To diagnose hyperthyroidism, a healthcare professional may order blood tests to gauge the levels of thyroid hormones in the body, such as thyroid-stimulating hormone (TSH), and perform a thorough clinical assessment. Other tests that may be performed include thyroid ultrasound, thyroid radioactive iodine uptake, and additional thyroid hormone levels like triiodothyronine (T3), thyroxine (T4), or free T4 (FT4).