Iron and anemia
Everything in the library studied for it, medical and holistic together. Within each kind, what was shown to help comes first, strongest evidence first. What was tested and not shown to help stays on the list.
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
Medication
Anemia with fibroids: relugolix combination
Shown to raise hemoglobin by more than 2 g/dL in 44% and 55% of anemic women with fibroids, against 17% and 6% on placebo, in two trials.
Compared with placebo [2]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Among women with hemoglobin of 10.5 g/dL or less at the start, 44.2% (L1) and 55.0% (L2) on relugolix combination therapy gained more than 2 g/dL by week 24, against 17.2% and 5.7% on placebo [2]. A meta-analysis reported hemoglobin improved in 46.3% of patients [3].
- Population
- 43 and 40 anemic women on treatment against 29 and 53 on placebo, within 770 women [2]; 511 participants in 6 studies [3].
- Sources
- [2], [3]
- Caveats
- Iron was required for women with hemoglobin of 8 to 10 g/dL, and women under 8 g/dL were excluded [2].
Anemia with fibroids: elagolix with add-back
Shown to raise hemoglobin by more than 2 g/dL in 50% and 62% of anemic women with fibroids, against 16% and 21% on placebo, in two trials.
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- Among women with hemoglobin of 10.5 g/dL or less, 62% (UF-1) and 50% (UF-2) on elagolix with add-back gained more than 2 g/dL by month 6, against 16% and 21% on placebo. Over 90% of these women took iron [6]. A meta-analysis found more women met the hemoglobin end point on elagolix than on placebo [8].
- Population
- 52 and 48 anemic women on treatment against 31 and 24 on placebo [6]; 1,217 patients in 4 trials [8].
- Sources
- [6], [8]
- Caveats
- Nearly all anemic women also took iron, so the rise reflects the drug on top of iron [6].
Anemia before fibroid surgery: leuprolide and other GnRH agonists
Shown to raise hemoglobin before fibroid surgery, by about 0.9 g/dL against placebo or no treatment, and with iron 75% reached target levels against 49% on iron alone.
Compared with iron alone [10]; placebo or no pretreatment [11]
The numbers and sources
- How common
- Very common: more than 1 in 10 people.
- Effect
- In women with hematocrit of 30% or less or hemoglobin of 10.2 g/dL or less, Lupron Depot 3.75 mg monthly with iron raised hemoglobin by a mean 4.2 g/dL and hematocrit by 10.1% at 3 months. At week 12, 75% on leuprolide with iron reached hematocrit of 36% and hemoglobin of 12 g/dL, against 49% on iron alone [10]. Across 10 trials of GnRH agonists before surgery, preoperative hemoglobin rose 0.88 g/dL more than with placebo or no pretreatment (95% CI 0.68 to 1.08, I² 0%, moderate certainty) [11].
- Population
- 104 women on leuprolide with iron and 98 on iron alone [10]; 834 premenopausal women in 10 trials [11].
- Sources
- [10], [11]
- Caveats
- The Cochrane review pools GnRH agonists as a class, not leuprolide alone [11]. The label notes some women may benefit from iron alone or from 1 to 2 months of treatment [10].
Heavy periods (hormonal IUD)
Shown to lower heavy menstrual blood loss more than other medicines, about 67 mL more, with fewer treatment failures, on the levonorgestrel IUD in women with heavy periods.
Compared with oral progestins, combined pills, mefenamic acid, tranexamic acid or usual medical treatment [6]; medroxyprogesterone acetate [3]
The numbers and sources
- Effect
- Against other medical therapy, the levonorgestrel IUD lowered menstrual blood loss (MD 66.91 mL, 95% CI 42.61 to 91.20, low certainty), led to fewer treatment failures (RR 0.34) and fewer withdrawals (RR 0.49), and slightly raised quality of life [6]. In the label trial, Mirena reduced blood loss more than medroxyprogesterone acetate over 6 cycles [3].
- Population
- 2,511 women in 25 trials [6]; 160 women with blood loss of 80 mL or more [3].
