Quick answer

NIH sets the adequate intake of biotin while breastfeeding at 35 mcg a day, 5 mcg above the amount for other adults, and has set no upper limit. It notes that biotin in breast milk and blood falls during breastfeeding. No source checked measured the effect of high-dose biotin on nursing infants.^1,2

Key facts

The adequate intake of biotin while breastfeeding is 35 mcg a day, against 30 mcg for other adults.^1,2
NIH says biotin in blood and breast milk falls during breastfeeding even when intake is above the adequate intake, and that what this means for health is not yet known.¹
NIH names pregnant and breastfeeding women among the groups more likely to run low on biotin.²
No upper limit is set, because there is no evidence in humans that biotin is toxic, but extra biotin can make some blood tests read falsely high or low.^1,3

What NIH says about biotin while nursing

NIH derived its adequate intakes from the amount of biotin in the human milk that infants consume, extrapolated by body weight to other groups, and it gives a higher figure for breastfeeding women. It states the figure as an adequate intake, not a recommended allowance, because there was too little evidence to set an allowance.¹

Adults need 30 mcg of biotin a day, the same amount during pregnancy, and 35 mcg while breastfeeding. These are adequate intakes, set because there was not enough evidence for a recommended dietary allowance.^1,2

At least a third of pregnant women develop marginally low biotin status despite normal intakes, and biotin in blood and breast milk falls during breastfeeding even when intake is above the adequate intake. What this means for health is not yet known.¹

Between them the two entries show that the need is higher while nursing and that levels fall during nursing. They do not say that a supplement changes the amount reaching the baby.^1,2

What is not known about high-dose biotin and breast milk

The sources checked for this page do not report how much of a high-dose biotin supplement passes into breast milk, or whether it affects a nursing infant. The NIH sheets describe studies of 10 to 50 mg a day in adults and people with a rare inherited biotin condition taking up to 200 mg a day, none in breastfeeding women.¹

That is not a finding of harm and it is not a finding of no harm. It is a gap. The upper limit entry from the biotin file shows how NIH describes it.¹

No upper limit has been set for biotin, because there is no evidence in humans that it is toxic at high intakes. Studies giving 10 to 50 mg a day found no adverse effects, and people with a rare inherited condition that affects biotin have taken up to 200 mg a day by mouth without signs of toxicity. The main known risk of high intakes is wrong lab test results.^1,4

Can biotin affect a nursing mother's blood tests?

Yes, this is the documented concern. A blood sample that contains extra biotin can give a falsely high or falsely low result on tests built with biotin, including thyroid and some hormone tests.^1,3

Even a single 10 mg dose of biotin has interfered with thyroid function tests done within the following 24 hours.¹

A nursing mother who takes biotin and has a postpartum thyroid test or other blood work is among the people who should ask her doctor whether the supplement could affect the result. The same goes for thyroid medicine doses that are adjusted from those tests.^1,5

Who should ask a doctor before taking biotin while nursing

Breastfeeding women thinking about a biotin product with more than the 35 mcg intake, who should ask their doctor or pharmacist.²
Women whose baby was born early or has a medical condition, who should ask the baby's doctor before any supplement.
Women taking levothyroxine, anticonvulsant medicines or other prescriptions, who should ask their pharmacist about biotin.¹

NIH notes that biotin supplements are often promoted for hair, skin and nails, and gives a 5,000 mcg product as an example that provides about 167 times the Daily Value. The panel is worth reading before any product is started.¹

Questions people ask

Is a biotin supplement safe while breastfeeding?

NIH has set no upper limit for biotin and its sheets describe no studies in breastfeeding women at high doses. That is a gap in the evidence, so ask your doctor or pharmacist about a specific product.¹

Is biotin shampoo safe while breastfeeding?

The sources on this page cover biotin taken by mouth. They do not address shampoos or other hair and skin products, which is not a finding either way. Ask your pharmacist.²

Is biotin tablet okay during breastfeeding?

NIH sets the adequate intake at 35 mcg a day while breastfeeding. A tablet's amount is on its label, and NIH's own example is a 5,000 mcg supplement, about 167 times the 30 mcg Daily Value. The effect of such amounts on breast milk was not reported in the sources checked. Ask your doctor.^1,2

Do breastfeeding women need more biotin?

NIH's adequate intake is 35 mcg a day while breastfeeding, against 30 mcg for other adults, and NIH says biotin levels in milk fall during breastfeeding even above that intake.^1,2

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This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.