Thyroid: what is T3 and it’s ideal levels.

Overview of T3 test

The thyroid gland is located in the middle of the neck, which lies just below Adam’s apple. The thyroid gland is responsible for the production of hormones and it also controls utilization of energy by the body as well as body sensitivity against other hormones.

T3 or Triiodothyronine is one of the thyroid hormones which play a crucial role in controlling the metabolic rate of the body. Besides this, it also affects the several digestive functions, muscle control, bone maintenance, heart functioning, and brain development and function.

T3 is the active form of thyroxine which is another thyroid hormone. Nearly 20% of triiodothyronine secretion occurs directly by the thyroid gland into the bloodstream. The remaining 80% is formed by the conversion of thyroxine into triiodothyronine by the organs like liver and kidneys.

Most of the formed T3 hormone in the body tends to bind to the protein. However, the remaining which does not bind remains free-floating in the blood. The most commonly performed test is of T3 total test which measures both the kinds of bound and unbound T3 levels in the blood.

Your physician can determine the type of thyroid problem you might be experiencing by knowing your T3 levels.

T3  Test

Does too much of triiodothyronine cause some problems?

If you have too much of thyroid hormone in your bloodstream then you are probably experiencing from thyrotoxicosis. It might be recognized by goiter, in which enlarged thyroid causes swelling around the neck. It might be because of hyperthyroidism or overactive thyroid which is caused by Graves’ disease or inflammation of the thyroid gland or presence of some benign tumor in the thyroid.

Few other symptoms of thyrotoxicosis might include weight loss, heat intolerance, increase in appetite, irregular menstrual cycles, increase in bowel movements, palpitations or irregular heartbeat, extreme tiredness, tremors, irritability, hair loss or thinning, and eyelids retraction which causes a “staring appearance”.

What can happen if there is too little of triiodothyronine?


Too less production of triiodothyronine leads to hypothyroidism. It might happen because of some autoimmune disorder like Hashimoto’s disease, o simple because of poor iodine intake. This kind of condition might even lead to a learning disability or reduced growth before birth or during childhood. In adults, it might show symptoms of depression, poor memory, etc.

Why should I undergo T3 tests?

Your physician might suggest you take a T3 test. If he suspects you have any probable symptoms of:

  • Hyperthyroidism or there appears chances your body is producing an excess of thyroid hormone
  • Hypopituitarism or your pituitary gland seems to be making an abnormal amount of hormone
  • Primary or secondary hypothyroidism
  • Thyrotoxic periodic paralysis or your thyroid appears to be producing high amounts of thyroid hormones which results in muscle weakness

Any thyroid disorder might show a wide range of symptoms like certain mental issues of anxiety, menstrual irregularities, constipation, sleeping disorder, weakness, sudden weight changes, increased sensitivity towards hot or cold, skin problems like puffiness or dryness, palpitations, dryness or puffiness in eyes, and hand tremors etc.

If you already have a confirmation about a thyroid problem, then your physician might want you to repeat the T3 test to observe any significant changes in the values.

How to prepare for a T3 test?

Some medications like steroids, thyroid pills, birth control pills, and other hormonal pills might affect the T3 test results. So it is important to discuss with your doctor about all the medications you are taking prior undergoing the test. Your doctor might even suggest temporarily stop taking those meds just to avoid its effect on the results.

What is the procedure of a T3 Test?

This test involves blood sample withdrawal which is then sent for evaluation in the laboratory. You might experience a little bit of discomfort while the blood sample is being collected. However, it involves no risk except just a little bruise or minor bleeding afterward along with light-headedness in some cases. Serious symptoms like fainting, excessive bleeding, and vein inflammation are rare to happen.

How to understand T3 test results better?

The functioning of the thyroid gland is complicated and a single test might not give a clear view of any thyroid functioning. However, abnormal values of T3 levels might help your physician to trace a problem moving in the right direction. Few more thyroid tests can be recommended by your physician. Usually, the result of the test ranges between 100 to 200 ng/dL in case of normal results.

Also, abnormally high values of T3 are very common to appear in case of pregnant women and the ones with any kind of liver disease. So the free T3 level measurement in the T3 test might help your physician to rule out these conditions certainly.

High T3 levels:

If you are not pregnant or suffering from any liver disease then increase your T3 levels might indicate following thyroid problem like:

  • Hyperthyroidism
  • Toxic nodular goiter
  • Thyrotoxic periodic paralysis
  • Graves’ disease
  • Painless or silent thyroiditis

T3 Test

  • High protein levels in the blood also indicate high T3 levels at times
  • In extreme cases thyroid cancer or thyrotoxicosis

Low T3 levels:

Abnormally low T3 levels might indicate towards hypothyroidism condition or even starvation. It might also indicate a long-term illness because T3 levels gradually tend to decrease if you’re sick. This can also be a reason why doctors do not prefer test for T3 levels as the only affirmation test of thyroid functioning. Instead, they recommend T3, T4, and TSH altogether to get a clearer view of thyroid.


It is always necessary to catch hold of any disease before it raises alarming complications. So do not wait until your body alarms towards several complicated diseases and get a Thyroid Test now. Also, getting normal results for a T3 test does not simply indicate that the thyroid functioning is perfect. Further evaluation of T4 and TSH can give a clearer picture if there is any thyroid malfunctioning or not.

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