LAB TEST
T3 test
Triiodothyronine (T3) is a thyroid hormone. It plays an important role in the body's control of metabolism (the many processes that control the rate of activity in cells and tissues). A laboratory test can be done to measure the amount of T3 in your blood.
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
Your health care provider will tell you if you need to stop taking any medicines before the test that may affect your test result. Do not stop taking any medicine without first talking to your provider. Medicines that can increase T3 measurements include: Birth control pills Estrogens Methadone Certain herbal remedies…
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
Why the Test is Performed
This test is done to check your thyroid function. Thyroid function depends on the action of T3 and other hormones, including thyroid-stimulating hormone (TSH) and T4 . Sometimes it can be useful to measure both T3 and T4 when evaluating thyroid function. The total T3 test measures the T3 that is both attached to…
Normal Results
The range for normal values are: Total T3 -- 60 to 180 nanograms per deciliter (ng/dL), or 0.9 to 2.8 nanomoles per liter (nmol/L) Free T3 -- 130 to 450 picograms per deciliter (pg/dL), or 2.0 to 7.0 picomoles per liter (pmol/L) Normal value ranges may vary slightly among different laboratories. Some labs use…
What Abnormal Results Mean
A higher-than-normal level of T3 may be a sign of: Overactive thyroid gland (for example, Graves disease ) T3 thyrotoxicosis (rare) Toxic nodular goiter Taking thyroid medicines or certain supplements (common) Liver disease A high level of T3 may occur in pregnancy (especially with morning sickness at the end of the…
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others. Other risks associated with having blood drawn are slight, but may…
References
Faix JD. Thyroid function testing (thyrotropin, triiodothyronine, and thyroxine). In: Robertson RP, ed. DeGroot's Endocrinology . 8th ed. Philadelphia, PA: Elsevier; 2023:chap 68. Guber HA, Oprea M, Rusell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management…
This is a summary. Read the full article at www.ucsfbenioffchildrens.org (reviewed 28/02/2024).
This page is general information and is not medical advice. It does not replace a registered doctor, and it is not a prescription or a recommendation to use any medicine or test. Prices are listed prices and may change. Always follow the advice of your doctor or pharmacist.