What Is a Normal TSH Level?

A TSH level measures the amount of thyroid-stimulating hormone in the blood. This hormone, which is made in the pituitary gland, triggers the thyroid gland to release the hormones T4 and T3.

Significance

• A TSH level is drawn to monitor the effectiveness of thyroid hormone replacement medications and to diagnose a thyroid disorder or pituitary dysfunction.

The Test

• A blood sample for a TSH level is drawn by a phlebotomist or nurse from a vein in your arm or hand. The blood sample is sent to a laboratory for processing. Fasting is not required before having a TSH level drawn.

Results

• According the MedlinePlus.com, a normal TSH level is between 0.4 and 4.0 mlU/L. If you have a thyroid disorder and are receiving treatment, your physician may want to keep your thyroid level between 0.5 and 3.0 mlU/L.

Considerations

• Different laboratories may have slightly different normal ranges for a TSH level. Your physician will decide if your TSH level is abnormal.

Abnormal Levels

• An increased level of TSH may indicate thyroid dysfunction, infection of the thyroid gland, thyroid agenesis and congenital cretinism. A decreased TSH level may indicate pituitary dysfunction and hyperthyroidism.