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9 February 2018.

Many people take biotin tablets because they believe they will improve their hair, skin and nails. Laboratory workers have known for some years that large doses of biotin can lead to incorrect results for thyroid function tests. Other tests affected by biotin include those for heart attack, heart failure, cancer, anaemia and pregnancy. The errors can either increase or decrease results, and are greater the higher the dose. The EU recommended intake for biotin is only 0.05 mg (50 µg or mcg) a day, and vitamin supplements commonly contain this safe amount. However, much higher levels can be found in supplements widely promoted to benefit hair, skin and nails that contain up to 10 mg, 200 times the recommended intake, which can lead to interference in laboratory tests.

The most striking interferences with lab test results have occurred in patients taking extremely large doses of up to 600 mg a day as part of trials for the treatment of progressive multiple sclerosis. The company sponsoring the biotin trials withdrew its application for licensing in December 2017 after the European Medicines Agency considered the available data for improvement and safety to be insufficient. The firm hopes a further large international trial will complete in 2019. Those involved are aware of biotin’s effect on lab tests.

The earliest laboratory investigations of biotin interference were carried out by adding it to normal blood and measuring the effect. To study the real life effects of biotin and its metabolic break-down products, Dr Danni Li from the University of Minnesota and colleagues investigated blood samples from six healthy adult volunteers before and after they had taken 10 mg of biotin daily for seven days. They reported the performance of 37 lab tests for 11 substances on four major diagnostic systems online in the Journal of the American Medical Association on 26 September 2017. All 37 tests used antibodies (immunoassays), 23 with a biotin-streptavidin reagent and 14 without to act as controls. None of the control results showed interference; of the 23 with biotin-streptavidin, five of the eight that used what is called a competitive immunoassay gave falsely high results while four of the 15 that used what is called a sandwich immunoassay gave falsely low results. The authors recommend that further studies should include patients with abnormal initial test results.

On 28 November 2017 the US Food & Drug Administration (FDA) published a Safety Communication addressed to people taking or considering taking biotin supplements, doctors requesting lab tests, lab personnel and lab test developers warning about their possible effects on lab test results. Here are some practical suggestions arising from the FDA Recommendations for Consumers:

  • If you are taking daily multivitamins, look at the daily dose of biotin (which may also be called coenzyme R, vitamin B7 or vitamin H). A dose difficult to read on the bottle is often clearer in an online advertisement. Though most multivitamin preparations sold in the UK contain biotin, the dose is usually the recommended intake, 0.05 mg (50 µg) a day, or less and there will be no test interference.
  • You should let your doctor know if you are taking biotin tablets of known strength, especially tablets of 200mg (100,000 µg) or any tablets promoted for hair, skin and nails if, during a consultation, he or she suggests a lab test. You could be recommended to stop taking the tablets for a few days before the test to allow the biotin to be cleared from your body. (This is not necessary if you are taking Boots’ Skin, Hair and Nails Tablets as they contain only 0.045 mg of biotin.)
  • Should you develop an acute condition that requires hospital admission while taking biotin or hair, skin and nails tablets, it is essential you tell the doctors as it is likely you will need immediate lab tests. The doctor requesting an urgent test will inform the lab staff who can ensure that for appropriate tests a non-biotin-streptavidin analytical system is used. If one is not available, the sample can be depleted of biotin using streptavidin-coated microparticles as described by Christina Trambas from Collingwood, Australia and colleagues on 1 January 2017 online in the Annals of Clinical Biochemistry.