T3 (triiodothyronine) total test
Quick answer: A total T3 test measures triiodothyronine, one of the main thyroid hormones, in your blood. It is ordered with TSH and T4 when an overactive thyroid is suspected or to monitor thyroid treatment.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed.
- In fertility careThyroid problems can affect periods, ovulation and pregnancy, so thyroid tests are common in fertility care.
How the test is done
- 1You sit down and the skin over a vein is cleaned
- 2Blood is drawn into a tube, often in the same sample as TSH and T4
- 3A plaster is applied
- 4The lab measures total T3 in the sample
What your results can mean
Reading your report
Pregnancy and some medicines change total T3 levels, so read it with your TSH and discuss it with your doctor.
If the result is outside the usual range
A high total T3 can be seen with an overactive thyroid, pregnancy or oestrogen medicines. A low total T3 can be seen with an underactive thyroid, but also commonly during serious illness, fasting or with some medicines.
Who usually has this test
People with symptoms of an overactive thyroid, such as weight loss, a racing heart or tremor, and people on thyroid treatment.
Risks and aftercare
You can leave right after the sample, with only a small plaster on your arm.
Names and options
Also called: total T3, T3 test
Listed by the hospital as
- T3 (TRIIODOTHYRONINE) TOTAL, SERUM
Questions about this test
What is the difference between total T3 and free T3?
Total T3 measures all T3 in the blood, including the part bound to proteins. Free T3 measures only the active, unbound part. Pregnancy and hormone medicines change total T3 more than free T3.
Why is T3 tested if TSH is normal?
Usually it is not needed. T3 is mostly checked when TSH is low, to look for an overactive thyroid, or when symptoms do not match the TSH result.
Can illness lower T3?
Yes. Serious illness, fasting or surgery can lower T3 for a while even when the thyroid is healthy. Doctors usually recheck once you have recovered.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
Get directions ↗IVF Pulse fertility care at Tamara Hospital →
Reception
Waiting area
IVF lab
This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.