Prolactin
Prolactin upper limits depend on sex, pregnancy and the assay, from about 15 to 23 ng/mL in men and 23 to 38 in nonpregnant women. Stress at the blood draw can raise the result two to four times, and about a fifth of high results reflect inactive macroprolactin. In trials, lowering high prolactin restored ovulation.
- Status
- A blood test ordered by a clinician and also sold direct to consumers by some US laboratories. FDA classifies prolactin test systems as class I devices [1].
- Measures
- The amount of prolactin in blood, a hormone released by the pituitary gland that stimulates breast development and milk production [2].
- Also called
- prolactin, PRL, serum prolactin, prolactin serum, prolactin blood test, prolactin level, total prolactin, lactogen
- Tested for
- irregular or absent periods, milky nipple discharge, infertility, low sex drive, erectile dysfunction, pituitary tumor workup, low testosterone workup
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 research3
- ModerateShown in a trial of women with high prolactin and no periods: the drug that normalized prolactin more often also restored ovulation more often, 72% against 52%.
- ModerateLinked to slightly more breast cancer at higher levels within the usual range, 16% more for the highest against the lowest levels in seven pooled studies.
- LimitedOne cohort found higher prolactin went with more deaths, 17% more per standard deviation in men and 22% more in women.
Reported risks1
Reference ranges
Each range is the one its source published, in ng/mL. Also reported in mIU/L. Where sources differ, each is shown.
US National Library of Medicine, MedlinePlus, nonpregnant women
Nonpregnant women · [2]
| Range | What the source calls it |
|---|---|
| below 25 ng/mL | "normal" |
| 25 or above ng/mL | No name given |
Printed as less than 25 ng/mL (25 µg/L), so the range has no lower band. MedlinePlus states that ranges may vary slightly among laboratories and names no assay. It notes that a high result may be repeated in the early morning after an 8-hour fast [2].
Earll and colleagues, 2024, Roche Elecsys Prolactin II assay, women
Women aged 18 to 50 not using hormonal contraception, measured with the Roche Elecsys Prolactin II assay · [3]
| Range | What the source calls it |
|---|---|
| below 5.3 ng/mL | No name given |
| 5.3 to 37.8 ng/mL | "reference interval" |
| above 37.8 ng/mL | No name given |
A nonparametric reference interval from leftover samples of 125 outpatients in southeast Wisconsin whom the study screened for conditions and medicines that change prolactin, drawn at any stage of the menstrual cycle. The 90% confidence interval of the upper limit was 30 to 55 ng/mL. The interval the manufacturer supplies for the same assay is 4.8 to 23.3 ng/mL, and the authors argue that its upper limit is too low. The study did not set intervals for women after menopause [3].
Earll and colleagues, 2024, Siemens prolactin assay, women
Women aged 18 to 50 not using hormonal contraception, measured with the Siemens Atellica prolactin assay · [3]
| Range | What the source calls it |
|---|---|
| below 3.8 ng/mL | No name given |
| 3.8 to 23.6 ng/mL | "reference interval" |
| above 23.6 ng/mL | No name given |
From the same 125 women, measured on a second assay. The interval the manufacturer supplies is 2.8 to 29.2 ng/mL, and the authors judged their own to match it. See the Roche block for how the study was done [3].
Earll and colleagues, 2024, Roche Elecsys Prolactin II assay, women using estrogen-containing contraceptives
Women aged 18 to 50 using combined ethinyl estradiol and progestin contraceptives, measured with the Roche Elecsys Prolactin II assay · [3]
| Range | What the source calls it |
|---|---|
| below 5 ng/mL | No name given |
| 5 to 51.5 ng/mL | "reference interval" |
| above 51.5 ng/mL | No name given |
From 122 women using a pill, vaginal ring or patch. Printed as 5.0 to 51.5 ng/mL. The authors caution that the higher upper limit rests on two samples above 50 ng/mL, that the spread of results otherwise looked like that of women not using these contraceptives, and that their own laboratory applies the interval for women not using them to all women [3].
Earll and colleagues, 2024, Siemens prolactin assay, women using estrogen-containing contraceptives
Women aged 18 to 50 using combined ethinyl estradiol and progestin contraceptives, measured with the Siemens Atellica prolactin assay · [3]
| Range | What the source calls it |
|---|---|
| below 3.5 ng/mL | No name given |
| 3.5 to 30.9 ng/mL | "reference interval" |
| above 30.9 ng/mL | No name given |
From the same 122 women, measured on a second assay. See the Roche block for women using these contraceptives [3].
