Quick Navigation


T3, or triiodothyronine, is one of the two circulating Thyroid Hormones and is the more metabolically active one (relative to T4). Used as therapy for hypothyroidics, T3 may hold some promise as being a short-term fat burner and cognitive enhancer vicariously through the effects of thyroid hormones.

Our evidence-based analysis on t3 features 26 unique references to scientific papers.

Research analysis led by and reviewed by the Examine team.
Last Updated:

Summary of T3

Primary information, health benefits, side effects, usage, and other important details

T3 is one of the two biologically active thyroid hormones, the other being T4. T3 is seen as more potent although less prominent in the body, and T4 can act as a reservoir of potential T3, to be converted into the more potent form through a class of enzymes known as deiodinases.

Guidance from the experts

Learn what supplements to take for your specific health goals with the Examine Supplement Guides.

Want a deeper look at the research? Examine Members get full access to the comprehensive research database, monthly study summaries, and the latest in-depth analysis.

Your support allows us to be 100% independent and unbiased.

How to Take

Recommended dosage, active amounts, other details

Studies done in humans with T3 supplementation have been done with ranging dosages of 40mcg daily up to 150mcg daily.

Doses tend to be taken every 8 hours, which ends up being three times daily in even intervals.

The related compound T4, when taken fasted rather than during meals, may result in higher blood levels of T4 and less of a spike in TSH.[1] Additionally, taking a dose before bed seems to cause a greater increase relative to a dose before meals.[2] One study does note that despite these higher C^max values, that overall there really isn't a huge difference in treatment.[3]

Things to Note

Is a Form Of

Primary Function:

Other Functions:

Also Known As

Triiodothyronine, Liothyronine

Do Not Confuse With

Thyroxine (T4)

Caution Notice

Overdosing of T3 and/or T4 can lead to symptoms of hyperthyroidism, which range far wider than just the metabolic rate. Caution should be taken in not overdosing T3/T4 in either acute dosage or duration.

  • T3 supplementation, although a fat burner, is non-stimulatory (in the classical sense, like caffeine)

Get our free 5-day course on the essentials of supplementation.

At Examine, our incentives line up with yours — getting unbiased information. That's why we don’t sell any advertising or supplements.

Join over 250,000 people who have learned about effective versus overrated supplements, tips for buying supplements, and how to combine supplements for safety and efficacy.

Click here to see all 26 references.