Biotin

Is biotin safe?

Biotin (vitamin B7) is about as close to non-toxic as a vitamin gets. No upper limit has been set in the US, and the Linus Pauling Institute reports that 5 mg (5,000 mcg) a day for two years caused no adverse effects. People with inherited disorders of biotin metabolism take up to 200 mg a day, and multiple sclerosis trials used 300 mg a day.

The risk is a strange one. Biotin does not harm your body, but it can fool the blood tests doctors rely on. In November 2017 the FDA warned that high-dose biotin can cause falsely high or falsely low results, and said it had received a report of one patient who died after a troponin test, used to diagnose heart attacks, came back falsely low.

How does biotin interfere with lab tests?

Many modern immunoassays use the very tight bond between biotin and a protein called streptavidin to capture what they measure. If your blood is full of biotin from a supplement, it competes in that reaction. Depending on the test design, the result can come out too low or too high.

Tests known to be affected include:

• Troponin, the main blood test for a heart attack. A falsely low result can mean a missed diagnosis.
• Thyroid tests (TSH, free T4, free T3). Biotin can produce a pattern that looks like an overactive thyroid.
• Reproductive hormones and other markers measured with the same technique.

The FDA updated its warning in 2019 because it kept receiving reports of falsely low troponin results. Some test makers fixed their assays; others did not. As of 2022 the FDA still listed 17 troponin tests from companies including Roche, Siemens and Ortho-Clinical Diagnostics that had not addressed the problem. In the SPI2 trial of 300 mg a day for multiple sclerosis (The Lancet Neurology, 2020), biotin still caused inaccurate lab results despite the steps taken to prevent it.

The dose matters. A multivitamin with 30 mcg is not the issue. The FDA noted that hair, skin and nail supplements can contain up to 20 mg, more than 650 times the daily need, and those are the products that cause trouble.

Do you need biotin at all?

Probably not. Adults need about 30 mcg a day, and most people eat 40 to 60 mcg from eggs, nuts, seeds, liver and other foods. Deficiency is rare outside long-term raw egg white diets, some inherited conditions and long-term use of anticonvulsants such as carbamazepine, phenytoin and primidone, which lower biotin levels.

The beauty claims are weak. According to the Linus Pauling Institute, there are no published studies showing that high-dose biotin prevents or treats hair loss in healthy people. Three small uncontrolled trials of 2.5 mg a day suggested thicker, less brittle nails. In multiple sclerosis, a large trial (SPI2, 642 patients) found no meaningful benefit from 300 mg a day.

What is in the bottle?

Biotin is a stable molecule and most products are simple tablets, so label accuracy is less of a worry than with herbs or probiotics. There are exceptions. FDA sample testing led to two recalls listed in its public enforcement database: a 1,000 mcg product that held 0.8% of its label claim (2020) and a 5,000 mcg "maximum strength" product with no detectable biotin (2023). Combined "hair, skin and nails" formulas add their own problems; one biotin-collagen-keratin capsule was recalled in 2021 for undeclared fish collagen, an allergen.

Who should be careful

• Anyone having blood tests, especially for chest pain, thyroid problems or fertility. Tell the doctor and the lab about any biotin, including in multivitamins and beauty blends. If a result does not fit your symptoms, ask whether biotin could be the cause.
• People with thyroid disease, whose dose of levothyroxine or other thyroid medicine may be changed on the strength of a test that biotin has skewed.
• People going to an emergency department with chest pain. Mention biotin early.
• People on anticonvulsants, who may run low on biotin and should discuss it with their doctor.

How we scored it

Organ toxicity (88) and dose safety (82) are strong because biotin has no known toxic dose. Interactions (70) is the weakest factor: drug interactions are few, but interference with troponin and thyroid tests has led to a reported death and misdiagnoses. Regulatory actions (78) reflect FDA's repeated warnings rather than any ban, and quality (75) reflects two FDA recalls of products with almost no biotin. Many beauty blends pair biotin with collagen; vitamin B12 is another B vitamin with a wide safety margin.