A TSH test measures the level of Thyroid Stimulating Hormone in your blood. TSH is produced by the pituitary gland and controls how much T3 and T4 hormones your thyroid releases. It is the most important test for detecting hypothyroidism (high TSH) and hyperthyroidism (low TSH). Doctors usually recommend this test when symptoms like fatigue, weight changes, hair loss, mood changes, irregular heartbeat, or neck swelling suggest a thyroid imbalance.

For the TSH test, a small blood sample is collected from a vein, and no fasting or special preparation is required. TSH is often tested along with T3 and T4 to provide a complete thyroid profile. The results help diagnose thyroid disorders, monitor treatment, and evaluate overall hormonal health.