Lab Test Information

What Test Am I Buying?

-T3, Free (Triiodothyronine)

Why Do I Need These?

T3, FreeT3 (triiodothyronine) is one of two major hormones produced by the thyroid, a small, butterfly-shaped gland located at the base of the throat. T3 makes up less than 10% of what we call thyroid hormone, while T4 makes up the rest.

T3, however, is about four times as strong as T4, and is thought to cause most, if not all, the effects of thyroid hormones (80% vs. 20%).The other major thyroid hormone is called T4 (thyroxine). Together they help to control the rate at which the body uses energy.

The T3 test is often carried out as part of an examination when a person has symptoms indicating hyperthyroidism, particularly if the free T4 level is not elevated.

Elevated or reduced levels of thyroid hormone indicate that there is an imbalance between the body's requirements and the supply of hormones, but it does not indicate exactly what is causing this surplus or shortage.

Is Fasting Required?

Fasting is required prior to taking this test. An ideal time to take this test is in the morning.

When Will My Results Be Ready?

Results are typically ready in 7-10 business days or less.


The laboratory services are for informational purposes only. It is not the intention of MYLABFAX LLC to provide specific medical advice but to provide users with information to better understand your health. Please speak to a medical professional about your results for proper diagnosis and treatment. 

Both the physician and the testing laboratory are independent contractors with whom MYLABFAX LLC makes arrangements for your blood tests. By Purchasing your lab tests through MYLABFAX you agree MYLABFAX LLC will NOT be held liable for any acts or omissions of the physicians, the testing laboratory, or their agents or employees.

T3, Free

$ 55.00

Testing not available in: NY, RI, MD and NJ

How Does It Work?

Step 1: Order the lab test.
Step 2: Download and print the lab slip from your login page. 
Step 3: Locate your nearest Quest Diagnostics Laboratory from the 'lab locator' tab on your login page.
Step 4: Visit the laboratory with your slip to have your blood drawn.
Step 5: Results take 7-10 business days. An email will be sent requesting you to login to your page to access them.

For a more detailed explanation, please visit our step-by-step guide on ordering tests.

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