials. The higher doses in [9] were open-label and not compared with placebo. Sublingual minoxidil is not an FDA-approved form.

Saw palmettoLimitedStudied in men

Testosterone

Limited evidence: blood testosterone did not change after 30 days in 20 men with an enlarged prostate. Prostate tissue studies found less DHT on saw palmetto.

Compared with before treatment, in the same men [10]; untreated men having the same surgery [11]; placebo [12]

In prostate tissue from men given 320 mg a day for 3 months, DHT was lower and testosterone higher than in untreated men, mainly in the periurethral region.

The numbers and sources

Effect: In 20 men aged 50 to 75 with an enlarged prostate, 160 mg twice a day for 30 days did not change plasma testosterone, FSH or LH [10]. In prostate tissue from men given 320 mg a day for 3 months, DHT was lower and testosterone higher than in untreated men, mainly in the periurethral region [11]. In a 6-month randomized trial of a saw palmetto herbal blend, prostate tissue DHT fell modestly but significantly against placebo [12].
Population: 20 men with benign prostatic hyperplasia, mean age 67 [10]. Men having prostate surgery, treated or untreated [11]. 40 men with benign prostatic hyperplasia [12].
Sources: [10], [11], [12]
Caveats: The blood hormone study was small, short and had no control group [10]. The tissue studies measured hormones inside the prostate, not in the blood, and one tested a herbal blend [12]. No study in men without prostate disease was located.

Type in your own result

How it compares with the reference method

Mixed results2

Moderate

Immunoassays against mass spectrometry

Mixed results: immunoassays separated low from normal levels in men, read up to 99 ng/dL apart from mass spectrometry, and overread women's samples by 46% on average.

The numbers and sources

Compared with: Liquid or gas chromatography with mass spectrometry
Effect: In samples from 62 men with normal and 60 men with low testosterone, six immunoassay methods correlated with mass spectrometry at 0.92 to 0.97, and with most methods over 60% of results in the adult male range fell within 20% of it. One automated assay read a mean 90 ng/dL lower and another 99 ng/dL higher. The authors concluded the assays can tell normal from low levels in men when each laboratory sets its own reference range, and cannot accurately measure the levels found in women [29]. Across 10 immunoassays, 7 overestimated testosterone in women's samples, with mean results 46% above mass spectrometry, and results in men averaged 12% below it [13]. In a later accuracy survey, 142 laboratories using 16 immunoassays and mass spectrometry methods measured four donor sera. Bias ran from -17.8% to 73.1% at a target of 15.5 ng/dL and from -22.1% to 6.8% at 498 ng/dL, and 73% of laboratories had at least 3 of 4 results within 25.1% of the target [30].
Population: 122 men [29]. 50 men, 55 women and 11 children [13]. 142 clinical laboratories certified by New York State [30].
Sources: [29], [13], [30]
Caveats: The two assay comparisons date from 2003 and 2004, so the assays may since have changed. The Endocrine Society states that harmonized reference ranges apply only to assays certified by the Centers for Disease Control and Prevention [2].

LimitedStudied in men

Variation from one test to the next

Limited evidence: two hormone results from the same man differed by more than 18 to 28% about half the time, and 30% of low results were normal on repeat.

The numbers and sources

Compared with: The same man's earlier result
Effect: In men sampled up to six times over 6 months, the within-person variation of eleven hormone measures, total and free testosterone among them, implied that two measurements would differ by more than 18 to 28% about half the time and by more than 27 to 54% about a quarter of the time, depending on the hormone. Day to day biological variation accounted for more of the total than assay variation. The authors concluded that one sample is generally not sufficient and more than three is probably not warranted [31]. The Endocrine Society states that 30% of men with an initial level in the hypogonadal range have a normal level on repeat measurement [2].
Population: 132 men aged 30 to 79 in Boston, 121 of whom completed all six visits [31].
Sources: [31], [2]
Caveats: The percentage ranges cover all eleven hormone measures studied, and the abstract does not give the figure for testosterone alone [31].

