T3 Blood Test (Free & Total) & Normal Range
This test measures the level of triiodothyronine (T3) in the blood. T3 is a hormone made by the thyroid. The test is most often used to diagnose hyperthyroidism, a disease in which the body makes too much thyroid hormone. Learn more. The T3 test measures triiodothyronine in blood to help doctors diagnose hyperthyroidism. The thyroid is a butterfly-shaped gland located at the base of your throat. Its job is to make and release hormones that circulate through your body via your blood. The hormones your thyroid makes help control how your body uses energy.
This blood test measures the level of the hormone triiodothyronine T3 in your blood. The hormone is made by your thyroid gland. The thyroid is a butterfly-shaped gland near the base of your throat, above your collarbones. The thyroid gland makes T3 in response to thyroid stimulating hormone TSH.
TSH rest made by the pituitary gland in bood brain. T3 works with another thyroid hormone called T4 to help control how your body stores and uses energy to do its work metabolism. The thyroid hormones help control many of your body's other processes, including:. The T3 test is used to help diagnose thyroid problems, such as hyperthyroidism. Hyperthyroidism means the thyroid gland makes too many thyroid hormones.
T3 has 2 forms: bound and free. Bound T3 is attached to a protein and free T3 is not attached to anything. The free T-3 test measures only the amount of free T3. The total T3 test measures both free and bound T3 in your blood. Eye irritation or bulging eyes these are symptoms of Graves' disease, a common cause of hyperthyroidism. You may also need this test if you have symptoms of hypothyroidism. This is when the thyroid gland does what are the best toe shoes make enough thyroid hormones.
Symptoms include:. Test results may vary depending on your age, bblood, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. The normal level of free T3 in the blood is 0. The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand.
Having a blood test with a needle tewt some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, tesy may feel a slight sting or pain.
Afterward, the site may be sore. Taking thyroid hormone medicines or certain other medicines, such as estrogen or methadone, can affect your test results. Eating a diet high b,ood iodine-rich foods, such as seaweed, may also affect your test results. You don't need to prepare for this test. But be sure your healthcare hwat knows about all the medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.
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Free and Bound Tesh Blood Does this test have other names? Triiodothyronine test, T3 test, thyroid function test, FT3. What is this test? The thyroid hormones help control many of your body's other processes, including: Breathing Heart function Nervous system function Body temperature Cholesterol level Metabolism how to rid your house of dog odor affects your weight Brain ks Moisture in the skin Menstruation The T3 test is yest to help diagnose thyroid problems, such as hyperthyroidism.
Why do I need this test? You may need this test if you have symptoms of hyperthyroidism. Symptoms include: Extreme tiredness Low tolerance for cold Weight gain Hair iss Swelling around eyes Slower heart rate Shortness of breath Constipation Menstrual irregularity Loss of consciousness rare. What other glood might I have along with this test? What do my test results mean? How is this test done? Does this test pose any risks? What might affect my test what is t3 blood test How do I get ready for this test?
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What is a triiodothyronine (T3) test?
3 rows · Jul 22, · Triiodothyronine, or T3, is a hormone that the thyroid gland produces. A T3 blood test can Author: Aaron Kandola. Dec 21, · A free T3 test only measures the amount of free T3 in the blood. Typically, the free T3 test is used to evaluate thyroid function because it is unaffected by variations in binding protein levels. However, because the amount of free T3 in the body is so tiny, it can be harder to get an accurate measurement of free T3 compared to total T3 [ 5 ]. What is being tested? Triiodothyronine (T3) is one of two major hormones produced by the thyroid gland, a small butterfly-shaped organ that lies flat across the windpipe at the base of the throat. The other major thyroid hormone is called thyroxine (T4) and together they help control the rate at which the body uses energy.
To help evaluate thyroid gland function; to diagnose thyroid disease , including hyperthyroidism , and determine the cause; to monitor effectiveness of treatment of a thyroid disorder. Acute illness may affect thyroid testing test results. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness.
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The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results. If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test s to obtain the reference range. Laboratory test results are not meaningful by themselves.
Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques.
This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits.
Triiodothyronine T3 is one of two major hormones produced by the thyroid gland, a small butterfly-shaped organ that lies flat across the windpipe at the base of the throat.
The other major thyroid hormone is called thyroxine T4 and together they help control the rate at which the body uses energy. Almost all of the T3 and T4 found in the blood is bound to protein.
The rest is free unbound and is the biologically active form of the hormone. Tests can measure the amount of free T3 or the total T3 bound plus unbound in the blood. Most of the hormone produced by the thyroid is T4. This hormone is relatively inactive, but it is converted into the much more active T3 in the liver and other tissues. T3 levels are regulated by the feedback system that the body uses to maintain stable amounts of thyroid hormones in the blood. T4 and TSH, along with its regulatory hormone thyrotropin releasing hormone TRH , which comes from the hypothalamus , are also part of the feedback system.
When all three organs hypothalamus, pituitary and thyroid are functioning normally, thyroid production is regulated to maintain relatively stable levels of thyroid hormones in the blood. If the thyroid gland produces excessive amounts of T4 and T3, then the person affected may have symptoms associated with overactive thyroid hyperthyroidism , such as nervousness, tremors of the hands, weight loss, insomnia, and puffiness around dry, irritated eyes and in some cases, bulging eyes.
