What is biotin?
Biotin, also known as vitamin B7 or vitamin H, is a water-soluble B-complex vitamin that helps the body convert food into energy. It is an essential nutrient that plays a key role in the health of hair, skin and nails. Biotin is present in many foods and available as an oral supplement.
Biotin and hair growth
Biotin is often associated with hair growth and healthier hair. That’s because this vitamin helps produce keratin, a protein that makes up your hair, skin and nails. Keratin is the structural protein that makes up around 90% of your hair.
Biotin is also required for the production of fatty acids. These fatty acids are incorporated into the cellular membrane of the hair follicle, which appear to play a role in hair growth and retention.
Sufficient biotin intake can help with hair growth in the following ways:
- May help produce keratin which is needed for healthy hair
- May increase hair growth rate
- May increase hair elasticity, making it less prone to damage and breakage
- May help thicken hair fibers
For these reasons, biotin supplements are commonly marketed for hair, skin and nail benefits. Many people take biotin supplements in hopes it will make their hair grow faster, longer and healthier.
Biotin deficiency and hair loss
Biotin deficiency is rare but can cause hair thinning and loss in severe cases. Risk factors for biotin deficiency include:
- Pregnancy
- Long-term use of certain anti-seizure medications
- Prolonged antibiotic use
- Intestinal malabsorption disorders
- Alcoholism
Deficiency can also occur with severe malnutrition or eating lots of raw egg whites, which contain a protein (avidin) that binds to biotin and prevents its absorption.
Symptoms of biotin deficiency include:
- Thin, brittle hair
- Hair loss
- Dry, flaky skin
- Cracking in the corners of the mouth
How much biotin per day for hair growth?
The recommended dietary allowance (RDA) for biotin is:
- 30 mcg per day for adults
- 35 mcg during pregnancy
- 45 mcg while breastfeeding
This is the amount needed to prevent deficiency. However, many experts believe up to 100–300 mcg of biotin per day may be optimal for supporting hair growth and overall health.
Here is a more detailed look at the research on biotin dosage for hair growth:
Studies on Biotin Dosage
100–300 mcg per day
Several studies have used biotin dosages in the range of 100–300 mcg per day and reported benefits for hair:
– A 90-day study in women with thinning hair found that supplementing with 100 mcg of biotin per day significantly increased hair volume and improved nail hardness and thickness (1).
– A double-blind placebo controlled study in women with temporary hair shedding found that those who took 300 mcg of biotin per day had significant improvement in hair growth after 90 and 180 days (2).
– A study in persons with brittle nails found that 2.5 mg per day of biotin for 6 to 15 months increased nail thickness by 25% (3).
2,500–5,000 mcg per day
Some studies have used very high doses of 2,500–5,000 mcg per day:
– A study in women complaining of hair loss found that 5,000 mcg of biotin per day, for 90 to 180 days, significantly increased hair growth compared to placebo (4).
– However, another study did not find a significant benefit on hair growth from 2,500 mcg of biotin per day in women with female pattern hair loss (5).
– High biotin doses may improve brittle nails. One study found 2.5 mg per day increased nail thickness by 25% over 6 to 15 months (3).
10,000–30,000 mcg per day
A few studies have given extremely high doses of 10,000–30,000 mcg per day:
– A study in patients with progressive multiple sclerosis found 300 mg (30,000 mcg) of biotin per day improved hair and skin (6).
– Case studies suggest 20 mg (20,000 mcg) per day may help with certain inborn errors of metabolism, but data are lacking (7).
Is more better for hair growth?
Overall, the research suggests:
– Doses of around 100–300 mcg per day are sufficient for preventing biotin deficiency.
– Doses of 1,000–5,000 mcg may provide added benefit for hair, skin and nails. However, not all studies agree.
– Doses above 5,000 mcg have not been well studied for hair growth. Very high doses may not provide further benefit and are more likely to cause side effects.
For optimal hair growth, aim for 100–300 mcg of biotin per day or up to 5,000 mcg if you want to try a higher dose. Work with your healthcare provider to find the right dosage for your individual needs.
