Is niacin safe during pregnancy?

Niacin from food, yes. According to the NIH Office of Dietary Supplements, no adverse effects have been reported from niacin that occurs naturally in food. Supplements are a different question, and nobody has answered it in pregnancy. We found no randomized trial of niacin supplements in pregnant women. In other adults, 30 to 50 mg or more of nicotinic acid typically causes flushing, and niacin taken as a cholesterol drug was linked to a 34 percent higher risk of new diabetes (risk ratio 1.34, 95% CI 1.21 to 1.49).

For food, the agency position is the whole evidence, and it is reassuring: no reported harm. The upper limit set in the United States, 35 mg a day, applies only to niacin from supplements and medicines.

Unsettled. Whether a niacin supplement does anything for a pregnancy is untested. The pregnancy evidence is observational, it links low niacin intake with more birth defects and gestational diabetes, and diet recall studies like these cannot separate niacin from the overall quality of a woman's diet.

The two niacin numbers that come with a confidence interval

Randomized trialsObservational data

Right of 1.0 means more of the outcome. The top row is an odds ratio from case-control studies that asked mothers to recall their diet, so it shows an association, not an effect. The bottom row is a risk ratio from trials of niacin as a cholesterol drug in adults who were not pregnant. Neither abstract gives absolute numbers. Sources: cards ev-nipg-01 and ev-nipg-04 below.

What the trials found

There are no trials in pregnancy, so this section reports what the closest studies found and how far each one is from the question.

Low intake and birth defects

A 2022 meta-analysis of case-control studies found that mothers with insufficient niacin intake were more likely to have babies with congenital abnormalities (odds ratio 1.13, 95% CI 1.02 to 1.24). These studies asked mothers to remember what they ate, and the effect is small. It is an odds ratio from observational data, so it is a link, and a diet low in niacin is usually low in other things too.

Low intake and gestational diabetes

In a Korean cohort of pregnant women, insufficient niacin intake was linked to a higher risk of gestational diabetes (risk ratio 1.54). The abstract gives no confidence interval for that figure, and intake was measured with a single 24-hour diet recall. In the same study vitamin D, vitamin K and vitamin B6 showed similar or larger links, which points to diet quality as a whole.

Miscarriage

The idea that vitamin B3 prevents miscarriage comes from work in mice. In people it has not held up so far. In a pilot of 24 women under 14 weeks pregnant, neither niacin intake (P = 0.24) nor a urine marker of vitamin B3 (P = 1.00) predicted miscarriage. An Australian pilot of 88 women who were not pregnant at the time found that higher blood levels of a niacin breakdown product went with a history of recurrent miscarriage (adjusted odds ratio 1.02 per unit, 95% CI 1.01 to 1.03). That is a blood marker, not a test of a supplement, and we found no trial of vitamin B3 to prevent miscarriage in humans.

After birth

The one randomized trial near this question was in breastfeeding mothers, not pregnant ones. Women in rural Tanzania took 250 mg of nicotinamide a day or a placebo from the first two weeks after birth until six months. On nicotinamide, vitamin B3 in breast milk was 291 percent higher than on placebo at one month, and 72.9 percent of women had levels above the upper reference limit. That dose is about seven times the US upper limit, given inside a supervised study.

Who should be careful

Not for everyone. High-dose niacin is a medicine, and in pregnancy it belongs with a doctor. In a meta-analysis of trials in adults without diabetes, niacin given at cholesterol-lowering doses was linked to a 34 percent higher risk of new diabetes (risk ratio 1.34, 95% CI 1.21 to 1.49). Those adults were not pregnant, and the abstract gives no absolute numbers. Pregnancy already carries a risk of gestational diabetes.

Flushing is the usual first side effect. According to NIH, 30 to 50 mg or more of nicotinic acid typically turns the skin of the face, arms and chest red. The upper limit is based on that flushing and covers both forms, nicotinic acid and nicotinamide. It does not apply to people taking niacin under medical supervision.

If you take simvastatin, the FDA label reports cases of muscle damage, including rhabdomyolysis, when it is combined with niacin at 1 gram a day or more.

