Total Thyroxine (T4)

Total T4 alongside free T4. Rarely offered in UK direct-to-consumer testing.

Add-on markers can only be added to venous samples.

Timing

Take in the morning, ideally fasted, alongside the rest of thyroid function. If you take levothyroxine, take the sample before that day’s dose. A dose taken a few hours earlier lifts T4.

Ideal, not required. Glucose is the only marker we sell that is invalid unfasted. If fasting does not fit your day, take it anyway and do the same next time.

Turnaround: the lab reports this test within 24 hours of receiving your sample, counted in working days. Most samples reach them within about 3 days of posting. Full detail on our Turnaround Times page.

We do not interpret results. Not medical advice or a diagnosis.