Biotin, also known as vitamin B7 and nicknamed vitamin H, is present in many multivitamins. The recommended daily dose for adults is around 30 mcg (30 micrograms, which is much smaller than a milligram). However, some supplements promoted for hair, nail, and skin health contain biotin at much higher doses, as much as 10,000 mcg (over 30,000% the recommended daily need).
Consuming large amounts of biotin can be problematic. Some lab analyzers use an immunoassay that contains biotin. In patients with excess biotin in their blood samples, there is an increased risk of false lab values due to the inability of the patient’s blood to bind properly.
There is insufficient data to know if waiting for hours or days before running lab tests would help. Furthermore, waiting is obviously impractical when running critical lab tests such as for a heart attack or pregnancy.