A thorough medical history and physical exam are the first steps in diagnosing hypothyroidism or mild (subclinical) hypothyroidism. If the results lead your doctor to suspect you have hypothyroidism or subclinical hypothyroidism, you will have tests to confirm the diagnosis.
Blood tests are always used to confirm a diagnosis of hypothyroidism or mild hypothyroidism. The tests used most often are:
If the above tests are not normal, antithyroid antibody tests may determine whether you have the autoimmune disease Hashimoto's thyroiditis, in which the body's defense system attacks the thyroid gland.
Because of the possibility of intellectual disability in infants with hypothyroidism, every state in the United States tests newborns for hypothyroidism. If your baby was not born in a hospital, or if you believe your baby may not have been tested, talk to your doctor. Screening tests for hypothyroidism are not always accurate. Even if test results show no problem, watch your child for symptoms of hypothyroidism, such as poor appetite, not gaining weight, and dry skin.
Experts do not agree on whether adults who don't have symptoms should have a thyroid test. The American Thyroid Association and the American Association of Clinical Endocrinologists recommend that testing be considered for those older than age 60.2 The U.S. Preventive Services Task Force makes no recommendation for or against screening for people who do not have symptoms of thyroid problems. The USPSTF states that there is not enough evidence to support screening.3
Talk to your doctor about whether testing is right for you.