As far as supplements go, biotin is pretty safe. This B vitamin plays a major role in metabolism, and many people take it to improve the condition of their hair, skin and nails. Biotin is water soluble, meaning excess is excreted in urine; unlike fat-soluble vitamins, it's almost impossible for excessive amounts to build up in the body.
According to the National Institutes of Health (NIH), even doses up to 200 mg — 200,000 mcg — do not produce toxicity symptoms. However, high levels of biotin may interfere with important lab results.
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Biotin in Supplements
Biotin is widely available as a nutritional supplement in varying strengths. Biotin 5,000 mcg and biotin 10,000 mcg are common doses. This is well above the adequate intake, or AI, established as sufficient to meet the needs of most adults. For adult males and females, the NIH states that the AI is 30 mcg per day. Daily needs increase slightly to 35 mcg for breastfeeding women.
Biotin 10,000 mcg provides 33,333 percent of the AI. It's also sold in strengths of 15,000 mcg, and many people take even more than that each day. Yet, there have been no reports of toxicity from the supplement.
Read more: How Much Is Too Much Vitamin B Complex?
No Biotin Side Effects, But ...
While there are no side effects from having too much biotin in your system, the excess could cause another major issue that shouldn't be ignored. The Food and Drug Administration (FDA) reports that the high levels of biotin in supplements can cause clinically significant errors in lab test results. Many lab tests utilize biotin because it bonds with proteins that, when measured, can reveal certain health problems. Hormone tests and those that look for signs of heart conditions are examples of tests that may be compromised by a large intake of biotin from supplements.
The result is false high or low test results that can cause lab technicians and doctors to miss or misdiagnose a serious condition. The patient won't receive the proper treatment, and the condition could worsen undetected. The FDA reports one death due to incorrect test reports that falsely reported low levels of a biomarker used in diagnoses of heart attacks.
How Much Do You Really Need?
If your doctor has recommended a biotin supplement and she's aware of your biotin status, you don't have anything to worry about. Doctors sometimes recommend high-dose biotin supplements for certain conditions, including multiple sclerosis, says the FDA.
If you don't have a particular condition for which your doctor thinks biotin could be helpful, then you likely don't need a supplement. Biotin deficiency is rare, and there have been no cases of severe deficiencies in people who eat a normal, varied diet, according to the NIH.
The reason biotin supplements are so popular for hair, skin and nail health is that biotin deficiency causes hair loss, brittle nails and skin rashes. In that case, supplemental biotin would help improve the condition of the hair, skin and nails by repairing the deficiency. However, in healthy people, supplemental biotin likely has little effect. According to the NIH, only a handful of case reports and small studies have shown that biotin may promote hair growth and nail health, and these were very specific situations and poorly organized studies.
Rather than risk interfering with critical test results, you can get all the biotin you need from a healthy diet containing biotin-rich foods like eggs, salmon, sunflower seeds, sweet potatoes and broccoli.
Read more: Foods That Are High in B Vitamins