The T3 test, commonly referred to as the Triiodothyronine test, measures the level of the thyroid hormone T3 in the blood. T3 is crucial for regulating metabolism, energy production, and other bodily functions. The test is typically used to assess thyroid function, particularly in diagnosing hyperthyroidism or evaluating thyroid hormone imbalances. There are two forms of T3 in the blood: Total T3 (both bound and free) and Free T3 (unbound, active form). High or low levels of T3 can indicate thyroid disorders.

Hypothyroidism, Hyperthyroidism, Hashimoto's thyroiditis, Thyroid cancer.

The normal levels of T3 are mentioned in the table below. Thyroxine (T3) Results Total T3 0.97-1.80 ng/dL The T3 normal range in pregnancy Trimester Results Second trimester 1.7 - 4.3 nmol/L Third trimester 0.4 - 3.9 nmol/L The T3 normal range in newborn Age Results - T3 Cord Blood 15 to 75 ng/dL 1 to 4 days 100 to 740 ng/dL 4 to 30 days 105 to 387 ng/dL 1 to 12 months 105 to 245 ng/dL 1 to 5 years 105 to 269 ng/dL 6 to 10 years 94 to 241 ng/dL 11 to 18 years 80 to 210 ng/dL.

T3 test results show the level of the thyroid hormone triiodothyronine in the blood.

• Normal range: Typically, Total T3 is around 80-200 ng/dL, and Free T3 is about 2.3-4.2 pg/mL, though ranges can vary by lab.

• High T3 levels: May indicate hyperthyroidism, where the thyroid is overactive.

• Low T3 levels: Can suggest hypothyroidism, where the thyroid is underactive, or other conditions like illness or malnutrition.

Abnormal results usually require further testing and clinical evaluation for a full diagnosis.