Something I’ve been telling clients for years now is they need to stop taking biotin supplements if they are going to have a blood test soon. The current recommended dose of biotin for adults is 30 ug/day however it is commonly found in supplements at levels from 5 mg up to 20 mg. While the amount of biotin naturally received through dietary means is not enough to interfere with clinical tests, the levels found in these supplements can generate significant errors.
A wide variety of laboratory tests rely on biotin as a component of the assay. These include endocrine and autoimmune tests, as well as those for malignancy and heart damage markers. In 2017, Holmes et al. reviewed the manufacturer’s instructions for 374 methods performed by eight of the most popular immunoassay analyzers in the United States and found that 59% relied on biotin-based methods.
Biotin mainly interferes with two types of clinical assays. The first is called a sandwich assay. Although the design of these assays as used by some companies makes them relatively immune to biotin interference, many are still susceptible. The sandwich assay is commonly used to determine levels of TSH, β-hCG, PTH, insulin, ferritin, pro b-type natriuretic peptide, prostate-specific antigen, and others. The other type of assay in which biotin interference can play a significant role is called a competitive assay. This type of assay is typically used to measure levels of small steroids and other molecules, including free T4, total T4, free T3, total T3, cortisol, and 25-hydroxyvitamin D (calcifediol).
For most people, 3-4 days off biotin supplements is enough to clear it from your body to get an accurate blood test.
Here’s a very interesting case study about a woman who took biotin and it influenced her blood tests dramatically.
Here’s the link: Clinically Significant Lab Errors due to Vitamin B7 (Biotin) Supplementation: A Case Report Following a Recent FDA Warning - PMC.