A TSH (thyroid-stimulating hormone) blood test measures the level of TSH in the blood. TSH is a hormone produced by the pituitary gland that stimulates the thyroid gland to produce and release thyroid hormones.

The TSH blood test is primarily used to evaluate thyroid function and diagnose conditions related to the thyroid gland. It may also be used to monitor treatment for thyroid conditions such as hypothyroidism or hyperthyroidism.

During the test, a healthcare professional will draw a blood sample from your arm and send it to a laboratory for analysis. The results of the test are reported as the level of TSH present in your blood, usually measured in milliunits per liter (mU/L).

Normal levels of TSH in the blood vary depending on the age of the individual, as well as the specific laboratory and testing method used. In general, normal TSH levels are between 0.4 and 4.0 mU/L.

Abnormal levels of TSH may indicate a problem with thyroid function. High levels of TSH may indicate hypothyroidism, a condition in which the thyroid gland does not produce enough thyroid hormones. Low levels of TSH may indicate hyperthyroidism, a condition in which the thyroid gland produces too much thyroid hormones.

If your TSH levels are abnormal, your healthcare provider may recommend additional tests, such as a free T4 blood test or imaging studies, to confirm the diagnosis and determine the appropriate treatment. Treatment for thyroid conditions may include medications to regulate thyroid hormone production, surgery to remove part or all of the thyroid gland, or other therapies depending on the specific condition.

Overall, the TSH blood test is a useful tool for evaluating thyroid function and diagnosing conditions related to the thyroid gland. If you have symptoms such as fatigue, weight changes, or other signs of thyroid dysfunction, or have been diagnosed with a related condition, it is important to talk to your healthcare provider about whether a TSH blood test or other tests may be appropriate for you.