Blood test

High T3 level in the blood

Blood test
High T3 level in the blood
Last update: 20/10/2020

What is high level of total T3 (Triiodothyronine) in the blood called?

  • Hypertriiodothyroninemia

What is the normal T3 level in the blood?

If you need to know which are the T3 reference ranges or you require more information about the role of T3 in the blood, you can visit normal T3 level in the blood

What does a high total T3 level in the blood mean?

A T3 (Triiodothyronine) level in the blood higher than normal range may be a sign of hyperthyroidism, a situation that occurs when the thyroid gland produces too much of the thyroid hormones.

T3 values in the blood should be studied along with T4 hormone (thyroxine) and TSH (thyroid-stimulating hormone) values to give a better diagnosis.

There are two types of hyperthyroidism:

  • Primary hyperthyroidism: caused by a problem (hyperfunction) of the thyroid gland. In this case, TSH values will be below the normal range.
  • Secondary hyperthyroidism: caused by a failure of the pituitary gland. In this case TSH values, will be above the normal range.

T3 blood values are usually given in ng/ml but sometimes you can see these values in nmol/l following the International System of Units (SI). In case your values are in nmol/l you can convert them using this tool:


Hypertriiodothyroninemia or high T3 blood levels mean:

  • Marked hypertriiodothyroninemia (> 2 ng/ml in adults):

    Your total T3 blood level is very high and it may be a sign of hyperthyroidism.

    If the TSH (thyroid-stimulating hormone) value is above the normal range is a sign of primary hyperthyroidism. If the TSH value is below the normal range is a sign of secondary hyperthyroidism.

    T3 and TSH are more precise to diagnose hyperthyroidism than T4 (thyroxine) values.

    An additional test of free T3 in the blood can be asked in order to obtain more information about the disorder.

    If your T3 level in the blood is high, you may suffer from palpitations, weight loss, insomnia, irritability or menstrual irregularities.

Which factors can raise the T3 level in the blood?

There are some health circumstances or drugs than can raise your T3 level in the blood:

Which diseases can raise your T3 level in the blood?

The following diseases may raise the T3 level in the blood:

  • Allan–Herndon–Dudley syndrome
  • Toxic multinodular goiter (Plummer's disease)

What can I do to lower the T3 level in the blood?

To reduce the T3 level in the blood you can take, under medical prescription, antithyroid drugs.

Cinnamon intake may help to reduce the level of T3 in the blood.

Where can I find more information about T3 level in the blood?

You can visit our pages about:

Which values are considered a high T3 level in the blood?

The following values are considered to be above the normal range:

IMPORTANT: These levels are expressed in ng/ml. They are an example of a healthy man of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

Marked hypertriiodothyroninemia
2.1 ng/ml2.2 ng/ml2.3 ng/ml2.4 ng/ml2.5 ng/ml2.6 ng/ml2.7 ng/ml2.8 ng/ml
2.9 ng/ml3 ng/ml3.1 ng/ml3.2 ng/ml3.3 ng/ml3.4 ng/ml3.5 ng/ml3.6 ng/ml
3.7 ng/ml3.8 ng/ml3.9 ng/ml4 ng/ml4.1 ng/ml4.2 ng/ml4.3 ng/ml4.4 ng/ml
4.5 ng/ml4.6 ng/ml4.7 ng/ml4.8 ng/ml4.9 ng/ml5 ng/ml5.1 ng/ml5.2 ng/ml
5.3 ng/ml5.4 ng/ml5.5 ng/ml5.6 ng/ml5.7 ng/ml5.8 ng/ml5.9 ng/ml6 ng/ml
Medically reviewed by our Medical staff on 20/10/2020


  • Approved Guideline – Procedures for the Handling and Processing of Blood Specimens, H18-A3. 2004. Clinical and Laboratory Standards Institute.
  • HHS Publication, 6th ed., June 2020. Biosafety in Microbiological and Biomedical Laboratories. Available on:
  • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 783.
  • Tietz. Fundamentals of Clinical Chemistry. Carl A. Burtis, Edward R. Ashwood, David E. Bruns, Barbara G. Sawyer. WB Saunders Company, 2008. Pag 766. ISBN: 978-0-7216-3865-2.
  • Laboratory tests and diagnostic procedures with nursing diagnoses (8th ed), Jane Vincent Corbett, Angela Denise Banks, ISBN: 978-0-13-237332-6, Pag. 400.

Show more

Rating Overview

Share your thoughts about this content

E-mail (Optional):
Add a review