I've noticed on many posts that Biotin, along with Vitamin D, Folate and Ferritin are recommended for testing to determine deficiencies that can cause low thyroid function.
What is the mechanism for low biotin levels affecting thyroid function? Or is it that hypothyroidism causes a biotin deficiency with the result being similar symptoms?
Just to be clear: This isn't a question about thyroid lab test results being skewed by those who take megadoses of biotin (>20mg/day).
it’s not that you need biotin tested
It’s that biotin is used in many labs tests so it’s important NOT to be taking biotin before a blood test
If taking biotin and lab test uses biotin, it can cause false results
Many thyroid patients take vitamin B complex to improve low B12 and low folate
Vitamin B complex almost always contains biotin…..so it’s important to stop vitamin B complex 5-7 days before test
Biotin is also in many supplements for hair loss and brittle nails. Important to stop this at least a week before test, as likely a higher biotin dose
Kiefer I expect what you have read is along the lines of:
"Stop biotin 3 days before testing."
What it should say is:
"Stop any supplements containing biotin 3 days before you have thyroid bloods tested."
kiefer
It's B12 that is advised to test along with Vit D, Folate and Ferritin. Nowhere does anyone say to test biotin. It's advised to stop taking biotin 3-7 days before any blood test (not just thyroid) due it causing false results when biotin is used in the testing procedure (3 days for the lower dose of biotin in supplements, eg 400mcg, and 7 days for the larger amounts found in stand alone supplements and hair/nail supplements, eg 5mg or 10mg).
Yes, you're correct. my bad
Paper showing which thyroid hormone assays are sensitive to biotin
Taking a Covid antibody test. Stopping supplements
Effect of vitamins on thyroid blood test
Blood test 
biotin and test results
