Biotin Interference in Diagnostic Tests

Despite sobering evidence of no benefit or even possible harm, the use of vitamin and mineral supplements by adults continues to grow. It is estimated that the US supplement industry is now costing consumers over $30 billion annually. Laboratorians have long had to contend with potential analytical interferences due to ingested substances. Now, biotin has become a pervasive interferent, increasingly insidious and problematic to clinical laboratory testing. Biotin, also known as vitamin B7, is an essential coenzyme involved in carbon dioxide transfer in carboxylase reactions. The US Department of Agriculture–recommended Dietary Reference Intake (DRI)2 of biotin is 30 μg per day and supplementation is normally not necessary as biotin is ubiquitous in common foods. However, for the past several years, biotin has been marketed as a beauty supplement. One label on a biotin bottle reads, “For lustrous hair, radiant skin, and strong nails.” Although these beauty claims are not well supported, biotin's popularity is at an all-time high due to heavy marketing and receptive consumers. Because over-the-counter biotin is not regulated and is sold as a beauty product, there are no records of the actual amounts that are being ingested, but many tablets contain upwards of 10 mg, suggesting that consumers are taking amounts of biotin far in excess of the DRI. …