- Sources
- [6], [3]
- Caveats
- Attrition bias and small numbers in several trials [6].
Hemoglobin before fibroid surgery
Shown to raise hemoglobin before fibroid surgery by about 0.9 g/dL more than placebo, in women taking SPRMs including ulipristal.
Compared with placebo [6]; GnRH agonists [6]
The numbers and sources
- Effect
- SPRMs raised preoperative hemoglobin by 0.93 g/dL against placebo (95% CI 0.52 to 1.34, 2 studies, 173 women, I² 0%, moderate certainty). Preoperative hemoglobin did not differ between GnRH agonists and other medicines including ulipristal (MD -0.02 g/dL, 95% CI -0.41 to 0.37, 242 women) [6].
- Population
- Premenopausal women before fibroid surgery in randomized trials [6].
- Sources
- [6]
- Caveats
- Two pooled trials, pooled across SPRMs. In one trial all women received iron [1].
Heavy bleeding with fibroids (hormonal IUD and combined pill)
Limited evidence: in women with fibroids, the hormonal IUD lowered bleeding and raised hemoglobin more than the combined pill in one small trial, without clearly shrinking fibroids.
Compared with a low-dose combined pill and oral norethisterone acetate [27]; the levonorgestrel IUD and placebo [28]; comparisons in 11 studies the source abstract does not describe [29]
The numbers and sources
- Effect
- In one trial of 44 women with fibroids, the levonorgestrel IUD reduced bleeding on the alkaline hematin test by 77.50% more than a low-dose combined pill (95% CI 70.44 to 84.56) and raised hemoglobin by 1.50 g/dL more (95% CI 0.85 to 2.15) at 12 months. Fibroid size did not clearly differ (MD 1.90%, 95% CI -12.24 to 16.04). Against oral norethisterone acetate, the IUD improved a visual bleeding score and raised hemoglobin by 10.14% more at 6 months, and spotting was more common (64.3% against 30%) [27]. A review of 2 trials found the combined pill did less than the levonorgestrel IUD for bleeding, quality of life and hemoglobin, and in a single trial at high risk of bias it shrank fibroids more than placebo [28]. A review of 11 studies of 10 to 104 women each found the levonorgestrel IUD reduced menstrual blood loss and raised hemoglobin, ferritin and hematocrit, with no evidence that fibroids shrank. Expulsion was uncommon and linked to fibroids larger than 3 cm [29].
- Population
- 221 premenopausal women with fibroids in 4 trials [27]; women with fibroids and heavy bleeding in 2 trials [28]; premenopausal women with symptomatic fibroids in 11 studies [29].
- Sources
- [27], [28], [29]
- Caveats
- The Cochrane reviewers rated all of this evidence very low quality and wrote that they were uncertain of the effects [27]. The combined pill findings rest on single trials [28]. The 11-study review abstract does not describe the studies' designs [29].
Anemia and hemoglobin
Limited evidence: trials have not reported whether tranexamic acid changes hemoglobin, and one small trial was too imprecise to show an effect on anemia.
Compared with placebo or standard care [2]
The numbers and sources
- Effect
- Of 17 trials, none reported adequate data on hemoglobin concentration. For anemia, one small trial contributed data (RR 0.15, 95% CI 0.01 to 2.74, very low certainty) [2].
- Population
- Women of reproductive age with normal or abnormal uterine bleeding in 17 randomized trials [2].
- Sources
- [2]
- Caveats
- The interval is so wide that both a large benefit and none are possible. The review's authors call for trials in menstruating women with anemia [2].
Supplements
Raising iron stores
Shown to raise ferritin in iron-deficient adults and athletes without anemia, most in those starting with very low ferritin.
The numbers and sources
- Effect
- In iron-deficient non-anemic endurance athletes, iron raised serum ferritin (Hedges' g 1.088, 95% CI 0.914 to 1.263) and hemoglobin (g 0.695) [1]. In 13 trials of athletes, oral iron raised ferritin (SMD 1.27, 95% CI 0.44 to 2.10) and did not significantly change hemoglobin (SMD 1.31, 95% CI -0.29 to 2.93) [2]. In non-anemic iron-deficient adults, ferritin rose by 9.23 (95% CI 6.48 to 11.97) and hemoglobin by 4.01 g/L [3].
