Free T4 test

Thyroxine test; Total T4 test

T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood.

Blood test

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.

How the Test is Performed

How to Prepare for the Test

How the Test will Feel

Why the Test is Performed

Normal Results

What Abnormal Results Mean

Risks