US National Library of Medicine, MedlinePlus, pregnant women
Pregnant women · [2]
| Range | What the source calls it |
|---|---|
| below 500 ng/mL | "normal" |
| 500 or above ng/mL | No name given |
Printed as less than 500 ng/mL (500 µg/L), with no lower band and no stage of pregnancy stated. It names no assay [2].
US National Library of Medicine, MedlinePlus, men
Men · [2]
| Range | What the source calls it |
|---|---|
| below 20 ng/mL | "normal" |
| 20 or above ng/mL | No name given |
Printed as less than 20 ng/mL (20 µg/L), so the range has no lower band. It names no assay [2].
Earll and colleagues, 2024, Roche Elecsys Prolactin II assay, men
Men aged 18 to 50, measured with the Roche Elecsys Prolactin II assay · [3]
| Range | What the source calls it |
|---|---|
| below 4.2 ng/mL | No name given |
| 4.2 to 22.8 ng/mL | "reference interval" |
| above 22.8 ng/mL | No name given |
A nonparametric reference interval from leftover samples of 127 male outpatients in southeast Wisconsin. The 90% confidence interval of the upper limit was 17.6 to 26.9 ng/mL. The interval the manufacturer supplies for the same assay is 4.0 to 15.2 ng/mL, and the authors argue that its upper limit is too low [3].
Earll and colleagues, 2024, Siemens prolactin assay, men
Men aged 18 to 50, measured with the Siemens Atellica prolactin assay · [3]
| Range | What the source calls it |
|---|---|
| below 2.9 ng/mL | No name given |
| 2.9 to 14.5 ng/mL | "reference interval" |
| above 14.5 ng/mL | No name given |
From the same 127 men, measured on a second assay. The interval the manufacturer supplies is 2.1 to 17.7 ng/mL, and the authors judged their own to match it [3].
What has been shown to move it
Shown to lower it1
Cyclic breast pain
Shown to ease cyclic breast pain against placebo, with a moderate effect, and to lower raised prolactin in women of reproductive age.
Compared with placebo [5]; dopamine agonists, NSAIDs, serotonin reuptake inhibitors and hormonal contraceptives [5]
It lowered raised serum prolactin, and 7 trials found it not inferior to dopamine agonists, NSAIDs, serotonin reuptake inhibitors or hormonal contraceptives.
The numbers and sources
- Effect
- In 6 placebo-controlled studies, vitex reduced breast pain intensity (SMD 0.67, 95% CI 0.5 to 0.85). It lowered raised serum prolactin, and 7 trials found it not inferior to dopamine agonists, NSAIDs, serotonin reuptake inhibitors or hormonal contraceptives [5].
- Population
- 718 women aged 18 to 45 in the pooled studies, among 25 studies in the review [5].
- Sources
- [5]
- Caveats
- Risk of bias was unclear in most studies [5].
Tested, and not shown to change it1
Breast milk supply
Small trials found more breast milk than placebo. In mothers of preterm infants, the day 7 difference was gone by day 15.
Prolactin, infant weight and breastfeeding satisfaction did not differ.
The numbers and sources
- Effect
- In a network meta-analysis of 4 studies, fenugreek increased breast milk volume over placebo (11.11, 95% CI 6.77 to 15.46). Coleus amboinicus and palm date produced larger effects than fenugreek [8]. In a 2025 trial of 68 mothers of infants born before 32 weeks, 500 mg three times a day from day 5 to day 14 after delivery gave higher milk volume than placebo on day 7 (p 0.017) but not on day 15 (p 0.073). Prolactin, infant weight and breastfeeding satisfaction did not differ [9].
- Population
- 122 lactating women on fenugreek across 5 studies [8]; 68 mothers of preterm infants in Iran [9].
- Sources
- [8], [9]
- Caveats
- Few small studies, and the abstract of [8] does not state the unit of the milk volume estimate. The preterm trial lasted 10 days, and its day 7 difference was gone by day 15 [9].
How it compares with the reference method
Mixed results1
Variation from one test to the next
Small studies found prolactin varied about 13% within a man over 10 weeks and 58% within a woman over a year.
