Beware of Biotin Interfering With Thyroid Tests

It’s alarming to get a laboratory test result that shows a serious problem. Learning later that the test might have given a false reading is also frustrating. One reader discovered that you should beware of biotin if you are having thyroid tests run.

Why Should You Beware of Biotin?

Q. My husband recently had blood tests that showed he was hyperthyroid. His doctor ordered further tests, including a thyroid scan and an iodine uptake test.

Then an endocrinologist mentioned that the thyroid blood tests can be affected by biotin. We checked our multi-vitamin, and there were 500 mcg of biotin! Normal RDA is 30 mcg. Others should be warned about this.

Biotin Can Interfere With Tests for TSH:

A. The usual test for thyroid-stimulating hormone (TSH) is subject to interference when biotin levels are high (Nutrition, Jan. 2019).  The result is that TSH appears lower than it actually is, leading to a false diagnosis of hyperthyroidism. When TSH is low, that is an indication that the pituitary gland in the brain is trying to shut down thyroid hormone production. Normally, that would be due to excess thyroid hormone in circulation. But biotin from B vitamins or other products can grab TSH and lower it artificially.

Doctors and patients should both beware of biotin giving a false result on thyroid tests. Patients might be wise not to take biotin-containing products, such as vitamins or hair-restoration products, when they are being tested for thyroid problems.

Learn More:

Biotin is not the only thing that can interfere with blood tests for thyroid function. You can find out about others in our eGuide to Thyroid Hormones.