Quick answer
Adults need 30 mcg of biotin a day, and 35 mcg while breastfeeding, counting food and supplements together. Most diets already supply that much. Supplements often hold far more, such as 10,000 mcg, and no amount has been shown to change hair in people who get enough.1,2,3
Key facts
- On supplement labels the Daily Value for biotin is 30 mcg, so 300 mcg is 10 times the Daily Value and 10,000 mcg is about 333 times.1
- The small nail studies used 2.5 mg (2,500 mcg) a day for several months.1
- Experts could not set an upper limit for biotin, because no toxic effect has been found in people.1,4
- Intakes above the recommended amount can make some lab tests give wrong results.5
How much biotin you need by age
| Life stage | Biotin per day |
|---|---|
| Birth to 6 months | 5 mcg |
| 7 to 12 months | 6 mcg |
| 1 to 3 years | 8 mcg |
| 4 to 8 years | 12 mcg |
| 9 to 13 years | 20 mcg |
| 14 to 18 years | 25 mcg |
| Adults 19 and older | 30 mcg |
| Pregnancy | 30 mcg |
| Breastfeeding | 35 mcg |
These figures are adequate intakes, not recommended dietary allowances. The data were too thin for a firmer number, so experts started from the biotin infants get in breast milk and scaled it up by body weight for older groups.1
The adult amount is the same for men and women and does not change after 19, so a man, a woman over 50 and a woman over 60 all need 30 mcg a day.1
Reading the label: micrograms and percent Daily Value
The Daily Value for biotin is 30 mcg, so a 5,000 mcg supplement provides about 167 times the Daily Value.1
| Amount on the label | Same amount in mg | Times the Daily Value |
|---|---|---|
| 30 mcg | 0.03 mg | 1 |
| 300 mcg | 0.3 mg | 10 |
| 1,000 mcg | 1 mg | about 33 |
| 5,000 mcg | 5 mg | about 167 |
| 10,000 mcg | 10 mg | about 333 |
Labels switch between units, and 1 mg equals 1,000 mcg. A product listing 10 mg of biotin per serving is the same as one listing 10,000 mcg.2
Amounts used in studies
The small nail studies that NIH describes used 2.5 mg (2,500 mcg) of biotin a day for several months.1
A study of lab test errors in healthy adults used 10 mg (10,000 mcg) a day, which its authors describe as a dose common in over-the-counter supplements.2
For hair, the only reports used 3 to 5 mg a day in a few children with a rare inherited hair problem. No study in our sources set a dose for hair growth in healthy adults, and a review of the published cases found too little evidence to recommend biotin to people without an underlying cause.1,3
Why more is not better
Food alone usually provides 35 to 70 mcg a day, above the adult need, so for most people a supplement adds biotin beyond what the body is known to need.1,7
At the recommended 30 mcg a day, biotin in the blood stays below 1 ng/mL. Supplements can push it above that, and intakes of up to 300 mg a day, which some people take, raise it above 1,000 ng/mL.5
Those higher blood levels are what upset lab tests. In a small study, healthy adults taking 10 mg a day for one week already had wrong results on some tests that use biotin.2
What's in ours
What’s in ours
- Men's Multi: Biotin, 300 mcg per serving, from the label
Before you take a high dose
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
- Tell your doctor and the lab that you take biotin, and how much, before any blood test5
- Ask first if you take levothyroxine or another thyroid medicine, whose dose is set by blood tests8
- Ask first if you are pregnant or breastfeeding
- Add up the biotin in every product you take, including a multivitamin or B complex6
Questions people ask
How much biotin per day for hair growth?
No amount has been shown to grow hair in people who get enough biotin. The case reports that exist used 3 to 5 mg a day in children with a rare inherited hair problem, and NIH says more research is needed, especially in healthy people.1,3
How much biotin per day for a woman?
Women need 30 mcg a day, the same as men, including during pregnancy. While breastfeeding the amount rises to 35 mcg.1
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Sources
- National Institutes of Health, Office of Dietary Supplements. Biotin: Fact Sheet for Health Professionals. Updated January 10, 2022. Opened 2026-10-07.
- Li D, Radulescu A, Shrestha RT, et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA. 2017;318(12):1150-1160. Opened 2026-10-07.
- Patel DP, Swink SM, Castelo-Soccio L. A Review of the Use of Biotin for Hair Loss. Skin Appendage Disord. 2017;3(3):166-169. Opened 2026-10-07.
- 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.
- U.S. Food and Drug Administration. Testing for Biotin Interference in In Vitro Diagnostic Devices: Guidance for Industry. October 2020. Opened 2026-10-07.
- National Institutes of Health, Office of Dietary Supplements. Biotin: Fact Sheet for Consumers. Updated January 15, 2021. Opened 2026-10-07.
- Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Summary. Washington, DC: National Academies Press; 1998. doi:10.17226/6015. Opened 2026-10-07.
- Levothyroxine sodium tablets: prescribing information (Cardinal Health 107, LLC). DailyMed, U.S. National Library of Medicine. Published September 24, 2026. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.