Did not match the reference method2

LimitedStudied in men

Time of day

One study found testosterone 20 to 25% lower at 4 p.m. than at 8 a.m. in men aged 30 to 40, and 10% lower at age 70.

The numbers and sources

Compared with: A blood sample drawn at 8 a.m. from the same men
Effect: In men sampled on three mornings and three afternoons, testosterone at 4 p.m. was 20 to 25% lower than at 8 a.m. at ages 30 to 40, and 10% lower at age 70. Seventeen men had at least one afternoon result below 300 ng/dL while all three of their morning results were normal [27]. Guidelines differ on the window: two measurements in the early morning for the American Urological Association, 07:00 to 10:00 for the European Association of Urology and 07:00 to 11:00 for an earlier joint statement [3][5][7].
Population: 66 men aged 30 to 80 in Boston who completed at least five visits [27].
Sources: [27], [3], [5], [7]
Caveats: One study of 66 men. The authors conclude that the result supports restricting measurement to morning hours in both young and older men [27].

LimitedStudied in men

Fasting against not fasting

One study found a glucose drink lowered testosterone by 25% within 2 hours, and guidelines disagree on whether the test requires fasting.

The numbers and sources

Compared with: The same men's fasting sample
Effect: In 74 men given a 75 g oral glucose load, mean testosterone fell 25% and remained lower at 120 minutes (13.7 against 16.5 nmol/L at baseline). Of 66 men with normal levels at baseline, 10 (15%) fell below 9.7 nmol/L at one or more time points [28]. The Endocrine Society and the European Association of Urology call for a fasting morning sample [2][5]. The American Urological Association judges the evidence that food affects testosterone to be particularly weak and does not ask clinicians to insist on fasting [3]. The British Society for Sexual Medicine cites levels up to 30% higher when fasting, cites one UK review of 213 patients that found no significant effect, and takes a pragmatic approach [6].
Population: 74 men aged 19 to 74 with normal glucose tolerance, impaired glucose tolerance or newly found type 2 diabetes [28].
Sources: [28], [2], [5], [3], [6]
Caveats: One study of a glucose drink, not an ordinary meal. The fall did not differ by glucose tolerance or body mass index [28].

What studies tie it to

Linked in research4

StrongStudied in men

Death from any cause in men

Linked to more deaths in men at low testosterone: below 213 ng/dL for death from any cause and below 153 ng/dL for cardiovascular death in pooled cohorts.

The numbers and sources

Effect: In pooled individual data from cohorts that measured testosterone by mass spectrometry, men with baseline total testosterone below 7.4 nmol/L (213 ng/dL) had higher mortality from any cause, and men below 5.3 nmol/L (153 ng/dL) had higher cardiovascular mortality [16]. An earlier meta-analysis of 11 studies of death from any cause and 7 of cardiovascular death found low testosterone associated with both, with considerable differences between studies that tracked the men's age and testosterone levels, the length of follow-up and the time of day of sampling [17].
Population: 9 cohorts with individual data covering 255,830 participant-years, plus 11 studies with summary estimates [16]. 16,184 men for death from any cause and 11,831 for cardiovascular death, mean age 61, mean follow-up 9.7 years [17].
Sources: [16], [17]
Caveats: Observational. The earlier analysis concluded that the differences between studies suggest effects driven by the underlying health of the cohorts, so low testosterone may mark illness [17].

Moderate

Type 2 diabetes

Shown in genetic and cohort studies to run in opposite directions by sex: higher testosterone went with less type 2 diabetes in men and more in women.