The numbers and sources
- Compared with
- The same person's earlier results
- Effect
- In 38 men sampled weekly for 10 weeks, the within-person variation of prolactin was 13% [15]. In 21 women sampled monthly for a year it was 58% within a woman and 63% between women, with variation both by season and within a day [16].
- Population
- 38 men in the European Biological Variation Study [15]. 21 women [16].
- Sources
- [15], [16]
- Caveats
- Small studies with different sampling schedules, so the two figures are not directly comparable.
Did not match the reference method3
Macroprolactin
Shown to overstate active prolactin when macroprolactin is present: it fully explained 22% to 24% of high results in two laboratory series.
The numbers and sources
- Compared with
- Prolactin measured after polyethylene glycol precipitation, which removes macroprolactin
- Effect
- Macroprolactin is a large form of prolactin that immunoassays detect and that has little activity in the body. In one center, 453 of 2,089 high samples (22%) were explained entirely by it, a similar share at every level of total prolactin, and patients with macroprolactin could not be told apart by clinical features alone [10]. In another series it accounted for 24% of 300 high samples, and when ten such samples went to 18 laboratories, the results from nine assay systems differed by 2.3 to 7.8 times [11]. A Pituitary Society consensus puts large forms of prolactin in 10% to 25% of people with high prolactin [12]. Prolactin measured after precipitation is a different quantity from the total prolactin on this page, with its own intervals, for example 63 to 245 mIU/L in men and 75 to 381 mIU/L in women on one assay [13].
- Population
- 2,089 high samples over 5 years in one center [10]. 300 high samples and 18 laboratories [11]. 53 men and 93 women for the intervals after precipitation [13].
- Sources
- [10], [11], [12], [13]
- Caveats
- The two series share authors and date from 2002 and 2005, so the assays may since have changed. A standard lab report of total prolactin does not show whether macroprolactin is present.
Stress at the blood draw and timing
One study found 27% of people referred for a high prolactin had a normal level when the sample was repeated through a cannula, at once or after rest.
The numbers and sources
- Compared with
- A repeat sample drawn through a cannula, immediately and after 120 minutes of bed rest
- Effect
- Of 235 people referred after one raised prolactin, 64 (27%) were within the normal range on retesting: 41 (17%) on the sample drawn straight after the cannula was placed and 23 (9%) after 120 minutes of rest. Referral levels overlapped widely between people whose level stayed high and those whose level did not, and a referral level of 2,000 mU/L (94 ng/mL) was 97% specific for a level that stayed high [14]. A Pituitary Society consensus states that stress, for example from the needle, can raise prolactin two to four times for less than an hour, and that exercise, high-protein meals and alcohol can raise it [12]. MedlinePlus lists stress, high-protein meals, recent exercise and breast stimulation as temporary causes [2].
- Population
- 235 patients at one center from 2000 to 2010, referred with prolactin above 19 ng/mL in men or 24 ng/mL in women and below 260 ng/mL [14].
- Sources
- [14], [12], [2]
- Caveats
- One retrospective study at one center, which excluded people with known pituitary disease, dopamine antagonist use or macroprolactin [14].
Agreement between assays
One study found two widely used prolactin assays disagreed on the same samples, with upper reference limits of 37.8 and 23.6 ng/mL in women.
The numbers and sources
- Compared with
- A second prolactin immunoassay run on the same specimens
- Effect
- On the same 374 specimens, the upper limit of the reference interval was 37.8 ng/mL in women and 22.8 in men on the Roche assay, and 23.6 and 14.5 on the Siemens assay. The regression slopes between the two assays were 1.52 to 1.63, in line with earlier work that had found Roche results about 50% higher. The manufacturers' own upper limits ran the other way, 23.3 and 15.2 ng/mL for Roche against 29.2 and 17.7 for Siemens [3]. A Pituitary Society consensus states that diagnosis depends on assay-specific and sex-specific reference intervals [12].
- Population
- 374 leftover specimens from outpatients aged 18 to 50 in Wisconsin [3].
- Sources
- [3], [12]
- Caveats
- One study of two assays. The consensus also describes a rare assay artifact, the hook effect, in which a very high prolactin reads as only moderately raised [12].
What studies tie it to
Linked in research3
Periods and ovulation in trials that lowered high prolactin
Shown in a trial of women with high prolactin and no periods: the drug that normalized prolactin more often also restored ovulation more often, 72% against 52%.
