Triiodothryronine-Free

What Does This Test Check?

Free T3 is the most active thyroid hormone, converted from T4 in the body's tissues. It is checked when thyroid results and symptoms do not line up neatly.

Lola Health lists this as an add-on biomarker at £12, posted as a home sample with results in one to four working days. It cannot be bought on its own: you pick it while ordering one of Lola's main blood tests, so it suits someone who already knows which extra marker they want.

An abnormal level may indicate a thyroid imbalance, but T3 alone is rarely decisive and the full TSH, T4, T3 set is read together. Testing needs a clear reason. Whatever the reading, an out-of-range result needs a doctor who can see the whole picture, so go through it with your GP before acting on it.