T3 Test

Thyroid disorders

What is a T3 test?

A T3 test is done to measure the amount of T3 or triiodothyronine hormone present in the blood. The test is done to examine the thyroid functioning in our body and to detect if there is any thyroid problem. This test is also known as triiodothyronine or T3 radioimmunoassay test.

What is T3?

T3 or triiodothyronine is a hormone that is produced by the thyroid gland in our body. The T3 along with other hormones like T4 or thyroxine maintains our bodily functions like growth, temperature, heart rate, etc.

T3 can be of two types:

– T3 that is mostly found in the body is bound T3 which binds itself to the proteins and flows throughout the body.

– Free T3 which does not bind is less abundant and circulates throughout the blood.

The T3 test that is most commonly done is the T3 total test which measures both bound and free T3 in our blood.

Why do I need a T3 test?

Your doctor may ask you to do a T3 test if he suspects you have a thyroid problem. Possible symptoms that indicate a thyroid disorder include:

– Unexpected weight loss or gain.
– Sensitivity to heat and cold.
– Dryness in the skin.
– Puffy skin.
– Irritation or dryness in the eyes.
– An increase in heart rate.
– Loss of hair.
– Tremors in hand.
Menstrual irregularity.
Anxiety issues.

Do I need a T3 test if I have already been diagnosed with a thyroid disorder?

If you already have a thyroid problem, your doctor may prescribe a T3 test along with other thyroid tests. Your doctor may also order a T3 test if he suspects you have any of the following thyroid disorders:

Hyperthyroidism, a condition where your body is producing too much thyroid hormones.

Hypopituitarism whereby the pituitary gland is not producing enough pituitary hormones.

– Muscle weakness due to thyrotoxic periodic paralysis.

Hypothyroidism, when the body fails to produce normal thyroid hormones.

How do I prepare for the T3 test?


The test does not require any specific preparation, but your health care provider may ask you to stop taking certain medications as they may affect the test results. You are strictly advised to consult your doctor about all the medications you are currently taking. It is to be noted, that you should not stop taking any medication without consulting your doctor.
Drugs that can affect T3 levels are as follows:

– Herbal medications.
– Birth control pills
– Antithyroid medications.
– Certain steroids
– Multivitamins and supplements can also affect your test results.

Do I need to fast before a T3 test?

No, there is no need to fast before the T3 test. The test can be done at any time of the day and you can eat or drink normally.

How is the T3 test performed?

Your health professional will collect a sample of blood for the T3 test. The procedure is very simple.

– You will be asked to sit in a comfortable position.

– The technician will then clean an area of your skin in the arm with an antiseptic solution.

– A tourniquet or an elastic band is tied around the arm. This makes the veins to swell up and makes it more visible.

– The technician will find the vein and insert a needle with a vial or a syringe to draw the blood.

– The blood sample will be drawn into the vial or syringe and sent to the laboratory for evaluation.

– After the procedure, the technician will remove the elastic band and put a cotton swab on the spot of injection to prevent bleeding.

How much time does it take to complete the whole procedure?

The procedure will take only a few minutes to complete.

Is the procedure painful?

As the needle is inserted, you will feel slight pain more like a stinging sensation followed by throbbing. The sensation will go away after a short while.

When will I get the results?

You will get the results within a few hours or the next day.

What is the cost of a T3 test in India?

The average cost of a T3 test in India somewhere between INR 300 to INR 500 depending upon the city, laboratory, and quality of the test. The test is often done along with other thyroid tests like T4 and TSH.

What is the normal range of T3?

TypeRange (nanograms per deciliter or ng/dL)
T3 100-200 ng/dL

What do I do after I get my T3 test results?

Normal test results vary according to different laboratories and depend on the age of the patient. After you get your test results, you must seek the advice of your doctor who will explain to you the meaning of your test report.

If your T3 levels are higher or lower than the normal range, it indicates an abnormal test result. if you are pregnant or are suffering from liver disease, you may have high T3 levels.

Your doctor may ask you to do further tests like T4 or TSH to rule out abnormalities or to get a clear opinion of your thyroid functions.

What do abnormal T3 results mean?

Elevated or high T3 levels indicate the following conditions:

Grave’s disease.
– Liver disease.
– A rare condition of T3 thyrotoxicosis
– Toxic nodular goiter.
– Thyroid cancer.

A high level of T3 can also happen during pregnancy especially the first trimester or if you are under any thyroid medication, proteins, supplements, or birth control pills.

A lower than normal T3 range can indicate the following conditions:

– A long-term illness.
– Chronic thyroiditis or Hashimoto disease.

What are the risks of the T3 test?

There are no risks to the T3 test. However, some people may report certain symptoms following the test such as:

– Fainting or lightheadedness.
– Hematoma or accumulation of blood under the skin of the puncture site
– Inflammation of the vein.
– In rare cases, people may experience an infection in and around the site of the skin. In such cases, consult a doctor immediately.

Is it safe for my child to have a T3 test?


Yes, it is completely safe for your child to have a T3 test. For infants, a heel-stick blood test can be done where the blood sample is collected from the heel by inserting a small needle.

The procedure is relatively painless, and parents should accompany their children and make them comfortable. If your child is afraid of needles, help her by explaining the procedure. Ask your technician to help your child to relax before the test. You can try to distract your child by telling her a story or singing a song to your infant.

What are the reference values of T3 for pediatric and young adults?

The below chart shows the reference values for pediatric and young adults under the age of 20.

Pediatric (Age) Range
0 to 5 days 73 to 288 ng/dL
6 days to 2 months 80 to 275 ng/dL
3 to 11 months 86 to 265 ng/dL
1 to 5 years 92 to 248 ng/dL
6 to 10 years 93 to 231 ng/dL
11 to 19 years 91 to 218 ng/dL

Why is the T3 test important during pregnancy?

Thyroid disorders can adversely affect the health of a pregnant woman. During pregnancy, the body goes through a lot of changes especially the thyroid hormones. There are changes in the thyroid hormone levels and it is extremely critical to make accurate assessments of thyroid functions.

Patients who are undergoing a thyroid hormone therapy or needs an alteration in thyroid hormone dose, need to do a T3 test along with other thyroid tests. The thyroid levels vary with the gestational age of the fetus and need to be evaluated regularly for adjusting the thyroid medications.

What are the limitations of the T3 test?

The T3 test is subject to certain limitations such as:

– The T3 test is not conclusive for assessing hypothyroidism.

– Patients need to stop taking multivitamins and dietary supplements 12 hours before the test.

– Certain drugs can produce binding proteins which can affect the free T3 levels.

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