Private thyroid testing
Thyroid blood test
TSH, Free T4, Free T3 and both thyroid antibodies — the full picture rather than TSH alone. A venous sample at a clinic near you, with a written report in 2–5 working days. No GP referral needed.
£114 at a clinic near you
Or £74 as an add-on to an appointment at our Kingston or Crawley clinics.
Why five markers rather than one
Most thyroid testing starts and ends with TSH. For a lot of people that is enough — but it is the signal to the thyroid, not the thyroid itself.
NHS laboratories generally run TSH first and only add Free T4 automatically when the TSH is outside range. That is a sensible way to run a service at national scale, and for straightforward cases it works. What it cannot do is tell you whether your T4 is converting to the active T3 your tissues use, or whether antibodies are present and your thyroid function is likely to drift over the coming years.
Measuring all five at once is most useful if you have symptoms and a TSH that came back normal, if you want to know whether the immune system is involved, or if you are tracking a known thyroid condition and want more than a single number.
What the panel measures
Five markers from a single tube.
Thyroid Stimulating Hormone (TSH)
Made by the pituitary, not the thyroid. It is the signal telling the thyroid to work harder, so it rises when the gland is underperforming and falls when it is overactive. Counter-intuitively, a high TSH usually points to an underactive thyroid.
Free Thyroxine (Free T4)
The main hormone the thyroid actually produces. "Free" means the portion not bound to protein — the part available to your tissues. Read alongside TSH, it separates a thyroid that is struggling from a pituitary that is over-signalling.
Free T3 (Triiodothyronine)
The active hormone. T4 is largely a reservoir that the body converts to T3 where it is needed, so someone can have an acceptable T4 and still be short of the hormone that does the work. This is the marker most often left out of a standard test.
Thyroid Peroxidase (TPO) antibodies
Antibodies against an enzyme the thyroid needs to make hormones. Their presence suggests the immune system is involved, which is the most common reason thyroid function drifts over time in the UK.
Thyroglobulin antibodies
Antibodies against the protein the thyroid stores hormone in. Measured alongside TPO because some people have one and not the other, and testing only one can miss an autoimmune picture entirely.
Before your test
Four things worth knowing. The biotin one catches more people than everything else put together.
Morning is better, but not essential
TSH varies through the day and tends to be highest in the early morning, settling by the afternoon. For a first test it rarely changes the interpretation. If you are re-testing to compare against a previous result, try to book a similar time of day so you are comparing like with like.
Stop biotin supplements for 48 hours
Biotin — vitamin B7, and a common ingredient in hair, skin and nail supplements — interferes with the laboratory method used for thyroid assays and can push results in either direction. It is the single most common avoidable cause of a misleading thyroid result. Stop it two days before, and tell us if you cannot.
No fasting needed
Eat and drink normally. Nothing in this panel is affected by food.
Already on levothyroxine?
Take your dose after the blood draw rather than before, and tell us what you take and when. A sample taken an hour after a dose shows a peak that is not representative of your usual level.
Where you can have it done
At our clinics in Kingston upon Thames and Crawley, or at one of our partner phlebotomy clinics across the UK. Enter your postcode to see what is near you.
Find your nearest location
Enter your postcode to see how far you’d travel.
How testing outside Kingston and Crawley works
- 1Check your postcode above. You will see your three nearest clinics, so you have alternatives if the first is busy.
- 2Get in touch and we will confirm your clinic, take payment and send your referral to the clinic network.
- 3Ring their booking line to arrange a time that suits you. We send you the number and your reference as soon as the referral goes through.
- 4Attend, give your sample, and your written report follows in 2–5 working days.
If we cannot place you, you get your money back.
Appointments are arranged by the clinic, and their availability is not something we control. If none of your nearest clinics can fit you in, tell us and we refund you in full. Please ring to book within 30 days so we are not holding a referral open indefinitely.
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Frequently asked questions
- What does this thyroid blood test include?
- Five markers from one sample: Thyroid Stimulating Hormone (TSH), Free Thyroxine (Free T4), Free T3, thyroid peroxidase (TPO) antibodies and thyroglobulin antibodies. They are read together — TSH on its own cannot distinguish between a thyroid problem and a pituitary one, and antibodies say whether the immune system is involved.
- How is this different from the thyroid test my GP does?
- NHS laboratories usually start with TSH alone and only add Free T4 automatically if the TSH falls outside the reference range. Free T3 and thyroid antibodies are not generally part of a routine check. That is a reasonable way to run a national service at scale, and for most people TSH is enough. This panel measures all five at once, which is more useful if you have symptoms and a normal TSH, or want to know whether antibodies are present.
- Can a blood test diagnose a thyroid condition?
- Thyroid results contribute to a diagnosis but do not make one on their own. Levels shift with illness, pregnancy, medication and time of day, and a single set of numbers is a snapshot rather than a conclusion. Where your results suggest something warrants following up, the report says so plainly and recommends you take it to your GP, who holds your full history and can arrange onward care on the NHS.
- Do I need to stop my supplements before the test?
- Biotin, yes — stop it 48 hours beforehand. Biotin is vitamin B7 and appears in most hair, skin and nail supplements and many B-complex products. It interferes with the laboratory method used for thyroid assays and can shift results in either direction, which is the most common avoidable cause of a misleading thyroid result. Everything else can continue as normal.
- I am already taking levothyroxine. Should I take it before the test?
- Take it after your blood draw rather than before. A sample taken shortly after a dose captures a temporary peak rather than your usual level. Tell us what dose you take and when, so the report reads your results in that context.
- Do I need to fast?
- No. Eat and drink normally — nothing in this panel is affected by food.
- Where can I have the test done?
- At our own clinics in Kingston upon Thames and Crawley, or at one of our partner phlebotomy clinics across the UK. Enter your postcode on this page to see your three nearest options.
- How long do results take?
- Usually 2–5 working days. You receive a written report giving each figure, the reference range it sits against, and a plain-English explanation of what the marker measures and what your result suggests — including where the numbers are genuinely uninformative.
- What if I cannot get an appointment at the clinic?
- Your postcode check shows three nearby clinics, so there is usually an alternative. If none of them can fit you in, tell us and we refund you in full. Appointments are arranged by the clinic and their availability is not something we control, so we would rather give your money back than leave you waiting.
- Is there an age limit?
- This test is for adults aged 18–79.
Book a thyroid blood test
£114 at a clinic near you. Adults 18–79, no GP referral needed, written report in 2–5 working days.