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Formal name: Free triiodothyronine
Related tests: TSH; Total T4; Total T3; FT4

At a Glance

Why Get Tested?

To help diagnose hyperthyroidism

When to Get Tested?

If you get an abnormal TSH , T4 or FT4 result

Sample Required?

A blood sample taken from a vein in the arm

Test Preparation Needed?

None needed; however, certain medications can interfere with the FT3 test, so tell your doctor about any drugs that you are taking