Thyroid Function

TSH with both free hormones — not TSH on its own.

Markers measured (3)

• TSH
• Free T3
• Free T4

Timing

Take in the morning, ideally fasted. TSH is at its highest overnight and drifts down through the day, and it reads a little higher fasted than after food. Fixing the time is what makes this test comparable with the next one.

If you take levothyroxine, take the sample before that day’s dose. A dose taken a few hours earlier lifts free 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.

Venous or finger prick

Same markers either way.

Venous — a professional takes the sample. You choose one of the four blood draw options in your basket, before checkout. Book Monday to Thursday and post the same day.
Finger prick — an at-home test you do yourself, in under ten minutes. No blood draw appointment needed. Post it the same day it is taken. The timing above still applies. Collect Monday to Thursday and post the same day. Finger-prick samples fail more often than venous ones; what that means.

Before you order

• How it works — the four blood draw options, what each costs, and the process end to end.
• Choosing a test — what to check before buying any blood test, here or anywhere.
• Biomarker Guide — every marker we run, in plain English.
• Body Guide — what each organ and system actually does.

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.