The numbers and sources

Effect: In a meta-analysis of 43 studies, men with type 2 diabetes had lower testosterone than controls (mean difference -76.6 ng/dL, 95% CI -99.4 to -53.6) and women with diabetes had higher (6.1 ng/dL, 2.3 to 10.1). In prospective studies, men with higher testosterone, 449.6 to 605.2 ng/dL, had a 42% lower risk (relative risk 0.58, 0.39 to 0.87) [18]. In a genetic study, each standard deviation of genetically higher testosterone raised the odds of type 2 diabetes in women (odds ratio 1.37, 1.22 to 1.53) and lowered them in men (0.86, 0.76 to 0.98) [19]. In a 2-year trial in men with testosterone of 14.0 nmol/L or lower and impaired glucose tolerance or new diabetes, 12% of the testosterone group and 21% of the placebo group had diabetes on a glucose tolerance test at the end (relative risk 0.59, 0.43 to 0.80) [20].
Population: 6,427 men and 6,974 women in 43 prospective and cross-sectional studies [18]. 425,097 UK Biobank participants [19]. 1,007 men aged 50 to 74 with a waist of 95 cm or more, all enrolled in a lifestyle program [20].
Sources: [18], [19], [20]
Caveats: The cohort findings are observational. The trial's authors report that rises in hematocrit might limit treatment and that durability and cardiovascular effects remain to be studied [20].

LimitedStudied in men

Fractures in a trial that raised testosterone

One trial found more fractures, not fewer, when testosterone was raised in men with low levels: 3.5% against 2.5% on placebo over 3 years.

The numbers and sources

Effect: In a fracture substudy of the same cardiovascular trial, a clinical fracture occurred in 91 of 2,601 men on testosterone gel (3.50%) and 64 of 2,603 on placebo (2.46%), a hazard ratio of 1.43 (95% CI 1.04 to 1.97). Fracture incidence also appeared higher with testosterone for all other fracture end points [24].
Population: 5,204 men aged 45 to 80 with two morning testosterone levels below 300 ng/dL, median follow-up 3.19 years [24].
Sources: [24]
Caveats: A marker that tracks an outcome is not always one whose correction changes it. The authors note that testosterone treatment had improved bone density in earlier studies, and this result ran the other way [24].
Why limited: This rests on one trial, of 5,204 people. Strength counts independent studies that agree, so one trial is limited at any size.

Limited

Polycystic ovary syndrome in a genetic study of women

One genetic study found each standard deviation of genetically higher testosterone raised the odds of polycystic ovary syndrome in women by about half.

The numbers and sources

Effect: In a Mendelian randomization analysis, a genetically determined 1 standard deviation higher testosterone raised the odds of polycystic ovary syndrome in women (odds ratio 1.51, 95% CI 1.33 to 1.72). The authors also report adverse effects of higher testosterone on breast and endometrial cancers in women and on prostate cancer in men, without figures in the abstract [19].
Population: 425,097 UK Biobank participants, with 2,571 genome-wide significant associations for testosterone and related traits [19].
Sources: [19]
Caveats: One genetic study. Genetic estimates describe lifelong differences, not the effect of changing the level later in life.

Mixed results2

LimitedStudied in men

Sexual function, vitality and walking in a trial that raised testosterone in older men

One trial found raising low testosterone in men 65 and older improved sexual function moderately, with no benefit for vitality or walking distance.

The numbers and sources

Effect: In 790 men aged 65 or older with testosterone below 275 ng/dL and symptoms, testosterone gel for 1 year raised levels to the mid-normal range for men aged 19 to 40. Sexual activity increased (P below 0.001), as did sexual desire and erectile function. The share of men gaining at least 50 meters in the 6-minute walk did not differ significantly in the Physical Function Trial, and was 20.5% against 12.6% when men from all three trials were pooled. There was no significant benefit for vitality, and mood and depressive symptoms were slightly better [21].
Population: 790 men aged 65 or older, mean of two testosterone results below 275 ng/dL, treated for 1 year [21].
Sources: [21]
Caveats: One trial of 1 year. The authors state that it enrolled too few men to draw conclusions about the risks of treatment [21].

