T3, FREE

What are the other names for this test?

Thyroid function test, free triiodothyronine, FT3, Triiodothyronine test, T3 test

What is a T3 (Triiodothyronine) test?

This test determines the amount of T3 (triiodothyronine) in your blood. Your thyroid produces the T3 hormone for your body. A thyroid is a small shaped gland-like butterfly. It is in front of your throat. T4 is another type of hormone known as thyroxine. T3 and T4 provide signals to your body to utilize the energy. T3 is the active type of thyroid hormone, while T4 is the inactive type of thyroid hormone. Your liver converts most of the T4 into the T3 of your thyroid gland. These hormones help to balance many functions of your body, such as
 

• Weight
• Body temperature
• Strength of muscle
• Heart
• Cholesterol level
• Skin moisture
• Breath
• Nervous system
• Bone maintenance
• Growth of brain

What are the two types of T3 hormones?

T3 (Triiodothyronine) are the two types:

Free T3 - When your body needs this type, it comes into your body’s tissues. Free T3 does not combine with protein.

Bound T3 - It combines with proteins that protect it from deposition into the body’s tissues.

Different tests are available that can determine T3 levels. A total T3 test is a blood test that shows both free T3 and bound T3. Free T3 test measures only T3 levels. These tests may use to see the T3 level. If T3 levels are not in the recommended range, it may indicate thyroid disease.

What is the purpose of this test?

A T3 test diagnoses your thyroid conditions, specifically hyperthyroidism, in which your thyroid produces large amounts of thyroid hormones. For most cases, the T3 test performs with T4 and TSH (thyroid-stimulating hormone) tests.

When do I need this test?

Your healthcare provider may recommend this test if you see hyperthyroidism (overactive thyroid). Its symptoms include:
 

• Weight loss
• Difficulty sleeping
• Anxiety
• Increased bowel movements
• Lack of intolerance to heat
• Fatigue
• Changes in the heartbeat
• Shivering in the hands
• Swelling in eyes

Your provider may ask to order T3 tests to observe your T3 levels if you already had experienced thyroid conditions.

What is the procedure for the test?

Your healthcare provider needs a blood sample for a T3 test. A small needle is inserted into a vein in your arm to collect blood into a test tube. Bandage applies to the vein where the needle injects. You can return home for daily activities. This test does not take time greater than five minutes.

How do I need to prepare for the test?

Your provider does not ask for specific preparation for this test. You may need to inform your provider about certain medicines you are using. These medicines may raise or lower your T3 levels.

Is there any risk in the test?

A T3 test has little risk. You may slightly feel the following symptoms at the spot of the vein where the needle injects:
 

• Infection
• Bleeding
• Bruising
• Feeling lightheaded

What do the test results indicate?

The test results depend on the person’s age, gender, medical history, and other factors. Each lab may use different measurement methods.

Many medical conditions can lead to high or low levels of T3. High free T3 levels can indicate that you have hyperthyroidism. It can boost your metabolism, which may be harmful to your health. If you have already been diagnosed with hyperthyroidism, this test helps to identify its severity.

Low T3 levels show that you have hypothyroidism, in which your body does not have the ability to produce recommended thyroid hormone. Your provider compares T3 test results with T4 and TSH tests to see thyroid disease. You can make an online appointment with a doctor to understand your test results at  UmbrellaMD.

What is the recommended range for this test?

The test results in nanograms per deciliter (ng/dL) and picograms per deciliter (pg/dL). The ideal range for total T3 in adults is 80 to 200 ng/dL. The recommended value of free T3 in the blood is 260 to 480 pg/dL. In general, ideal ranges of free T3 for people, such as:
 

• For infants aged between 3 to 30 days old - 1.4 to 5.4 picograms per milliliter (pg/mL)
• For babies 1 month to 1-year-old - 1.5 to 6.4 pg/mL
• For children 1 to 6 years old - 2.0 to 6.0 pg/mL
• For children 7 to 11 years old - 2.7 to 5.2 pg/mL
• For children 12 to 17 years old - 2.3 to 5.0 pg/mL
• For adults 18 to 99 years old - 2.3 to 4.1 pg/mL

What factors may affect the test results?

If you take thyroid hormone medicines or specific medicines like methadone, steroids, or estrogen, it may alter the test results. Intake of an iodine-rich diet can also change your test results.

What else do I need to know about this test?

Your thyroid changes may appear during pregnancy, which is not a big concern. In most cases, T3 may not be recommended for pregnant women. Your provider may suggest this test during pregnancy if you see these
 

• Signs of thyroid disease
• Medical or family history of thyroid disease
• Having autoimmune disease

You can make an online appointment with a doctor at Umbrella Health Care Systems to understand your test results. UmbrellaMD is online healthcare that offers services, including laboratory tests, medical imaging, pharmacies, and e-consultation. Register here to avail the benefits while sitting at home.