Graves disease is the most common cause of hyperthyroidism. See the article on Graves Disease. If the thyroid gland produces insufficient amounts of T4 and T3, then the person may have signs and symptoms associated with underactive thyroid hypothyroidism and a slowed metabolism, such as weight gain, dry skin, fatigue, and constipation.
Hashimoto thyroiditis is the most common cause of hypothyroidism in the U. See the article on Hashimoto Thyroiditis for more details. Both hyperthyroidism and hypothyroidism can also be caused by thyroiditis , thyroid cancer , and excessive or deficient production of TSH. The effect of these conditions on thyroid hormone production can be detected and monitored by measuring the free T3 or sometimes total T3. A free or total triiodothyronine free T3 or total T3 test is used to assess thyroid function.
It is ordered primarily to help diagnose hyperthyroidism and may be ordered to help monitor treatment of a person with a known thyroid disorder. Most of the T4 and T3 circulates in the blood bound to protein, while a small percentage is free not bound. Blood tests can measure total T4 unbound plus bound , free T4, total T3 bound plus unbound , or free T3. Since most T3 is bound to protein, the total T3 can be affected by protein levels and protein binding ability, but the free T3 is not.
However, some professional guidelines recommend the total T3, so either test may be used to assess thyroid function. For example, free T3 or sometimes total T3 may be ordered along with thyroid antibodies to help diagnose Graves disease , an autoimmune disorder that is the most common cause of hyperthyroidism.
The free or total T3 test is usually ordered following an abnormal TSH , particularly if the free T4 test is not elevated. It may be ordered as part of the investigative workup when a person has symptoms suggesting hyperthyroidism , especially if the free T4 level is not elevated. Signs and symptoms may include:. Free or total T3 may sometimes be ordered at intervals to monitor a known thyroid condition and to help monitor the effectiveness of treatment for hyperthyroidism.
Total T3 or free T3 results are typically evaluated with other thyroid testing results i. In general, high total or free T3 results may indicate an overactive thyroid gland hyperthyroidism and low total or free T3 results may indicate an underactive thyroid gland hypothyroidism. The test results alone are not diagnostic but will prompt the healthcare practitioner to perform additional testing to investigate the cause of the excess or deficiency.
For example, in people with hyperthyroidism, free T4, free T3, and TSH are regularly checked while they are on anti-thyroid drugs to assure that the drugs are working and to decrease doses if thyroid hormone levels get too low. In people with hypothyroidism, TSH and free T4 are regularly checked to assure that the right dose of thyroid hormone is being given to make TSH normal. The following table summarizes some examples of typical test results and their potential meaning.
Adults with subclinical hypothyroidism may have few or no overt symptoms of hypothyroidism. However, subclinical hypothyroidism places affected adults at somewhat increased risk for an elevated LDL cholesterol level, increased risk for cardiovascular disease , and reduced mental acuity.
Adults with subclinical hyperthyroidism may have few or no overt symptoms of hyperthyroidism. However, subclinical hyperthyroidism places affected persons at somewhat increased risk for atrial fibrillation and osteoporosis. It is important to note that thyroid tests are a "snapshot" of what is occurring within a dynamic system.
Many multivitamins, supplements especially hair, skin, and nail and over-the-counter and prescription medications may affect thyroid test results, and their use should be discussed with the healthcare practitioner prior to testing. For example, biotin vitamin B7 can interfere with some lab tests, so your healthcare practitioner may advise you to refrain from taking biotin or supplements that contain biotin for a few days before having blood drawn for thyroid hormone testing.
If you have a procedure done in which fluorescein dyes are injected into your blood e. It is determined from the total T4 test and some estimation of the level of thyroid hormone binding proteins. The T3 uptake test was the original test for estimating the level of binding proteins, and later versions were called T-uptake methods.
These are rarely used now that there are methods available to measure free T4 and free T3 directly. Normally, when the liver converts T4 to T3, it also produces a certain percentage of RT3. When the body is under stress, such as during a serious illness, it tries to prevent many tissues that depend on T3 from being metabolically active by producing more RT3 than T3. This is believed to be a way of conserving energy until the stress is relieved and it causes a syndrome called non-thyroidal illness NTI.
RT3 may also be elevated in hyperthyroidism. Use of the RT3 test remains controversial and it is not widely requested. Pregnancy causes normal changes in the function of many endocrine glands, including the thyroid gland. Some experts have advocated screening pregnant women during the first trimester or preconception even if they do not have a history of thyroid disease. However, most guidelines do not support this course of action. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research.
Learn More. Please note when you click on the hyperlinked code, you are leaving Lab Tests Online and accessing Loinc. Thyroid Tests. Wisse, B. T3 test. MedlinePlus Medical Encyclopedia. Sofronescu, A. Thyroid Screen Interpretation. Medscape Protocols. Erik, A. Straseski, J. Thyroid Disease. ARUP Consult. Thyroid Function Tests. American Thyroid Association. T3 Triiodothyronine , Total, Serum.
Mayo Clinic Mayo Medical Laboratories. Ross, D. Thyroid Volume 26, Issue Thomas, Clayton L. Taber's Cyclopedic Medical Dictionary. Pagana, Kathleen D. Brown, T.