A TSH blood test measures thyroid-stimulating hormone levels to assess how well the thyroid gland is functioning. It is commonly used to diagnose and monitor thyroid conditions such as hypothyroidism and hyperthyroidism. The test requires a small blood sample and is highly sensitive to thyroid hormone changes. TSH testing is often the first step in thyroid evaluation and may be followed by additional hormone tests if results are abnormal. Regular TSH blood tests support effective treatment planning and long-term thyroid health management.