Moderate

Sexual function in women

Mixed results: women's testosterone levels did not track sexual function in one survey, while testosterone treatment improved sexual function in trials of postmenopausal women.

The numbers and sources

Effect: In a community survey of 1,021 Australian women aged 18 to 75, no clinically significant relationship was found between a low score in any domain of sexual function and a low total or free testosterone, and the authors concluded that no single androgen level predicts low sexual function [25]. In a meta-analysis of 36 randomized trials, testosterone treatment in postmenopausal women increased satisfactory sexual events (mean difference 0.85, 95% CI 0.52 to 1.18) and sexual desire (standardized mean difference 0.36, 0.22 to 0.50). Acne and hair growth were more likely, and oral testosterone raised LDL cholesterol [26].
Population: 1,021 women drawn at random from the electoral roll in Victoria, Australia [25]. 8,480 participants in 36 trials of at least 12 weeks [26].
Sources: [25], [26]
Caveats: The survey is cross-sectional. The trials tested treatment in women with low sexual desire, not a blood level, and the authors call for study of long-term effects [26].

Checked, no link found1

LimitedStudied in men

Heart attack and stroke in trials that raised testosterone

One trial found raising testosterone in men with levels below 300 ng/dL did not change heart attack, stroke or cardiovascular death over 33 months.

The numbers and sources

Effect: In 5,246 men aged 45 to 80 with symptoms, two fasting testosterone levels below 300 ng/dL and existing or high risk of cardiovascular disease, a first major cardiac event occurred in 7.0% on testosterone gel and 7.3% on placebo (hazard ratio 0.96, 95% CI 0.78 to 1.17), which met the trial's test for noninferiority. Atrial fibrillation, acute kidney injury and pulmonary embolism were more frequent in the testosterone group [22]. In a 1-year imaging substudy of an earlier trial, noncalcified coronary plaque volume grew more with testosterone than with placebo (estimated difference 41 cubic millimeters, 95% CI 14 to 67), with no major cardiovascular events in either group [23].
Population: 5,246 men, mean treatment 21.7 months and mean follow-up 33.0 months [22]. 138 men aged 65 or older who completed coronary imaging [23].
Sources: [22], [23]
Caveats: The trial was funded by a maker of testosterone gel and others, and treatment lasted under 2 years on average [22]. In cohorts, very low testosterone went with more cardiovascular deaths [16], which this trial did not reduce.
Why limited: This rests on one trial, of 5,246 people. Strength counts independent studies that agree, so one trial is limited at any size.