- Population
- 17 studies of endurance athletes [1]; 449 athletes in 13 RCTs [2]; 1,170 patients in 18 trials [3].
- Sources
- [1], [2], [3]
- Caveats
- In [2], the ferritin rise was evident in athletes starting at 12 µg/L or below, with minimal effect at higher starting ferritin.
Anemia in pregnancy
Shown to halve anemia risk in non-anemic pregnant women, with no change in birth weight or preterm birth.
The numbers and sources
- Effect
- In 23 studies of 4,492 non-anemic pregnant women, oral iron raised hemoglobin by 6.95 g/L (95% CI 4.81 to 9.09) and ferritin by 12.22 ng/mL, and halved the risk of anemia (RR 0.50, 95% CI 0.34 to 0.74, high certainty, number needed to treat 10). Birth weight, preterm birth and cesarean section did not differ [7].
- Population
- Non-anemic pregnant women in RCTs and observational studies [7].
- Sources
- [7]
- Caveats
- Heterogeneity was high for hemoglobin (I² 91%) and ferritin (I² 87%). Reporting of harms was inconsistent, and the authors found too little evidence to judge them [7].
Iron deficiency anemia
Shown to raise serum iron, ferritin and hemoglobin more than ferrous sulfate in people with iron deficiency anemia.
The numbers and sources
- Effect
- Compared with ferrous sulfate, lactoferrin raised serum iron by 41.44 µg/dL and ferritin by 13.60 ng/mL more, and raised hemoglobin more. Fractional iron absorption was 2.08 percentage points lower and IL-6 was 45.59 pg/mL lower [5]. In 8 controlled trials in children with or without anemia, adding bovine lactoferrin to iron raised serum ferritin by 3.52 µg/L more than iron alone (95% CI 0.66 to 6.38), with no difference in hemoglobin, serum iron or transferrin receptor [6].
- Population
- Intervention studies in people with iron deficiency anemia [5]. Children in 8 trials [6].
- Sources
- [5], [6]
- Caveats
- The first abstract does not give the number of trials or participants [5]. The second compared lactoferrin plus iron with iron alone, not lactoferrin with iron [6].
Correcting B12 deficiency by mouth instead of injection
Shown to raise blood B12 by mouth about as well as injection in people with B12 deficiency. One small trial in children favored injection.
The numbers and sources
- Effect
- In two trials using 1,000 µg a day by mouth, blood B12 levels showed no clinically relevant difference from intramuscular injection. One trial using 2,000 µg a day by mouth found blood B12 680 pg/mL higher than injection (95% CI 392.7 to 967.3) [1]. Across 16 studies, serum B12 rose by a pooled 402.6 pg/mL (95% CI 293.6 to 511.5) and homocysteine fell by 4.83 µmol/L, with no significant difference between oral, sublingual and intramuscular routes (p = 0.270) and no dose relationship [2]. A 2026 review of 13 studies in adults found that all three routes raised serum B12, several with comparable or larger rises by mouth [3]. In a 2026 trial, hemoglobin recovery at 28 days did not differ by route after adjustment, comparing B12 given in the nose, into a vein or into muscle [4].
- Population
- 3 RCTs, 153 people with B12 deficiency, mean ages 38.6 to 72, treated for 3 to 4 months [1]; 16 RCTs and observational studies with 6,098 participants [2]; 13 studies of adults with an indication for replacement in 10 countries [3]; 153 adults with B12 deficiency anemia [4].
