A TSH Blood Test measures the level of thyroid-stimulating hormone (TSH) in your bloodstream to evaluate how well your thyroid gland is functioning. This test is commonly used to diagnose hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), as abnormal TSH levels can indicate hormonal imbalance. Physicians often order a TSH Blood Test if you experience fatigue, weight changes, cold sensitivity, or other thyroid-related symptoms. The procedure usually requires a simple venous blood draw at a lab, clinic, or doctor’s office. Results help guide medication adjustments and ongoing thyroid management.