The TFT blood test, or thyroid function test, is a panel of blood tests that measures the levels of several hormones produced by the thyroid gland. The thyroid gland is a butterfly-shaped gland located in the neck that produces hormones that regulate metabolism and affect nearly every organ in the body.

The TFT blood test typically includes measurement of thyroid-stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) levels in the blood. In some cases, additional tests such as free T4 (FT4) or reverse T3 (rT3) may be included in the panel.

The TFT blood test is commonly used to evaluate thyroid function and to diagnose and monitor thyroid disorders, such as hypothyroidism and hyperthyroidism. It can also be used to evaluate other conditions, such as infertility, menstrual irregularities, and heart disease.

During the test, a small sample of blood is drawn from a vein in the arm and sent to a laboratory for analysis. The normal range for thyroid hormone levels varies depending on the laboratory that performs the test, but generally ranges from:

• TSH: 0.4 to 4.0 milli-international units per liter (mIU/L)
• T4: 4.5 to 12.5 micrograms per deciliter (mcg/dL)
• T3: 80 to 200 nanograms per deciliter (ng/dL)

Abnormal TFT results can indicate thyroid dysfunction or other conditions. For example, a high TSH level and low T4 level may indicate hypothyroidism, while a low TSH level and high T4 level may indicate hyperthyroidism. Additional tests, such as FT4 or rT3, may provide further information about thyroid function.

A healthcare provider can interpret the results of the TFT blood test in the context of the individual’s medical history and other test results, and develop an appropriate treatment plan if necessary.