Is B complex safe while breastfeeding?

How much of each B vitamin does NIH give while breastfeeding?

NIH sets higher amounts for most B vitamins while breastfeeding. The table gives them for women 19 and older, with the adult upper limits that also apply while nursing.^2,4,6

These are amounts from all sources, food and supplements together. They are not amounts to buy, and none of the sources describes a B complex product at these figures. For vitamin B6, NIH notes that Europe's food safety authority set a lower upper limit of 12 mg a day in 2023, for all adults including women who are lactating.^1,2

What studies show about B vitamins and breast milk

Trials mostly measure how much of a vitamin reaches the milk, not harm. In one, mothers took 2 mg or 27 mg of pyridoxine a day in the first 28 days of breastfeeding. The vitamin B6 in the milk, and the infants' intake, followed the amount in the mother's supplement.⁷

In another trial, 183 women took 50 mcg of vitamin B12 a day from early pregnancy to 6 weeks after delivery and 183 took placebo. Milk B12 at 6 weeks was higher in the supplemented group, with a median of 136 pmol/L against 87.⁸

These show that the vitamins move into milk. They do not show whether any amount is too much for an infant, and the trials did not set out to look for that.

What the Cochrane review could not say

A Cochrane review looked for trials of supplements with three or more micronutrients, the group a B complex belongs to, in breastfeeding women. It found two small studies, 52 women in all, with no usable numbers on the harms it was looking for.³

Its authors wrote that there is no evidence to evaluate the potential adverse effects of multiple-micronutrient supplements, particularly excess dosages. That sentence is the honest summary for B complex while nursing: the gap is real, and it is not a finding of harm either.³

People who eat no animal foods get no natural vitamin B12 and need fortified foods or supplements. Vegans and people who eat little dairy are also more likely to fall short of riboflavin.^1,13

Who should ask a doctor about B complex while nursing

• Mothers who eat no animal foods, who should ask their doctor about vitamin B12. NIH says exclusively breastfed infants of mothers who eat no animal products can develop B12 deficiency, sometimes very early.¹
• Mothers who take a prenatal vitamin and a B complex together, who should ask their pharmacist to add up the vitamin B6, niacin and folic acid against the upper limits.^2,4,6
• Mothers taking levothyroxine, an anticonvulsant, methotrexate or metformin, or having blood work, because biotin and some B vitamins interact.^4,5,14

Questions people ask

Sources

1. National Institutes of Health, Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. Updated July 2, 2025. Opened 2026-10-07.
2. National Institutes of Health, Office of Dietary Supplements. Vitamin B6: Fact Sheet for Health Professionals. Updated June 16, 2023. Opened 2026-10-07.
3. Abe SK, Balogun OO, Ota E, Takahashi K, Mori R. Supplementation with multiple micronutrients for breastfeeding women for improving outcomes for the mother and baby. Cochrane Database Syst Rev. 2016;2:CD010647. A Cochrane systematic review of randomized trials. Opened 2026-10-11.
4. National Institutes of Health, Office of Dietary Supplements. Folate: Fact Sheet for Health Professionals. Updated November 30, 2022. Opened 2026-10-07.
5. National Institutes of Health, Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals. Updated January 10, 2022. Opened 2026-10-07.
6. National Institutes of Health, Office of Dietary Supplements. Niacin: Fact Sheet for Health Professionals. Updated November 18, 2022. Opened 2026-10-07.
7. Kang-Yoon SA, Kirksey A, Giacoia G, West K. Vitamin B-6 status of breast-fed neonates: influence of pyridoxine supplementation on mothers and neonates. Am J Clin Nutr. 1992;56(3):548-58. A randomized trial in breastfeeding mothers. Opened 2026-10-11.
8. Duggan C, Srinivasan K, Thomas T, Samuel T, Rajendran R, Muthayya S, et al. Vitamin B-12 supplementation during pregnancy and early lactation increases maternal, breast milk, and infant measures of vitamin B-12 status. J Nutr. 2014;144(5):758-64. A randomized, placebo-controlled trial. Opened 2026-10-11.
9. National Institutes of Health, Office of Dietary Supplements. Thiamin: Fact Sheet for Health Professionals. Updated February 9, 2023. Opened 2026-10-07.
10. National Institutes of Health, Office of Dietary Supplements. Riboflavin: Fact Sheet for Health Professionals. Updated May 11, 2022. Opened 2026-10-07.
11. Institute of Medicine. Pantothenic Acid. In: Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998. Chapter 10. doi:10.17226/6015. Opened 2026-10-07.
12. National Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium. Appendix J: Dietary Reference Intakes Summary Tables. Washington, DC: The National Academies Press; 2019. doi:10.17226/25353. Opened 2026-10-07.
13. National Institutes of Health, Office of Dietary Supplements. Riboflavin: Fact Sheet for Consumers. Updated May 11, 2022. Opened 2026-10-07.
14. Levothyroxine sodium tablets: prescribing information (Cardinal Health 107, LLC). DailyMed, U.S. National Library of Medicine. Published September 24, 2026. Opened 2026-10-07.