What Factors Can Affect Thyroid Test Results?

Various factors can affect thyroid test results, including medications (such as thyroid hormone replacement therapy, corticosteroids, and certain antithyroid drugs), pregnancy, illness, stress, fasting, and the timing of the test (some tests may be affected by circadian rhythms). It’s important to inform your healthcare provider about any medications, supplements, or medical conditions you have before undergoing thyroid testing.