The one report of treatment-dose niacin in pregnancy is a single woman with very high triglycerides, above 3,000 mg/dL. Under specialist care her niacin was raised to 2,000 mg a day, which kept triglycerides below 1,000 mg/dL for the rest of the pregnancy. The report notes that her children had developmental problems, with no cause established. One case cannot show that the dose was safe or that it caused harm.

What expert bodies say

The NIH Office of Dietary Supplements says no adverse effects have been reported from niacin in food, and that the upper limit applies only to supplemental niacin. The US upper limit for nicotinic acid is 35 mg a day and the European one is 10 mg. A 2017 dose-response review argued that both limits may be highly conservative. That review mixed trials with observational studies and did not look at pregnant women. We found no statement on niacin supplements in pregnancy from NIH or from the American College of Obstetricians and Gynecologists.

How we searched

Searched: a local copy of PubMed for niacin, nicotinamide, nicotinic acid or vitamin B3 with pregnancy, birth defects, miscarriage and pre-eclampsia (100 hits), for NAD deficiency (3 hits), for niacin with diabetes and side effects in meta-analyses (14 hits), for niacin with gestational diabetes or pre-eclampsia (10 hits), and for multiple micronutrients in pregnancy (28 hits). The NIH Office of Dietary Supplements, a local layer of agency documents, the LactMed database, drug label interactions, a web search for newer studies, and a retraction check, which found none of the sources retracted. Search run on 7 October 2026.

Included: one meta-analysis of randomized trials, one randomized trial, two further meta-analyses of observational or mixed studies, three cohorts, one case report, two NIH passages and one FDA label, cited below as eleven cards.

Excluded: a cohort in which niacin intake was higher in the women who developed gestational diabetes, the opposite direction to the Korean study, because its abstract gave no effect size for niacin. We note it here because it conflicts. Trials of multiple micronutrient tablets, where niacin is one ingredient among many. Two further case reports of niacin for pancreatitis in pregnancy, and case reports of genetic diseases in children.

What we read: abstracts, and the relevant sections of the NIH fact sheet and the FDA label, each quotation checked against the source.

What we could not get: the 2017 New England Journal of Medicine study of NAD deficiency in four families and niacin in mice, which is not in our copy of PubMed and has no free full text. LactMed has no niacin monograph, which is not evidence of safety. The pregnancy recommended intake sits in an NIH table we could not quote.

What would change this answer

A randomized trial of niacin or nicotinamide at ordinary supplement doses in pregnant women. None has been run that we could find.
A prospective study of birth defects that measures niacin status in blood before or around conception, instead of asking mothers to recall their diet afterward.
A human trial of vitamin B3 in women with recurrent miscarriage. The idea comes from mice and from blood markers, and nobody has tested it.
Follow-up of the children in the Tanzanian breastfeeding trial, reported in a form we can check.

How much niacin you need and which foods carry it is in the niacin guide.

The rest of the nutrient, in one place. Niacin: the vitamin that became a heart drug and then failed the trials → What it does, how much you need, who runs short, and what too much does, with the evidence level shown on every line.

The full guide

Niacin: the vitamin that became a heart drug and then failed the trials

The same question for other foods (pregnancy)

