Will iodine on skin affect throid test?

Iodine on the skin can interfere with thyroid function tests, such as the thyroid uptake and thyroid release tests. These tests measure the thyroid's ability to take up and release iodine. If iodine is applied to the skin, it can be absorbed and interfere with the test results.

For this reason, it is important to avoid using iodine-containing products on the skin, such as iodine tincture, povidone-iodine, and Lugol's solution, for several days before and during thyroid function testing.