Top biotin-rich foods
In addition to supplements, you can get biotin from certain foods:
| Food | Biotin per 3 oz (85g) serving |
|---|---|
| Beef or pork liver | 30–35 mcg |
| Egg yolks | 10 mcg |
| Salmon | 5 mcg |
| Cheese | 0.4–2 mcg |
| Almonds | 1.5 mcg |
| Sweet potato, cooked | 2–4 mcg |
| Avocado | 2–6 mcg |
| Raspberries | 0.5 mcg |
Getting 30–35 mcg biotin from food sources per day should meet the RDA and prevent deficiency in most people.
Those wanting a higher intake for hair growth may get an additional 50–100 mcg naturally through foods like:
– 1 whole egg plus 2 egg yolks (25 mcg)
– 3 oz salmon (5 mcg)
– 1 oz almonds (1.5 mcg)
– 1 avocado (6 mcg)
– 3 oz cheese (1.2 mcg)
However, it can be difficult to get hundreds or thousands of micrograms per day through food sources alone. This is when supplements may be useful.
Biotin supplement options
Biotin is included in many multivitamins, B-complex and hair/skin/nail supplements. It’s also available as a standalone supplement, including capsules, tablets and softgels.
Some things to look for in a quality biotin supplement:
- A reputable brand
- Sourced from bacteria or yeast
- No unnecessary fillers or additives
- USP verified for purity and potency
The biotin dosage can range from low amounts like 10 or 30 mcg up to very high doses of 10,000 mcg (10 mg) or more per serving.
Choose a dose within the recommended range of 100–300 mcg per day, or up to 5,000 mcg for hair growth. Start low and increase slowly to find the most effective dosage for you.
Too much biotin from supplements is unlikely to cause harm in the short term, as it’s water-soluble and any excess gets excreted in urine. However, there’s no evidence that mega-doses improve results.
Stick to the recommended range whenever possible. Consult your healthcare provider before taking any supplements, especially in high doses or long term.
How long until you see results?
Patience is key when taking biotin for hair growth. It can take 2–6 months of consistent supplementation and a healthy diet to notice significant improvements in rate of growth and thickness.
In studies showing positive effects, benefits have been reported after around 3–6 months of daily biotin use (1, 2, 4).
Give biotin at least 90 days before deciding if it works for you. Be consistent and take it as directed each day, rather than on and off.
For best results, biotin should be combined with a nutritious diet, gentle hair care, and treatments that address other underlying causes of your hair thinning or loss.
Who should not take biotin?
Biotin from food does not need to be restricted. However, there are some instances where biotin supplements should be used cautiously or avoided:
- Pregnant women, unless advised by their doctor. Very high doses above the RDA have not been studied for safety during pregnancy and breastfeeding.
- People taking medications for epilepsy. High dose biotin could interfere with anti-seizure lab tests, leading to inaccurate results.
- Those scheduled for lab testing. Biotin supplements can skew results for some blood and other medical tests, so they may need to be stopped temporarily.
- Individuals with a biotinidase deficiency. This is a rare inherited disorder where biotin builds up abnormally in the body. Those with this condition may need to avoid supplements.
Talk to your healthcare provider before taking biotin supplements if you have any medical conditions or take medications, especially anti-seizure drugs. Show them the supplements you are taking and doses.
Biotin side effects
Biotin is generally well tolerated, even at doses well above the RDA. Side effects are mild and uncommon.
Possible side effects may include:
- Skin rashes and other allergic reactions
- Nausea and digestive upset
- Balding when doses exceed 10,000 mcg per day, but this is reversible when the dose is reduced (8).
High biotin intake may also alter results of certain medical laboratory tests, like tests for heart disease, thyroid disease, and hormone status. Let your healthcare provider know about any supplements you are taking.
Stick to recommended dosages whenever possible. Report any unusual symptoms to your healthcare professional promptly.
The bottom line
Biotin is an essential B vitamin that may help with hair growth when ingested in supplement form or from food.
Doses of 100–300 mcg per day are typically recommended for supporting hair health. Some take up to 5,000 mcg daily for enhanced benefits, but more is not necessarily better.
Give biotin supplements at least 3 months for best results. Combine with a nutritious diet, gentle hair care practices, and treatments for any underlying issues causing hair thinning or loss.
Though generally safe, very high doses have not been well studied. Stick to the recommended dosages whenever possible and consult a healthcare provider before use if pregnant, breastfeeding or taking medications.