Lab test · Endocrinology
Free Triiodothyronine (Free T3)
Thyroid function
- Blood sample
- No fasting
- Report within 24 hours
- Home collection
What this test is for
Thyroid function
Free T3 measures triiodothyronine, the most active thyroid hormone, in its unbound form that can act on the body's cells. Much of the body's T3 is made from T4 in the tissues rather than by the thyroid itself. Free T3 is used mainly to check for or follow an overactive thyroid, and is usually read with TSH and free T4.
Why a doctor may order it
- To look for an overactive thyroid when TSH is low but free T4 is normal
- To check symptoms such as weight loss, palpitations, anxiety, heat intolerance or shaky hands
- To monitor treatment for an overactive thyroid, including Graves' disease
- As part of a full thyroid profile together with TSH and free T4
How to prepare
Fasting: Not needed.
Eat and drink as usual; fasting is not required. If you take biotin supplements or a multivitamin that contains biotin, let your doctor know, as biotin can interfere with thyroid hormone tests. Continue your regular medicines unless your doctor has told you otherwise.
At home
- Sample
- Blood sample
- How it works
- During the home visit, the collector draws a small tube of blood from a vein in your arm. It takes a few minutes, and free T3, free T4 and TSH can usually all be measured from the same sample.
- Report
- Within 24 hours of collection.
What the results can mean
Your report shows free T3 beside the laboratory's reference range. A high free T3, particularly with a low TSH, can point to an overactive thyroid. A low free T3 is less useful on its own, because it can fall during any serious illness or poor nutrition even when the thyroid is healthy. Your doctor will interpret free T3 together with TSH, free T4 and your symptoms.
What's included
One test: Free Triiodothyronine (Free T3), from one blood sample.
Related tests
- Free Thyroxine (Free T4)Thyroid function৳500
- Thyroid Stimulating Hormone (TSH)TSH is a hormone made by the pituitary gland at the base of the brain.
- Free Thyroid Profile (FT3, FT4, TSH)This profile measures three thyroid tests from one blood sample: TSH, the pituitary hormone that controls the thyroid, and the free forms of the two thyroid hormones, T4 and T3.
- TSH Receptor Antibodies (TRAb)Graves' disease (overactive thyroid)৳2,350
- Thyroid Function Test (T3, T4, TSH)A thyroid function test measures TSH, the pituitary hormone that controls the thyroid, together with the thyroid hormones T3 and T4.
Questions people ask
Is free T3 needed to check for an underactive thyroid?
Usually not. TSH and free T4 are the main tests for an underactive thyroid, because free T3 often stays normal until late. Free T3 is more useful when an overactive thyroid is suspected.
What is the difference between T3 and free T3?
Total T3 includes hormone bound to blood proteins as well as the free part. Free T3 measures only the unbound, active hormone, so it is less affected by changes in those proteins.
Can illness change T3 levels?
Yes. During serious illness, after surgery or with poor nutrition, the body makes less T3 from T4, so free T3 can be low even if the thyroid is healthy.
What does a high free T3 mean?
A high free T3 usually suggests an overactive thyroid, especially when TSH is low. Your doctor may order more tests, such as TSH receptor antibodies, to find the cause.
How much does a Free T3 test cost in Dhaka?
With Mukti Health the price is ৳500, and the sample is collected at your home in Dhaka. You see the price again before you confirm the booking in the Mukti Health app.
Can I do the Free T3 test at home in Dhaka?
Yes. Book it in the Mukti Health app and a trained sample collector comes to your home in Dhaka to take the blood sample. You do not need to go to a laboratory.
How long does the Free T3 report take?
The report is usually ready within 24 hours of the sample being collected.