According to MedLine Plus, normal ranges for the Thyroid Stimulating Hormone (TSH) test are 0.4 to 4.0 milli-international units per liter (mIU/L) with slight variations based on specific standards by laboratory. A normal TSH level varies for women who are pregnant.
Physicians use TSH tests to determine if the thyroid is functioning properly. The butterfly-shaped thyroid gland secretes hormones that regulate a variety of bodily functions. A TSH test is generally ordered based on symptoms that correlate with overactive or underactive thyroid. To test TSH, blood is drawn and assessed by the laboratory. Thyroid function outside of the normal range may be overactive (hyperthyroid) or underactive (hypothyroid).