Total T3 blood test in Chiswick
A blood test measuring total T3, the active thyroid hormone in both its bound and free forms, for people with tiredness, weight change or feeling cold, or for monitoring an overactive or treated thyroid.
What the test measures
The thyroid gland produces thyroxine (T4) and a smaller amount of tri-iodothyronine (T3). Much of the T3 in the body is made by converting T4 in tissues such as the liver and kidneys. T3 is the hormone that acts on cells, influencing metabolism, heart rate, body temperature and energy.
Total T3 measures all T3 in the blood, including the large share bound to carrier proteins such as thyroxine-binding globulin. Because carrier protein levels change with pregnancy, oestrogen, illness and some medicines, total T3 can shift even when the active free portion is stable. In practice it is most useful in assessing an overactive thyroid, where T3 can rise before T4.
The price includes the sample taken at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result, and a GP feedback report on request.
Who it is for
- You have symptoms such as weight loss, palpitations, anxiety or heat intolerance and want to discuss an overactive thyroid.
- You have tiredness, weight gain or feel cold and are reviewing thyroid function with a practitioner.
- You are being monitored after treatment for an overactive thyroid.
- You take T3 (liothyronine) or combination thyroid medicine and your doctor would like a level.
- You have already had TSH and free T4 measured and want additional detail.
Understanding your result
Your report shows your total T3 level with the laboratory reference range. A raised level can point towards an overactive thyroid, but it may also reflect higher carrier protein levels, for example in pregnancy or with the contraceptive pill. A low total T3 is common during illness or calorie restriction and does not always mean the thyroid is underactive.
Total T3 is read together with TSH and free T4. A result outside the range is a prompt for discussion with your practitioner and GP, not a diagnosis.
Preparing for your test
There is no need to go without food beforehand. If you take thyroid medicine, have the test before your daily dose unless your doctor advises otherwise. Stop biotin supplements for at least 48 hours, as biotin can interfere with thyroid immunoassays. Tell us if you are pregnant or take oestrogen-containing contraception, HRT, steroids or amiodarone.
For a full view of thyroid function, including TSH, free T4 and free T3, see our thyroid blood tests. If tiredness is the main concern, Tired All The Time looks at several causes. Compare every blood test and price in Chiswick.
Questions
How much is a total T3 test in Chiswick?
The Total T3 test costs £79. The price covers the blood sample at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result, and a GP feedback report on request.
What is the difference between total T3 and free T3?
Total T3 includes hormone bound to proteins and the small free portion. Free T3 measures only the unbound, active hormone and is less affected by changes in carrier proteins.
Can pregnancy affect total T3?
Yes. Higher oestrogen raises carrier proteins, which increases total T3 even when thyroid function is normal.
Is total T3 enough to check my thyroid?
No. TSH is the main first test, with free T4. Total T3 adds detail in particular situations.
