Blood tests for thyroid hormone levels provide the information necessary to keep the levels within the normal range and decide on appropriate individualized therapy for a patient according to his specific condition. If the patient is diagnosed with low thyroid levels (hypothyroidism), a TSH test is opted once a year to check that levels are within the normal range. If the levels are higher (hyperthyroidism), TSH and T4 (FT4) levels will be assessed, and the frequency of testing will depend on the selected treatment.