What Do the Thyroid Ranges on a Test Mean?

The ranges on a thyroid test generally indicate the blood's content of thyroid-stimulating hormone. There are also thyroid tests that measure the levels of thyroid hormones, and each has its own normal range and value, according to WebMD.

TSH levels for adults are normal when between 0.4 and 4.2 microunits per milliliter of blood. For children, normal levels are 0.7 to 6.4 microunits per milliliter. These ranges vary depending on the lab performing the test. TSH levels outside of the normal range do not always indicate thyroid problems, explains WebMD.

Elevated TSH levels may indicate an underactive thyroid or a pituitary gland tumor. Taking too small a dose of thyroid hormone medicine can also cause elevated TSH levels. Low TSH values may indicate an overactive thyroid, pituitary gland damage, too large a dose of thyroid hormone medicine or first-trimester pregnancy. There are cases in which a TSH level test may be inappropriate or ineffective. Those taking medications such as corticosteroids, dopamine or lithium may not receive valid test results. Also, chronic illness, stress or recent tests with radioactive materials may render the test ineffective, reports WebMD.

Other tests for thyroid problems include measurement of thyroid hormones T3 and T4, according to WebMD. The normal range for the T3 hormone is 80 to 180 nanograms per deciliter. The normal range for the T4 hormone is 4.6 to 12 micrograms per deciliter, explains EndocrineWeb.