Triiodothyronine Hormone T3 Test
Triiodothyronine Hormone T3 Test is a laboratory test you can order directly. A T3 test measures the amount of triiodothyronine, a thyroid hormone that helps regulate metabolism, in your blood. It is often ordered when a doctor suspects an overactive thyroid or wants to monitor a known thyroid condition.
- Sample type
- blood
- Category
- Hormone
- Turnaround
- 1-3 business days
- Price
- $39
- Referral
- Not required
A T3 test measures the amount of triiodothyronine, a thyroid hormone that helps regulate metabolism, in your blood. It is often ordered when a doctor suspects an overactive thyroid or wants to monitor a known thyroid condition.
What it measures
- Total T3 — Measures all T3 in the blood, including T3 attached to proteins.
- Free T3 — Measures only the unbound T3 that is active and available to body tissues.
- Reverse T3 — An inactive form of T3; sometimes measured in special cases.
Who it is for
Doctors typically order a T3 test for people with symptoms of an overactive thyroid, such as weight loss or a fast heartbeat, or to follow up on abnormal thyroid test results.
Preparation
No fasting is usually required. Tell your doctor about any medicines or supplements you take, as some can affect T3 levels.
Results and what they mean
Results are reported as numbers with a reference range. Your clinician interprets them along with your symptoms and other thyroid tests. This is general information, not medical advice; only your clinician can diagnose or treat a thyroid condition.
How to order this test
- Choose the test and place a confidential order online.
- Select a certified collection site and pick a time that suits you.
- Have your specimen collected — most draws take only a few minutes.
- Review results in a secure portal, typically within 1–3 days.
Preparation, hours, and pricing vary by site; confirm details directly with the lab before your visit.
Availability by state
Direct-access online ordering for the triiodothyronine hormone t3 test is available in most states. It is currently unavailable in 6 states:
Everywhere else you can order confidentially and collect your sample at a certified site. Browse by state →
Frequently asked questions
Do I need to fast for a T3 test?
No, fasting is not typically needed unless your doctor orders other tests at the same time.
What can affect my T3 result?
Medicines like birth control pills, steroids, or thyroid medicines can change T3 levels. Pregnancy can also affect results.
Is a T3 test the same as a T4 test?
No. T3 and T4 are different thyroid hormones. Doctors often order both to get a fuller picture.
How long do results take?
Most T3 tests are ready within 1 to 3 business days.