BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuT3 testTriiodothyronine; T3 radioimmunoassay; Toxic nodular goiter - T3; Thyroiditis - T3; Thyrotoxicosis - T3; Graves disease - T3Triiodothyronine (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. Blood sampleVenipuncture is the collection of blood from a vein. It is most often done for laboratory testing.ImageRead Article Now Book Mark Article 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.Drugs that can increase T3 measurements include:Birth control pills Clofibrate Estrogens Methadone Certain herbal remedies Drugs that can decrease T3 measurements include:Amiodarone Anabolic steroids Androgens Antithyroid drugs (for example, propylthiouracil and methimazole) Lithium Phenytoin Propranolol 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 proteins and floating free in the blood.The free T3 test measures the T3 that is floating free in the blood. The tests for free T3 are generally less accurate than for total T3.Your provider may recommend this test if you have signs of a thyroid disorder, including: The pituitary gland does not produce normal amounts of some or all of its hormone (hypopituitarism) HypopituitarismHypopituitarism is a condition in which the pituitary gland does not produce normal amounts of some or all of its hormones.ImageRead Article Now Book Mark Article Overactive thyroid gland (hyperthyroidism) HyperthyroidismHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Underactive thyroid gland (hypothyroidism) HypothyroidismHypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. This condition is often called underactive thyroid....ImageRead Article Now Book Mark Article Taking medicines for hypothyroidism 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 picgrams 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 different measurements or test different specimens. Talk to your provider about the meaning of your specific test results.Normal values are age specific for people less than age 20. Check with your provider about your specific results. What Abnormal Results Mean A higher-than-normal level of T3 may be a sign of:Overactive thyroid gland (for example, Graves disease) Graves diseaseGraves disease is an autoimmune disorder that leads to an overactive thyroid gland (hyperthyroidism). An autoimmune disorder is a condition that occ...ImageRead Article Now Book Mark Article T3 thyrotoxicosis (rare) ThyrotoxicosisHyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often called overactive thyroid.ImageRead Article Now Book Mark Article Toxic nodular goiter Toxic nodular goiterToxic nodular goiter involves an enlarged thyroid gland. The gland contains areas that have increased in size and formed nodules. One or more of th...ImageRead Article Now Book Mark Article 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 first trimester) or with the use of birth control pills or estrogen.A lower-than-normal level may be due to:Severe short-term or some long-term illnesses Thyroiditis (swelling or inflammation of the thyroid gland -- Hashimoto disease is the most common type) Hashimoto diseaseChronic thyroiditis is caused by a reaction of the immune system against the thyroid gland. It often results in reduced thyroid function (hypothyroi...ImageRead Article Now Book Mark Article Starvation Underactive thyroid gland Selenium deficiency causes a decrease in the conversion of T4 to T3, but it is not clear that this results in lower than normal T3 levels in people. 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 include:Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma (blood buildup under the skin) Infection (a slight risk any time the skin is broken)Open ReferencesReferencesGuber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 24.Kim G, Nandi-Munshi D, Diblasi CC. Disorders of the thyroid gland. In: Gleason CA, Juul SE, eds. Avery's Diseases of the Newborn. 10th ed. Philadelphia, PA: Elsevier; 2018:chap 98.Salvatore D, Cohen R, Kopp PA, Larsen PR. Thyroid pathophysiology and diagnostic evaluation. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 11.Weiss RE, Refetoff S. Thyroid function testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 78.AllVideoImagesTogBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustrationBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustration Tests for T3 test T3 testT3RU testRelated Information Free T4 test(Medical Test)Hyperthyroidism(Condition)Protein in diet(Nutrition)T3RU test(Medical Test)Graves disease(Condition)Chronic thyroiditis (Hashimoto disease)(Condition)Thyroid cancer(Condition)Chronic(Special Topic)Hypothyroidism(Condition)Silent thyroiditis(Condition)Hypothyroidism(In-Depth) Review Date: 1/26/2020 Reviewed By: Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. 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