Sources

ev-nipg-01 · Observational data · systematic review and meta-analysis of case-control studies · n = 35743
The meta-analysis showed that expectant mothers with an insufficient niacin intake were significantly more likely to have babies with congenital abnormalities (odds ratio 1.13, 95% confidence interval 1.02-1.24) compared to mothers with adequate niacin intake.
Who: mothers of babies with and without congenital anomalies; periconceptional dietary niacin intake; US, Netherlands, South Africa
Effect: insufficient vs adequate niacin intake: congenital anomalies OR 1.13 (95% CI 1.02 to 1.24); OR 1.15 (1.03 to 1.26) in quality sensitivity analysis
Certainty: Case-control only, intake from recall; OR is odds; the effect is small, residual confounding by diet quality.
Eur J Nutr, 2022 · checked 2026-10-07 · we read the abstract
ev-nipg-02 · Observational data · prospective cohort · n = 2227
Among individual nutrients, inadequate vitamin D intake was associated with the highest GDM risk (RR = 3.84), followed by insufficient intakes of vitamin K (RR = 1.89), vitamin B6 (RR = 1.62), niacin (RR = 1.54), and calcium (RR = 1.39).
Who: Korean singleton pregnancies; 24-hour dietary recall in early pregnancy; OGTT at 24 to 28 weeks
Effect: insufficient niacin intake RR 1.54 for GDM; lowest vs highest overall adequacy quartile OR 1.82 (1.10 to 2.99)
Certainty: A single 24-hour recall; no CI for niacin in the abstract; niacin is a marker of overall diet quality.
Nutrients, 2025 · checked 2026-10-07 · we read the abstract
ev-nipg-03 · Randomized controlled trial(s) · secondary analysis of a randomized placebo-controlled trial · n = 1173
Maternal nicotinamide supplementation was associated with many participants having human-milk total vitamin B-3 concentrations exceeding the upper reference limit (72.9% ≥3.284 mg/L at 1 mo; 50.7% ≥2.760 mg/L at 5 mo), and a sustained higher median concentration with supplementation compared with placebo (by 291% at month 1 and 281% at month 5).
Who: lactating women in rural Haydom, Tanzania, randomized to nicotinamide 250 mg/day or placebo from infant age under 2 weeks to 6 months
Effect: milk total B3 above upper reference limit in 72.9% at 1 month; median +291% vs placebo at month 1 and +281% at month 5; no association with child growth or MDAT scores at 18 months
Certainty: Breastfeeding, not pregnancy; 250 mg of nicotinamide is 7 times above the UL of 35 mg, but under the supervision of the study.
Am J Clin Nutr, 2026 · checked 2026-10-07 · we read the abstract
ev-nipg-04 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials · n = 26340
Niacin therapy was associated with a RR of 1.34 (95% CIs 1.21 to 1.49) for new-onset diabetes, with limited heterogeneity between trials (I(2)=0.0%, p=0.87).
Who: non-diabetic adults in cardiovascular RCTs of niacin therapy (not pregnant)
Effect: new-onset diabetes RR 1.34 (95% CI 1.21 to 1.49); one extra case per 43 people treated for 5 years
Certainty: Therapeutic doses of 1-2 g/day in non-pregnant people; important for pregnant women because of GDM risk, no direct data.
Heart, 2016 · checked 2026-10-07 · we read the abstract
ev-nipg-05 · Observational data · systematic review and dose-response meta-analysis of trials and observational studies · n = 11741
Conclusions: Results may indicate a high degree of conservativeness in the UL of nicotinic acid, fixed at 35 mg/d in United States and 10 mg/d in Europe.
Who: people taking nicotinic acid or nicotinamide supplements in trials and observational studies
Effect: healthy individuals: major adverse effects below 1000 mg/day nicotinic acid; UL 35 mg/day US vs 10 mg/day Europe
Certainty: Mixed designs, hence C; pregnant women not singled out; discrepancy between the US UL (35) and EU UL (10) for nicotinic acid.
Nutr Rev, 2017 · checked 2026-10-07 · we read the abstract
ev-nipg-06 · Position of an expert body · government fact sheet · n = —
No adverse effects have been reported from the consumption of naturally occurring niacin in foods [2]. However, high intakes of both nicotinic acid and nicotinamide taken as a dietary supplement or medication can cause adverse effects, although their toxicity profiles are not the same. Thirty to 50 mg or more nicotinic acid typically causes flushing; the skin on the patient’s face, arms, and chest turns a reddish color because of vasodilation of small subcutaneous blood vessels.