- Sources
- [1], [2], [3], [4]
- Caveats
- The Cochrane review rated its evidence low quality, and no trial reported symptoms of deficiency, quality of life or acceptability [1]. The 2025 meta-analysis pooled RCTs with observational studies, heterogeneity was above 80% in most comparisons, and it found signs of publication bias [2]. The 2026 review did not pool, judged every trial at some risk of bias, and was funded by Myralis Indústria Farmacêutica [3]. In children with deficiency anemia, the only trial, at high risk of bias, found larger rises in B12 and hemoglobin with injection [5]. Graded B rather than A because the 2025 meta-analysis mixed in observational studies and the 2026 review did not pool.
Fibroid size and heavy bleeding
One small trial found green tea extract shrank fibroids by about a third over 4 months in women with symptomatic fibroids. An uncontrolled study found no size change.
Compared with placebo capsules of brown rice [13]; before treatment, in the same women [14][15]
The numbers and sources
- Effect
- In a placebo-controlled trial, 800 mg a day of green tea extract (45% EGCG) for 4 months reduced total fibroid volume by 32.6%, while volume rose 24.3% on placebo (P 0.0001). Fibroid symptom severity fell 32.4% and quality of life rose 18.53% against placebo. In the green tea group, hemoglobin rose 0.7 g/dL (P 0.02) and average blood loss fell from 71 to 45 mL a month (P 0.001). No adverse effects or endometrial changes were seen in either group [13]. In 25 women who took green tea extract capsules for 6 months with no control group, fibroid size, symptom scores and laboratory values did not change, while the physical score of a quality of life questionnaire rose [14]. In 16 premenopausal women over 40 given 300 mg of EGCG with vitamin D and vitamin B6 for 90 days, mean fibroid size fell 17.8% and bleeding lasted 0.9 days less, with no change in flow intensity [15].
- Population
- 39 women aged 18 to 50 with symptomatic fibroids, 33 of them analyzed [13]; 25 women, median age 45, with few or no fibroid symptoms [14]; 16 women over 40 with fibroids [15].
- Sources
- [13], [14], [15]
- Caveats
- One small trial, with 11 women finishing on placebo [13]. The hemoglobin and blood loss changes are reported within the green tea group, not as differences from placebo [13]. [14] and [15] had no control group, and [15] combined EGCG with vitamin D and vitamin B6. The trial dose supplies about 360 mg of EGCG a day [13], within the 140 to about 1,000 mg range in liver injury case reports [8].
Pregnancy outcomes
Not shown to lower maternal or newborn death or preterm birth in pregnant women. Night blindness and anemia in mothers were lower.
The numbers and sources
- Effect
- Vitamin A alone did not change maternal death (RR 0.88, 95% CI 0.65 to 1.20), perinatal death (RR 1.01, 95% CI 0.95 to 1.07) or preterm birth (RR 0.98, 95% CI 0.94 to 1.01). Maternal night blindness (RR 0.79, 95% CI 0.64 to 0.98) and maternal anemia (RR 0.64, 95% CI 0.43 to 0.94) were lower [2].
- Population
- 19 trials with over 310,000 women, mostly in Nepal, Ghana and Bangladesh [2].
- Sources
- [2]
- Caveats
- Baseline vitamin A status differed between populations. The reduction in maternal infection (RR 0.45, 95% CI 0.20 to 0.99) came from low quality evidence [2].
Lab markers
Stroke, clots and death in kidney disease trials that raised hemoglobin
Shown in kidney disease trials: aiming for a higher hemoglobin with erythropoietin-type drugs raised stroke, blood pressure and access clotting, and did not lower deaths.
The numbers and sources
- Effect
- In a meta-analysis of 9 trials, a higher hemoglobin target carried a higher risk of death from any cause (risk ratio 1.17, 95% CI 1.01 to 1.35) and of clotting in the dialysis access (1.34, 1.16 to 1.54) than a lower target [12]. A later meta-analysis of 27 trials found that a higher target raised stroke (relative risk 1.51, 95% CI 1.03 to 2.21), hypertension (1.67, 1.31 to 2.12) and access clotting (1.33, 1.16 to 1.53). Differences in death (1.09, 0.99 to 1.20) and serious cardiovascular events (1.15, 0.98 to 1.33) did not reach significance [13].
