Triiodothyronine; T3 radioimmunoassay

The range for normal values is 100 to 200 ng/dL (nanograms per deciliter).

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Greater than normal levels may indicate:

• High levels of a protein that carries T3 in the blood (may occur in pregnancy, with use of birth control pills or estrogen, liver disease, or as part of an inherited condition)
• Hyperthyroidism (for example, Graves disease)
• T3 thyrotoxicosis (rare)
• Thyroid cancer (rare)

Lower than normal levels may be due to:

• Long-term illness
• Hypothyroidism (for example, Hashimoto's disease)
• Starvation

Other conditions under which the test may be performed:

• Painless (silent) thyroiditis
• Thyrotoxic periodic paralysis
• Toxic nodular goiter

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T3 test Overview

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T3 test Risks

Review Date: 04/20/2010
Reviewed By: Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)