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T3-Free Free Tri-Iodothyronine Serum

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Free T3 Test Overview

A T3 (Triiodothyronine) test is used to diagnose problems in the thyroid gland. T3 (triiodothyronine) circulates in the body in a bound form with thyroxine-binding globulin and albumin. Less than 0.3% of the total T3 is a free fraction (FT3) and is the active form. T3 is one of the two main important thyroid hormones. A healthcare provider will draw a blood sample to test T3 levels.

Triiodothyronine usually occurs in two forms, free T3 and bound T3. A free T3 test is useful to determine whether a thyroid replacement therapy is working effectively. It can also help in diagnosing abnormalities related to proteins that bind different thyroid hormones. Free T3 is a second or third-level test related to thyroid function. It is used to obtain confirmation for hyperthyroidism.

Written by: Dr Vishal Wadhwa, M.D, D.N.B Microbiology, Medical Affairs

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T3-Free Free Tri-Iodothyronine Serum Price

Metropolis Healthcare is a leading diagnostics centre and pathology lab in India equipped with the latest state-of-the-art technologies that provides the T3-Free Free Tri-Iodothyronine Serum with a clear pricing structure.

The T3-Free Free Tri-Iodothyronine Serum Price in Mumbai is ₹ 355 .

We are committed to deliver accurate and quality results from the best labs in India with complete transparency regarding test cost and turnaround time. No matter where you are, we strive to offer patients high-quality service that is affordable and accessible.

Frequently Asked Questions

Free T3 test is done to support the results of FT4 & TSH. In a very small group of patients only T3 & FT3 is increased.
In pregnancy & other conditions an increase in thyroglobulin or albumin causes increase of T3 & T4 levels, without actually impacting body functions hence testing FT3 and FT4 is more representative

Free T3 test measures levels of FT3 hormone in blood

A free T3 blood test measures the levels of FT3 in your blood. This form of hormone enters the tissues in the body wherever it is needed. There are some blood tests which can measure both, free T3 and bound T3 and it is called a total T3 test.

Free T3 test requires a blood sample. A tourniquet (elastic) band is placed tightly on the upper arm. The patient is then asked to make a fist. This helps in the build-up of blood filling the veins. The skin is disinfected before needle insertion and the blood sample is collected in vacutainer.

High TSH & high T3/FT3 and T4/FT4: Thyroxine replacement therapy; pituitary adenoma; drugs like heparin, amiodarone, beta blockers, steroids; neonates; resistance to thyroid hormones
High TSH & low T3/FT3 and  T4/FT4: Autoimmune thyroiditis, thyroidectomy, post-radiation, iodine deficiency, thyroid infiltrating tumour/ amyloid
Low TSH & Low T3/FT3 and T4/FT4: Central hypothyroidism, non-thyroidal illness
Low TSH & High T3/FT3 and FT4: Grave's disease, toxic multinodular goitre, toxic adenoma, thyroiditis, drugs, hyperemesis gravidarum & hydatiform mole, congenital hyperthyroidism

. A free T3 test on its own does not provide reliable results. However, depending on the circumstances, your healthcare provider may still ask you to get the test done. In healthy people, the normal range of free T3 is as follows:


  • Infants up to 3 days old: 1.4 – 5.4 picograms per millilitre (pg/mL).
  • Infants 4 to 30 days old: 2.0 – 5.2 pg/mL.
  • Babies 1 month to 1 year old: 1.5 – 6.4 pg/mL.
  • Children 1 to 6 years old: 2.0 – 6.0 pg/mL.
  • Children 7 to 11 years old: 2.7 – 5.2 pg/mL.
  • Children 12 to 17 years old: 2.3 – 5.0 pg/mL.
  • Adults 18 to 99 years old: 2.3 – 4.1 pg/mL.

If the test results are higher than these normal levels, then it is indicative of hyperthyroidism. This means an overactive thyroid gland. It can result due to Grave’s disease, thyroid nodules and thyroiditis.

If the results of the test show that the total T3 or free T3 levels are high, it can mean that the person is suffering from hyperthyroidism. However, low levels of T3 can mean that the person is suffering from hypothyroidism. It is a type of condition in which the body is not making enough thyroid hormone.

Usually, a doctor will compare the results of the T3 test with T4 and TSH to diagnose whether or not a person has thyroid.

Usually, many changes can occur to the thyroid gland during pregnancy. As such, such changes are not very serious. Usually, pregnant women will not need a T3 test. However, a doctor can ask someone to take a T3 test during pregnancy if they are facing conditions such as symptoms of thyroid disease, a past record of thyroid disease, an autoimmune disease, or a family case of thyroid disease.

In cases of hyperthyroidism, usually both T4 and T3 (both total and free) are found to be elevated. But in some cases, only T3 levels may be elevated. In most cases, a total T3 test is sufficient for diagnosis but sometimes, free T3 may also be needed to be done. They are usually helpful in the case of patients who have a different distribution of binding proteins, such as in the case of pregnancy

You will need to get a Free T3 test done when your doctor suspects that you have a problem with your thyroid function. You could be experiencing certain symptoms related to the thyroid. These could be one or more of the following:

  • Changes in the weight
  • Feeling of fatigue
  • Increased frequency of bowel movements
  • Loss of hair
  • Increase in appetite
  • Increase in sweating
  • Irregularities in menstruation
  • Palpitation of the heart
  • Sleeping trouble
  • Increased nervousness or anxiety
  • Problems in concentrating

A free T3 is most useful in the diagnosis of hyperthyroidism. This is because it is the last hormone to get abnormal in the case of hypothyroidism.

  • Free T3 (Triiodothyronine) Test
  • FT3 (Free Triiodothyronine)
  • T3 (Triiodothyronine), Free, Serum
  • Triiodothyronine, Free
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