The numbers and sources
- Effect
- In women with high prolactin and absent periods, prolactin became stably normal in 83% on cabergoline and 59% on bromocriptine, and 72% against 52% had ovulatory cycles or became pregnant. Absent periods persisted in 7% and 16%. Adverse effects were recorded in 68% and 78% [4]. A systematic review found that dopamine agonists, against no treatment, reduced the prolactin level and the likelihood of persistently high prolactin (relative risk 0.90, 95% CI 0.81 to 0.99), and that cabergoline did more than bromocriptine to reduce persistently high prolactin, absent or infrequent periods and milky discharge [5].
- Population
- 459 women, most with a small prolactin-secreting pituitary tumor or no cause found, treated for 24 weeks [4]. 8 randomized and 178 nonrandomized studies with more than 3,000 patients [5].
- Sources
- [4], [5]
- Caveats
- The trial compared two drugs and had no placebo group. It enrolled women with high prolactin and absent periods, so it does not describe mildly raised results found without symptoms [4].
Breast cancer
Linked to slightly more breast cancer at higher levels within the usual range, 16% more for the highest against the lowest levels in seven pooled studies.
The numbers and sources
- Effect
- In a meta-analysis of seven studies, the highest against the lowest prolactin levels had a pooled relative risk of breast cancer of 1.16 (95% CI 1.04 to 1.29). The association appeared in postmenopausal women and for hormone receptor positive tumors, and not in premenopausal women [6]. In two cohorts of US nurses, prolactin above 15.7 ng/mL against 8.1 ng/mL or below, measured less than 10 years before diagnosis, had a relative risk of 1.20 (1.03 to 1.40). Levels measured 10 or more years before diagnosis showed no association (0.97). In postmenopausal women the relative risk was 1.37 [7].
- Population
- 7 observational studies [6]. 2,468 women with breast cancer and 4,021 controls with a sample from less than 10 years before diagnosis [7].
- Sources
- [6], [7]
- Caveats
- Observational. The cut points are quarters of the study's own participants and sit inside the ranges printed above [7].
Death from any cause
One cohort found higher prolactin went with more deaths, 17% more per standard deviation in men and 22% more in women.
The numbers and sources
- Effect
- Each standard deviation higher prolactin had a hazard ratio for death from any cause of 1.17 in men (95% CI 1.07 to 1.29) and 1.22 in women (1.03 to 1.46). The top third against the bottom third had 1.75 in men (1.32 to 2.32) and 1.66 in women (1.08 to 2.56). Cardiovascular deaths followed the same pattern in both sexes [8].
- Population
- 3,929 adults aged 20 to 81 in a German population study, 419 deaths over a median 10.1 years [8].
- Sources
- [8]
- Caveats
- One observational cohort, described by its authors as the first report of this association [8].
Mixed results1
Type 2 diabetes
Mixed results: higher prolactin within the normal range went with less existing type 2 diabetes and was not tied to new cases in one meta-analysis.
The numbers and sources
- Effect
- For the top against the bottom quarter of prolactin, the odds of already having type 2 diabetes were 0.52 in men (95% CI 0.35 to 0.77) and 0.46 in women (0.30 to 0.73). For new cases the relative risks were 1.21 in men (0.79 to 1.87) and 0.77 in women (0.48 to 1.22) [9].
- Population
- 6 studies: cross-sectional studies of 6,670 people and longitudinal studies of 13,203 [9].
- Sources
- [9]
- Caveats
- The association appeared only in cross-sectional data, and the authors state that further studies are needed to address whether it is causal [9].
Risks
Reported risks1
Further testing after a result just above the laboratory's upper limit
One hospital review found 298 people with results just above one assay's upper limit had 39 MRI scans and 28 specialist referrals, with no new prolactin disorder identified.
The numbers and sources
- How common
- How often is not known: the sources give no rate.
- Effect
- Over 6 months, 298 patients had a prolactin result between the manufacturer's upper limit for the Roche assay and the higher limit the study derived. No cases of clinically significant prolactin excess were identified among them beyond people already diagnosed and under routine monitoring. The further evaluation the authors judged unnecessary included 459 repeat prolactin tests, 57 macroprolactin tests, 39 MRI studies and 28 endocrine referrals, and 11 patients received dopamine agonist drugs. The minimum cost at Medicare rates was $34,134 [3].
- Population
- 206 women and 92 men at one US center, January to June 2022 [3].
