✍️ Written by the MedTestBD Editorial Team · Last reviewed: July 2026
What is the Free T3 Test?
The Free T3 test measures the amount of triiodothyronine that is unbound and actively circulating in the blood. Unlike total T3, free T3 is not attached to proteins, so it represents the biologically active form of the hormone. It is considered a more precise indicator of thyroid activity than total T3.
Why is the Free T3 Test Done?
- To confirm or rule out hyperthyroidism when TSH is low but Free T4 is normal
- To diagnose T3 toxicosis — a form of hyperthyroidism where only Free T3 is elevated
- To monitor patients on thyroid hormone replacement therapy
- To investigate symptoms such as rapid heartbeat, heat intolerance, tremors, or unexplained weight loss
- To complete a full thyroid panel for a thorough evaluation
Normal Free T3 Levels
| Group | Normal Range |
|---|---|
| Adults | 2.3 – 4.2 pg/mL (3.5 – 6.5 pmol/L) |
| Pregnancy | Slightly lower — interpret with pregnancy-specific ranges |
A high Free T3 alongside a low TSH strongly suggests hyperthyroidism. A low Free T3 may occur in hypothyroidism or in severe non-thyroidal illnesses. Your doctor will interpret results in the context of your full thyroid panel and symptoms.
How to Prepare for the Free T3 Test
- No fasting is required
- If you take thyroid medications, ask your doctor whether to take them before or after the blood draw
- Stop biotin supplements at least 24–48 hours before the test if instructed, as they can falsely alter results
- Inform the lab about any iodine-containing supplements or contrast dye exposure in the recent past
Free T3 Test Price in Bangladesh
Free T3 test prices vary between diagnostic centers across Bangladesh. Compare Free T3 test prices on MedTestBD →
⚠️ This information is for general reference only. Always consult a qualified physician before undergoing any medical test.