- Population
- 5,143 patients with anemia from chronic kidney disease in 9 randomized trials [12]. 10,452 patients in 27 trials [13].
- Sources
- [12], [13]
- Caveats
- These trials raised hemoglobin with erythropoiesis-stimulating drugs in people with kidney disease, so they do not show what a higher hemoglobin reached another way does in other people. The second analysis could not separate the effect of the drug dose from the effect of the hemoglobin reached [13].
Heart failure hospital stays in trials of intravenous iron
Shown in trials: intravenous iron cut heart failure hospital stays in iron-deficient patients, possibly more when saturation was below 20%, with no clear effect on deaths.
The numbers and sources
- Effect
- In a meta-analysis of 10 trials, intravenous iron lowered the combined rate of repeat heart failure hospital stays and cardiovascular death (rate ratio 0.75, 95% CI 0.61 to 0.93). Effects on cardiovascular death (odds ratio 0.86, 0.70 to 1.05) and death from any cause (0.93, 0.78 to 1.12) were inconclusive. Patients with a transferrin saturation below 20% had an odds ratio of 0.67 (0.49 to 0.92) for the main outcome, against 0.99 (0.74 to 1.30) at 20% or above (P for difference 0.07) [13]. In pooled patient-level data from 3 trials of one iron product, the rate ratio for cardiovascular hospital stays and cardiovascular death was 0.86 (0.75 to 0.98), with no apparent effect on death. That analysis reported a lower risk of cardiovascular death in the subgroup with saturation below 15% and possibly unfavorable effects at 24% or above [14].
- Population
- 3,373 people with heart failure and iron deficiency in 10 randomized trials [13]. 4,501 people in 3 placebo-controlled trials of ferric carboxymaltose with at least 52 weeks of follow-up [14].
- Sources
- [13], [14]
- Caveats
- The findings by saturation come from subgroup analyses, and the test for a difference between subgroups did not reach significance [13]. The trials enrolled people with heart failure who met a definition of iron deficiency, so they say nothing about iron given to other people with a low saturation.
Death from any cause
Linked to more deaths at both low and high levels in three cohorts of middle-aged and older adults, with the lowest risk in the middle of the range.
The numbers and sources
- Effect
- In 5,888 US adults aged 65 and older followed 11.2 years, the lowest fifth of hemoglobin (below 13.7 g/dL in men, below 12.6 g/dL in women) and the highest fifth had adjusted hazard ratios for death of 1.33 (95% CI 1.15 to 1.54) and 1.17 (1.01 to 1.36) against the fourth fifth. Anemia by WHO criteria had a hazard ratio of 1.38 (1.19 to 1.54) [9]. In 17,030 Canadian adults aged 66 and older, hemoglobin below 11.0 g/dL in people with normal kidney function had a hazard ratio for death of 4.29 (3.55 to 5.12), and risk was lowest at 13.0 to 15.0 g/dL in women and 14.0 to 17.0 g/dL in men [10]. In 292,194 Korean adults over 40, the association with cardiovascular and all-cause death was U-shaped or J-shaped. Men whose anemia had resolved by a second exam had a hazard ratio for death of 0.67 (0.59 to 0.77) against men whose anemia persisted [11].
- Population
- 5,888 community-dwelling adults aged 65 and older in 4 US communities [9]. 17,030 community-dwelling adults aged 66 and older in Calgary, 1,983 deaths over about 3 years [10]. 170,078 men and 122,116 women without cardiovascular disease, median follow-up 8 years [11].
- Sources
- [9], [10], [11]
- Caveats
- Observational. Illness that lowers or raises hemoglobin before death cannot be ruled out, although adjustment for kidney function, inflammation and frailty did not remove the association in the US cohort [9].
Birth outcomes by hemoglobin in pregnancy
Linked to more low birth weight, preterm birth and stillbirth at low maternal hemoglobin, and to more stillbirth at high levels, in pooled studies.
