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At a Glance
Why Get Tested?
When to Get Tested?
When you have signs and symptoms of thyroid disease, usually after an abnormal result on a TSH test; commonly performed as a screening test on newborns soon after birth; when you are being treated for a thyroid disorder
A blood sample drawn from a vein in your arm or from pricking the heel of an infant
Test Preparation Needed?
None needed; however, certain medications can interfere with the free T4 test, so tell your healthcare provider about any drugs that you are taking. If you take thyroid hormone as treatment for thyroid disease, it is recommended that your blood sample be drawn before you take your dose for that day.