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Does biotin have side effects?

Biotin, also known as vitamin B7 or vitamin H, is a water-soluble B vitamin that helps the body convert food into energy. It also plays an important role in the health of hair, skin and nails. Biotin supplements have become very popular for improving hair, skin and nail health. But some people wonder if biotin has any side effects.

What is biotin?

Biotin is a B vitamin that is also known as vitamin B7 or vitamin H. It is one of the B complex vitamins that are essential nutrients for human health. Biotin is water-soluble, which means the body does not store it. Excess biotin is flushed out through urine.

Biotin plays a key role in metabolizing fats, carbohydrates and proteins. It does this by acting as a coenzyme for several carboxylase enzymes involved in energy production from food. Biotin helps convert food into useable energy at the cellular level.

Biotin is also important for the health of skin, hair and nails. It plays a role in skin cell signaling that is important for retaining moisture in the skin and hair. Biotin may also help stimulate hair and nail growth.

Biotin deficiency

Biotin deficiency is rare but can occur in certain situations. Causes of biotin deficiency include:

  • Inborn errors in biotin metabolism – This is a genetic disorder where the body cannot properly process biotin.
  • Pregnancy – Biotin requirements increase during pregnancy.
  • Long-term use of certain anti-seizure medications – Some medications like phenytoin, primidone and carbamazepine may lower biotin levels.
  • Long-term antibiotic use – Antibiotics can kill beneficial gut bacteria that help produce biotin.
  • Intestinal malabsorption – Issues with digesting and absorbing nutrients can lead to biotin deficiency.
  • Alcoholism – Long-term alcohol dependency is associated with low biotin levels.

Signs and symptoms of biotin deficiency include:

  • Hair loss
  • Dry, scaly skin and rashes
  • Brittle nails
  • Depression and lethargy
  • Cradle cap in infants
  • Neurological symptoms like seizures, paresthesias and altered mental status

Pregnant women are at higher risk of biotin deficiency which can impact fetal development. Biotin deficiency is treatable through increased biotin intake either through diet or supplements.

Biotin food sources

Biotin is found naturally in a wide variety of foods. The best food sources of biotin include:

  • Organ meats like liver and kidney – 3-5 oz contains 30-35 mcg biotin
  • Fish like salmon and tuna
  • Eggs and dairy products like milk and cheese
  • Seeds and nuts like almonds, peanuts and walnuts
  • Sweet potatoes, carrots and mushrooms
  • Bananas, raspberries, strawberries and avocados
  • Whole grains like oats, wheat germ and brown rice
  • Soybeans, legumes and lentils
  • Yeast
  • Leafy greens like spinach

The recommended daily intake for biotin is:

  • Infants up to 6 months – 5 mcg/day
  • Infants 7-12 months – 6 mcg/day
  • Children 1-3 years – 8 mcg/day
  • Children 4-8 years – 12 mcg/day
  • Children 9-13 years – 20 mcg/day
  • Adolescents 14-18 years – 25 mcg/day
  • Adults 19+ years – 30 mcg/day
  • Pregnant women – 30 mcg/day
  • Breastfeeding women – 35 mcg/day

Most people can get adequate biotin through a varied, balanced diet. But some choose to take biotin supplements to increase their intake.

Biotin supplements

Biotin supplements have become a popular supplement in recent years, especially for hair, skin and nail health. Biotin supplements are available as capsules, tablets and softgels in doses ranging from 30 mcg to 10,000 mcg.

Some of the claimed benefits of biotin supplements include:

  • Stronger nails
  • Thicker, fuller hair
  • Healthier skin
  • Reduced hair loss
  • Improved metabolism
  • Balanced blood sugar

However, there is limited scientific evidence to support many of these beneficial claims about biotin supplements. But biotin deficiency can lead to hair loss and skin/nail issues. And studies show biotin supplements can help treat a deficiency.

The FDA has not approved a Recommended Daily Allowance (RDA) for biotin supplements. Most supplements provide much higher doses than the recommended daily intake from food. For example, 5,000-10,000 mcg per dose compared to only 30 mcg RDI.

Biotin is generally considered safe, even at higher supplement doses. But very high doses may have some side effects in certain individuals.

Does biotin have side effects?

For most healthy people, biotin does not typically cause negative side effects. Since it is a water-soluble vitamin, excess biotin is excreted in urine. Mega-doses of biotin up to 200,000 mcg per day were found safe and well tolerated in clinical studies.

However, high doses of biotin may potentially cause side effects in some cases:

Interactions with lab tests

High doses of biotin can skew results on some lab tests, including:

  • Thyroid hormone levels
  • Cardiac troponin levels
  • Sex hormones like estradiol and testosterone

Biotin supplements may cause falsely high or low results on these tests. If you take biotin supplements, let your healthcare providers know to avoid testing errors.

Allergic reactions

Allergies to biotin supplements are rare but can occur. Some signs of a biotin allergy include:

  • Hives or itchy rash
  • Swelling of face, lips or tongue
  • Wheezing or difficulty breathing
  • Dizziness or fainting

Stop taking biotin and see a doctor immediately if you have an allergic reaction.

Interaction with medications

High doses of biotin could potentially interact with certain medications like:

  • Anti-seizure medications – biotin may lower drug levels
  • Antibiotics – biotin may reduce absorption
  • Lipid-lowering medications – biotin may decrease effectiveness

Talk to your doctor before taking biotin if you take any medications, especially anti-seizure drugs.

Gastrointestinal distress

Minor GI upset like diarrhea or nausea can sometimes occur with high doses of biotin. This is not common but has been reported in a small number of cases.

Hair loss

Ironically, while biotin supplements are often used to improve hair growth, there are some reports of hair loss or temporary hair shedding. However, research has not found biotin causes hair loss.

Skin rashes

Skin rashes have rarely been linked to biotin use. It’s not clear if biotin causes rashes or if they are due to other unrelated factors.

Kidney stones

There is no evidence that biotin alone causes kidney stones. But there is one case report of kidney stones occurring in a man taking very high doses of biotin along with vitamin B5 (pantothenic acid).

Who should not take biotin?

Biotin supplements are likely safe for most people at recommended dosages. But the following groups may want to avoid supplements or check with a doctor first:

  • Individuals taking anti-seizure medications – biotin may lower drug levels and increase risk of seizures.
  • People scheduled for thyroid lab tests – biotin may distort test results.
  • Those who are allergic or sensitive to biotin supplements.
  • People with impaired kidney function – excess biotin is removed through the kidneys.
  • Pregnant women – biotin is important during pregnancy but mega-doses have not been studied for safety.
  • Individuals undergoing chemotherapy – biotin may interact with some chemotherapy drugs.

Children and infants should not take biotin supplements without medical advice, except for treatment of a deficiency.


Biotin is a beneficial B vitamin that’s important for energy metabolism and healthy hair, skin and nails. Deficiency can lead to symptoms like hair loss and brittle nails.

Many people take biotin supplements to promote better hair, skin and nail health. Biotin is generally considered very safe, even at mega-doses up to 200,000 mcg per day.

However, high doses may cause side effects in certain groups or situations. Possible side effects include interference with lab tests, allergic reactions in sensitive individuals, medication interactions, GI upset and kidney stones in rare cases.

For most healthy adults, biotin supplements are safe when used at recommended dosages. But some people should check with a doctor before using high dose supplements, including those on medications, pregnant women, individuals with kidney impairment and those scheduled for thyroid lab tests.

Overall, research has not found strong evidence for biotin causing negative side effects in most people. But more research on the long-term safety of high dose supplementation is still needed.