The numbers and sources
- Effect
- In a meta-analysis of 95 studies, low maternal hemoglobin had pooled odds ratios of 1.42 (95% CI 1.31 to 1.55) for low birth weight, 1.36 (1.26 to 1.46) for preterm birth and 1.49 (1.15 to 1.92) for stillbirth. Odds rose as the cutoff fell: for low birth weight, 1.42 at 11.0 g/dL or below and 2.97 (1.85 to 4.75) at 7.0 g/dL or below. High maternal hemoglobin had odds ratios of 1.88 (1.21 to 2.91) for stillbirth and 1.22 (1.08 to 1.37) for a baby small for gestational age, and was not significantly associated with low birth weight or preterm birth [15].
- Population
- 95 studies in the meta-analysis, within a systematic review of 272 [15].
- Sources
- [15]
- Caveats
- Observational. Few studies separated anemia from iron deficiency from other anemia, and results varied with the trimester of measurement. The authors judge the data insufficient to say whether cutoffs need revising [15].
Anemia, low white cell counts and nerve damage at very low levels
Case reports: people with very low serum copper had anemia, low neutrophil counts and nerve damage, most often after stomach or weight loss surgery.
The numbers and sources
- Effect
- A review of records from 1970 to 2005 at one US center identified 40 patients with copper deficiency and blood abnormalities. Ten (25%) had undergone bariatric surgery and 14 (35%) other surgery on the gastrointestinal tract, most often gastric resection. In 12 no cause was identified. Anemia and neutropenia were the most common blood findings, and the majority also had neurologic findings, most commonly myeloneuropathy [11]. A US report describes six patients fed a low-copper enteral diet for 12 to 66 months whose serum copper ranged from 0.9 to 7.2 µmol/L, about 6 to 46 µg/dL. Two had neutropenia, one had anemia and some had reduced bone density, and neutrophil counts normalized after copper was given [3].
- Population
- 40 patients at one US center [11]. Six patients aged 4 to 24 on long-term enteral feeding [3].
- Sources
- [11], [3]
- Caveats
- Case series with no comparison group, drawn from people already found to be deficient. The authors of the review note that copper deficiency is frequently misdiagnosed and may resemble a myelodysplastic syndrome [11]. The µg/dL figures are converted here with the factor on this page.
Anemia and cognitive impairment when folate is high and vitamin B12 is low
Limited evidence: one US survey linked high serum folate together with low B12 status to more anemia and cognitive impairment in older adults.
The numbers and sources
- Effect
- Among seniors with low vitamin B12 status, serum folate above 59 nmol/L (about 26 ng/mL, the 80th percentile) was associated with anemia (OR 3.1, 95% CI 1.5 to 6.6) and cognitive impairment (OR 2.6, 95% CI 1.1 to 6.1), compared with folate at or below that level. Among those with normal B12 status, high folate was associated with less cognitive impairment (OR 0.4, 95% CI 0.2 to 0.9) [15].
- Population
- 1,459 seniors in the 1999 to 2002 US National Health and Nutrition Examination Survey, after folic acid fortification began [15].
- Sources
- [15]
- Caveats
- One cross-sectional survey, so it cannot show cause or order. The ng/mL figure is converted here from the study's nmol/L [15].
Iron deficiency at low values
Limited evidence: in one US survey analysis, MCV told iron-deficient from iron-replete women and children moderately well, and less well than hemoglobin in women.
The numbers and sources
- Effect
- Against iron deficiency defined by body iron stores, the area under the curve for MCV was 0.73 in children aged 3 to 5, 0.80 in nonpregnant women aged 15 to 49 and 0.70 in pregnant women. Hemoglobin scored 0.62, 0.84 and 0.74 in the same groups, and erythrocyte protoporphyrin 0.80, 0.86 and 0.77 [6]. The US recommendations state that a low MCV is a specific sign of iron-deficiency anemia once lead poisoning, the anemias of infection and chronic inflammatory disease, and thalassemia minor are excluded [2].
- Population
- 861 children aged 3 to 5, 3,112 nonpregnant women and 1,150 pregnant women in US national surveys from 1999 to 2006, excluding those with raised lead or C-reactive protein [6].
