T3 uptake is an indirect measurement of the available binding sites for the thyroid stimulatory hormones from the brain. T3 uptake is not a measurement of T3 and should never be used alone. It is best used in conjunction with T4 and Free T3. T3 uptake can be abnormal with thyroid dysfunction, malnutrition, and kidney disease. Additionally, abnormal T3 uptake can be seen with use of oral contraceptives and hormone prescriptions such as testosterone and estrogen. Fasting is not required for this test. Take all medications as prescribed. This test is included in the Complete Thyroid Panel.