Who: general population; supplement and medication users
Effect: no adverse effects from food niacin; flushing from 30-50 mg nicotinic acid
Certainty: Key to the question "is it safe?": food yes, supplements above the UL no without a doctor.
NIH Office of Dietary Supplements, Niacin Fact Sheet for Health Professionals · checked 2026-10-07 · we read the section
ev-nipg-07 · Position of an expert body · government fact sheet · n = —
The FNB has established ULs for niacin that apply only to supplemental niacin for healthy infants, children, and adults [2]. These ULs are based on the levels associated with skin flushing. The FNB acknowledges that although excess nicotinamide does not cause flushing, a UL for nicotinic acid based on flushing can prevent the potential adverse effects of nicotinamide [2]. The UL, therefore, applies to both forms of supplemental niacin. However, the UL does not apply to individuals who are receiving supplemental niacin under medical supervision [2].
Who: healthy infants, children and adults taking supplemental niacin
Effect: UL based on flushing; covers nicotinic acid and nicotinamide; excludes medically supervised treatment
Certainty: There is no separate UL for pregnant women in this excerpt; the ODS table (35 mg for adults, including pregnant) is not a quote.
NIH Office of Dietary Supplements, Niacin Fact Sheet for Health Professionals · checked 2026-10-07 · we read the section
ev-nipg-08 · Position of an expert body · FDA-approved drug label · n = —
Niacin Clinical Impact: Cases of myopathy and rhabdomyolysis have been observed with concomitant use of lipid modifying dosages of niacin-containing products (≥1 gram/day niacin) with simvastatin.
Who: patients taking simvastatin with niacin-containing products
Effect: myopathy and rhabdomyolysis with niacin at 1 g/day or more plus simvastatin
Certainty: Interaction of therapeutic doses; statins are usually not used in pregnancy, but this is about supplements and drugs, not food.
Simvastatin tablets, FDA-approved label (DailyMed), effective 2026-02-26 · checked 2026-10-07 · we read the section
ev-nipg-09 · Laboratory or animal data · case report · n = 1
Due to persistent hypertriglyceridemia (>3000 mg/dL, 33.9 mmol/L), niacin was added as an additional therapy and titrated to 2000 mg/day, which successfully sustained TG levels below 1000 mg/dL (11.3 mmol/L) through the remainder of her pregnancy.
Who: one 29-year-old woman with recurrent severe hypertriglyceridemia in two pregnancies
Effect: niacin titrated to 2000 mg/day kept TG below 1000 mg/dL; delivery at 35 weeks for preeclampsia
Certainty: A single case, therapeutic dose under supervision; the children had developmental disorders, cause not established.
Case Rep Endocrinol, 2025 · checked 2026-10-07 · we read the abstract
ev-nipg-10 · Observational data · prospective pilot cohort · n = 24
Neither niacin intake (P = 0.24) nor urinary vitamin B3 measured as the 1-methyl-5-carboxylamide-2-pyridone/N-1-methylnicotinamide (2-pyr/MNA) ratio (P = 1.00) predicted miscarriage.
Who: women less than 14 weeks pregnant
Effect: niacin intake P = 0.24; urinary 2-pyr/MNA ratio P = 1.00 for miscarriage
Certainty: Very small study; the answer to the mouse hypothesis (vitamin B3 against miscarriages) has not been confirmed in humans.
Aust N Z J Obstet Gynaecol, 2021 · checked 2026-10-07 · we read the abstract
ev-nipg-11 · Observational data · prospective pilot cohort (cross-sectional comparison) · n = 88
1MNA in plasma was associated with recurrent miscarriage on univariate analysis, with the effect sustained after taking into account maternal age (adjusted odds ratio 1.02; 95% CI 1.01, 1.03) with every one-unit increase in 1MNA, the odds of miscarriage increasing by 2%.
Who: non-pregnant women aged 20 to 40 in Sydney, 37 with and 51 without recurrent miscarriage
Effect: plasma 1MNA adjusted OR 1.02 (95% CI 1.01 to 1.03) per unit; three-metabolite model AUROC 0.89
Certainty: Biomarkers, not an intervention; no RCT of vitamin B3 for preventing miscarriage in humans was found.
Hum Reprod, 2025 · checked 2026-10-07 · we read the abstract

How this page was made. Evidence was extracted from primary sources into cards, every number was re-checked against the source, and the text was written from those cards. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.