- Sources
- [6], [2]
- Caveats
- A cross-sectional analysis in US children and women, with iron stores estimated from two blood tests, not from bone marrow. It did not include men [6].
Thalassemia trait at low values
Limited evidence: in one Thai study of pregnant women, an MCV of 80 fL or below picked up 93% of thalassemia trait carriers.
The numbers and sources
- Effect
- An MCV of 80 fL or below had a sensitivity of 92.9% and a specificity of 83.9% for alpha-thalassemia-1 and beta-thalassemia traits. The positive predictive value was 37.9% and the negative predictive value 99.1% [7].
- Population
- 439 pregnant women at one antenatal clinic in Chiang Mai, Thailand, each tested by hemoglobin analysis and gene testing [7].
- Sources
- [7]
- Caveats
- One clinic in a region where thalassemia traits are common, so the predictive values do not carry over to places where they are rare. About 6 in 10 women with a low MCV did not carry either trait [7].
Anemia and enlarged red cells
Limited evidence: one US survey linked low B12 status to 2.7 times the odds of anemia in older adults.
The numbers and sources
- Effect
- Low compared with normal B12 status was associated with anemia (OR 2.7, 95% CI 1.7 to 4.2) and macrocytosis (OR 1.8, 95% CI 1.01 to 3.3), after control for demographic characteristics, cancer, smoking, alcohol intake, serum ferritin and serum creatinine. Low status was defined as serum B12 below 148 pmol/L (about 200 pg/mL) or methylmalonic acid above 210 nmol/L [7].
- Population
- 1,459 seniors with normal serum creatinine and no history of stroke, alcoholism, recent anemia therapy, or liver, thyroid or coronary disease [7].
- Sources
- [7]
- Caveats
- One cross-sectional survey, so it cannot show which came first. The definition of low status combined two tests [7].
Vitamin B12 deficiency at high values
Mixed results: a raised MCV picked up 17% to 77% of vitamin B12 deficiency depending on the group studied, so many deficient people had an MCV that was not raised.
The numbers and sources
- Effect
- In a systematic review, the sensitivity of a raised MCV for B12 deficiency was 17% in people screened at random and 30% in screened people with anemia. Where B12 was measured as part of care, sensitivity was 30% for a low serum B12, 58% for confirmed deficiency and 75% for deficiency with anemia. In pernicious anemia it was 77%. The positive predictive value ranged from 0% to 55% in the 5 studies reporting it. The authors calculate that up to 84% of cases would be missed if a raised MCV were the only reason to test [8].
- Population
- 37 original studies of anemic and non-anemic patients [8].
- Sources
- [8]
- Caveats
- Studies used different cut points for both MCV and serum B12, and results were pooled without taking these into account [8].
Death and heart attack in a dialysis trial that raised hematocrit to 42%
One trial found raising hematocrit to 42% with epoetin did not cut deaths or heart attacks in hemodialysis patients with heart disease, and the trial was halted.
The numbers and sources
- Effect
- Patients were assigned to epoetin doses aimed at a hematocrit of 42% or of 30%. After 29 months there were 183 deaths and 19 first nonfatal heart attacks in the 42% group and 150 deaths and 14 nonfatal heart attacks in the 30% group, a risk ratio of 1.3 (95% CI 0.9 to 1.9). The difference did not reach the preset stopping boundary, and the study was halted. Within each group, death rates fell as the hematocrit reached rose [11].
- Population
- 1,233 people on hemodialysis with heart failure or ischemic heart disease, treated for a median of 14 months [11].
- Sources
- [11]
- Caveats
- One trial in people on dialysis with heart disease, in whom hematocrit was raised with a drug. The higher target group also had a decline in the adequacy of dialysis and more intravenous iron, so the trial cannot separate hematocrit from the treatment used to raise it [11].
- Why limited
- This rests on one trial, of 1,233 people. Strength counts independent studies that agree, so one trial is limited at any size.