Sources

US Food and Drug Administration. 21 CFR 862.1680, Testosterone test system. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-862.1680
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Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. Journal of Urology. 2018. https://doi.org/10.1016/j.juro.2018.03.115
Travison TG, Vesper HW, Orwoll E, et al. Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe. The Journal of Clinical Endocrinology and Metabolism. 2017. https://doi.org/10.1210/jc.2016-2935
European Association of Urology. EAU Guidelines on Sexual and Reproductive Health, chapter 3, Male Hypogonadism. 2026 edition. https://uroweb.org/guidelines/sexual-and-reproductive-health/chapter/male-hypogonadism
Hackett G, Kirby M, Rees RW, et al. The British Society for Sexual Medicine Guidelines on Male Adult Testosterone Deficiency, with Statements for Practice. The World Journal of Men's Health. 2023. https://doi.org/10.5534/wjmh.221027
Wang C, Nieschlag E, Swerdloff R, et al. Investigation, treatment and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA and ASA recommendations. European Journal of Endocrinology. 2008. https://doi.org/10.1530/eje-08-0601
Wu FCW, Tajar A, Beynon JM, et al. Identification of Late-Onset Hypogonadism in Middle-Aged and Elderly Men. New England Journal of Medicine. 2010. https://doi.org/10.1056/nejmoa0911101
Bhasin S, Pencina M, Jasuja GK, et al. Reference Ranges for Testosterone in Men Generated Using Liquid Chromatography Tandem Mass Spectrometry in a Community-Based Sample of Healthy Nonobese Young Men in the Framingham Heart Study and Applied to Three Geographically Distinct Cohorts. The Journal of Clinical Endocrinology and Metabolism. 2011. https://doi.org/10.1210/jc.2010-3012
US National Library of Medicine. Testosterone test. MedlinePlus Medical Encyclopedia. Reviewed January 25, 2026. https://medlineplus.gov/ency/article/003707.htm
American Board of Internal Medicine. ABIM Laboratory Test Reference Ranges. January 2026. https://www.abim.org/Media/bfijryql/laboratory-reference-ranges.pdf
Zhu A, Andino J, Daignault-Newton S, et al. What Is a Normal Testosterone Level for Young Men? Rethinking the 300 ng/dL Cutoff for Testosterone Deficiency in Men 20-44 Years Old. Journal of Urology. 2022. https://doi.org/10.1097/ju.0000000000002928
Taieb J, Mathian B, Millot F, et al. Testosterone Measured by 10 Immunoassays and by Isotope-Dilution Gas Chromatography-Mass Spectrometry in Sera from 116 Men, Women, and Children. Clinical Chemistry. 2003. https://doi.org/10.1373/49.8.1381
Braunstein GD, Reitz RE, Buch A, et al. Testosterone Reference Ranges in Normally Cycling Healthy Premenopausal Women. The Journal of Sexual Medicine. 2011. https://doi.org/10.1111/j.1743-6109.2011.02380.x
Haring R, Hannemann A, John U, et al. Age-Specific Reference Ranges for Serum Testosterone and Androstenedione Concentrations in Women Measured by Liquid Chromatography-Tandem Mass Spectrometry. The Journal of Clinical Endocrinology and Metabolism. 2012. https://doi.org/10.1210/jc.2011-2134
Yeap BB, Marriott RJ, Dwivedi G, et al. Associations of Testosterone and Related Hormones With All-Cause and Cardiovascular Mortality and Incident Cardiovascular Disease in Men: Individual Participant Data Meta-analyses. Annals of Internal Medicine. 2024. https://doi.org/10.7326/m23-2781
Araujo AB, Dixon JM, Suarez EA, et al. Endogenous Testosterone and Mortality in Men: A Systematic Review and Meta-Analysis. The Journal of Clinical Endocrinology and Metabolism. 2011. https://doi.org/10.1210/jc.2011-1137
Ding EL, Song Y, Malik VS, et al. Sex Differences of Endogenous Sex Hormones and Risk of Type 2 Diabetes: A Systematic Review and Meta-analysis. JAMA. 2006. https://doi.org/10.1001/jama.295.11.1288
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Caronia LM, Dwyer AA, Hayden D, et al. Abrupt decrease in serum testosterone levels after an oral glucose load in men: implications for screening for hypogonadism. Clinical Endocrinology. 2013. https://doi.org/10.1111/j.1365-2265.2012.04486.x
Wang C, Catlin DH, Demers LM, et al. Measurement of Total Serum Testosterone in Adult Men: Comparison of Current Laboratory Methods Versus Liquid Chromatography-Tandem Mass Spectrometry. The Journal of Clinical Endocrinology and Metabolism. 2004. https://doi.org/10.1210/jc.2003-031287
Cao ZT, Botelho JC, Rej R, Vesper H. Accuracy-based proficiency testing for testosterone measurements with immunoassays and liquid chromatography-mass spectrometry. Clinica Chimica Acta. 2017. https://doi.org/10.1016/j.cca.2017.03.010
Brambilla DJ, O'Donnell AB, Matsumoto AM, et al. Intraindividual variation in levels of serum testosterone and other reproductive and adrenal hormones in men. Clinical Endocrinology. 2007. https://doi.org/10.1111/j.1365-2265.2007.02976.x

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