- Sources
- [3]
- Caveats
- One retrospective chart review at one center with one assay. The authors acknowledge that a person with a true prolactin disorder could in theory present below their higher limit [3].
Sources
- US Food and Drug Administration. 21 CFR 862.1625, Prolactin (lactogen) test system. Electronic Code of Federal Regulations. https://www.ecfr.gov/current/title-21/section-862.1625
- US National Library of Medicine. Prolactin blood test. MedlinePlus Medical Encyclopedia. Reviewed July 21, 2024. https://medlineplus.gov/ency/article/003718.htm
- Earll E, Javorsky BR, Sarvaideo J, Straseski JA, Nerenz RD. Clinical Impact of New Reference Intervals for the Roche Prolactin II Immunoassay. Journal of the Endocrine Society. 2024. https://doi.org/10.1210/jendso/bvae069
- Webster J, Piscitelli G, Polli A, et al. A Comparison of Cabergoline and Bromocriptine in the Treatment of Hyperprolactinemic Amenorrhea. New England Journal of Medicine. 1994. https://doi.org/10.1056/nejm199410063311403
- Wang AT, Mullan RJ, Lane MA, et al. Treatment of hyperprolactinemia: a systematic review and meta-analysis. Systematic Reviews. 2012. https://doi.org/10.1186/2046-4053-1-33
- Wang M, Wu X, Chai F, Zhang Y, Jiang J. Plasma prolactin and breast cancer risk: a meta-analysis. Scientific Reports. 2016. https://doi.org/10.1038/srep25998
- Tworoger SS, Eliassen AH, Zhang X, et al. A 20-Year Prospective Study of Plasma Prolactin as a Risk Marker of Breast Cancer Development. Cancer Research. 2013. https://doi.org/10.1158/0008-5472.can-13-0665
- Haring R, Friedrich N, Völzke H, et al. Positive association of serum prolactin concentrations with all-cause and cardiovascular mortality. European Heart Journal. 2014. https://doi.org/10.1093/eurheartj/ehs233
- Faria de Castro L, Alves Dos Santos Á, Augusto Casulari L, et al. Association between variations of physiological prolactin serum levels and the risk of type 2 diabetes: A systematic review and meta-analysis. Diabetes Research and Clinical Practice. 2020. https://doi.org/10.1016/j.diabres.2020.108247
- Gibney J, Smith TP, McKenna TJ. The Impact on Clinical Practice of Routine Screening for Macroprolactin. The Journal of Clinical Endocrinology and Metabolism. 2005. https://doi.org/10.1210/jc.2004-2234
- Smith TP, Suliman AM, Fahie-Wilson MN, McKenna TJ. Gross Variability in the Detection of Prolactin in Sera Containing Big Big Prolactin (Macroprolactin) by Commercial Immunoassays. The Journal of Clinical Endocrinology and Metabolism. 2002. https://doi.org/10.1210/jc.2001-011943
- Petersenn S, Fleseriu M, Casanueva FF, et al. Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society international Consensus Statement. Nature Reviews Endocrinology. 2023. https://doi.org/10.1038/s41574-023-00886-5
- Beltran L, Fahie-Wilson MN, McKenna TJ, Kavanagh L, Smith TP. Serum Total Prolactin and Monomeric Prolactin Reference Intervals Determined by Precipitation with Polyethylene Glycol: Evaluation and Validation on Common Immunoassay Platforms. Clinical Chemistry. 2008. https://doi.org/10.1373/clinchem.2008.105312
- Whyte MB, Pramodh S, Srikugan L, et al. Importance of cannulated prolactin test in the definition of hyperprolactinaemia. Pituitary. 2015. https://doi.org/10.1007/s11102-014-0576-7
- Itkonen O, Jonker N, Aarsand AK, et al. The European biological variation study (EuBIVAS): Biological variation data for testosterone, follicle stimulating hormone, prolactin, luteinizing hormone and dehydroepiandrosterone sulfate in men. Clinica Chimica Acta. 2024. https://doi.org/10.1016/j.cca.2024.117806
- Garde AH, Hansen AM, Skovgaard LT, Christensen JM. Seasonal and Biological Variation of Blood Concentrations of Total Cholesterol, Dehydroepiandrosterone Sulfate, Hemoglobin A1c, IgA, Prolactin, and Free Testosterone in Healthy Women. Clinical Chemistry. 2000. https://doi.org/10.1093/clinchem/46.4.551