Free T4 (Thyroxine) Test

Can medications affect Free T4 results?

Yes, biotin supplements, certain heart medications like amiodarone, and steroids can all influence Free T4 readings, so it's important to disclose your full medication list to your doctor.

Why does my doctor check both TSH and Free T4?

Together, these two values reveal not just whether thyroid hormone levels are abnormal, but also whether the problem originates in the thyroid itself or further upstream in the pituitary gland.