ft3 (eclia)
ThyroidBlood sampleResults 24 hrsNo fasting
FT3 (ECLIA)
FT3 (Free Triiodothyronine) measures the active, unbound form of the T3 hormone available to your body's tissues. It is often used to help confirm or assess hyperthyroidism, where FT3 may be elevated, and to fine-tune thyroid evaluation alongside TSH and FT4.
Sample
Blood
Results
24 hrs
Fasting
Not required
Follow-up
Optional add-on
What this test detects
Free T3 (FT3)
ECLIA · serum
Quantitative (pg/mL)
When to get this test
Suspected hyperthyroidism
Helps confirm an overactive thyroid, where free T3 is often raised.
Clarifying abnormal thyroid results
Useful when TSH or FT4 results are unclear and more detail on active hormone is needed.
Symptoms of an overactive thyroid
Supports evaluation of palpitations, tremors, weight loss, or heat intolerance.
How to prepare
01
No special preparation needed.
02
If you take thyroid medication, ask whether to take it before or after the draw.
Common questions
Do I need to fast before an FT3 test?
No, fasting is not required. You may eat and drink normally before your blood draw.
What is the difference between FT3 and TSH?
TSH is the signal that controls the thyroid, while FT3 measures the active form of T3 hormone available to your tissues. Doctors use them together to assess thyroid function more precisely.
How is FT3 different from total T3?
FT3 measures only the free, unbound hormone that is biologically active, while total T3 includes hormone bound to proteins in the blood. FT3 can give a clearer view in certain situations.