Knowledge Centre
Providing rapid medical guidance and expert health insights for informational purposes. Our guides come from a Harley Street clinic, but they do not replace a professional consultation.
Thyroid Symptoms: Which Blood Test Do You Need?
Written by Mr Stephen Lingam · Reviewed by Dr Mohammad Bakhtiar (GMC 4694470) on 01/10/2026
Key takeaways
- Tiredness, weight change, feeling cold or anxious, and changes to mood or periods can all have a thyroid cause, alongside many other explanations.
- Thyroid Profile 1 (TSH and free T4) is the standard first test: £100 plus the £50 phlebotomy fee, usually back in 1 working day.
- Thyroid Profile 3 adds free T3 (£142.50); Thyroid Profile 2 adds antibodies (£238.75), and the antibody panel may take 2 working days.
- A private GP consultation (£150) can help you choose which profile fits your symptoms, and go through the result with you afterwards.
- Thyroid and perimenopause symptoms overlap, so some patients are better served starting with a broader hormone panel.
- Walk-in testing is available 7 days a week at 117a Harley Street.
Tiredness, weight gain, feeling cold, low mood or a fast heartbeat can all have a thyroid cause, but each of these has many other causes too. A thyroid blood test measuring TSH and free T4 is the usual starting point, with results back in around a working day at our clinic.
Underactive vs overactive thyroid symptoms
An underactive thyroid tends to show as tiredness, weight gain, feeling cold, low mood, dry skin or constipation. An overactive thyroid tends to show as weight loss, feeling hot, anxiety, a fast or irregular heartbeat, tremor or trouble sleeping. Both lists overlap with many other conditions, which is why a blood test, not a symptom list, tells them apart.
| Underactive thyroid | Overactive thyroid |
|---|---|
| Tiredness | Weight loss |
| Weight gain | Feeling hot |
| Feeling cold | Anxiety or feeling on edge |
| Low mood | Fast or irregular heartbeat |
| Dry skin | Tremor |
| Constipation | Trouble sleeping |
These symptoms have many possible causes. If tiredness on its own is your main concern, our guide to feeling tired all the time or a fatigue assessment can be a better starting point than thyroid testing alone.
Which thyroid blood test to book
Most people start with Thyroid Profile 1, which measures TSH and free T4 for £100 plus the £50 phlebotomy fee, usually back in 1 working day. Profile 3 adds free T3, and Profile 2 adds thyroid antibodies for a broader picture. All three are booked the same way, walk-in or online, 7 days a week.
| Profile | Includes | Price | Turnaround |
|---|---|---|---|
| Thyroid Profile 1 | Free T4, TSH | £100 | Usually 1 working day |
| Thyroid Profile 3 | Free T3, Free T4, TSH | £142.50 | Usually 1 working day |
| Thyroid Profile 2 | T4, TSH, Free T3, Free T4, thyroglobulin antibodies, TPO antibodies | £238.75 | Usually 1 working day; the antibody panel may take 2 working days |
Every price is plus the £50 phlebotomy fee for the blood draw. Visit the thyroid function test page to compare all three profiles and book.
When to add antibodies or T3
Free T3, included in Profile 3, is added when that extra hormone reading is clinically relevant to your symptoms. Thyroid antibodies, included in Profile 2, are added when autoimmune thyroid disease is being considered, for example alongside a family history of thyroid problems. Neither is needed for a routine first check; TSH and free T4 usually come first.
Booking a broader profile straight away isn't wrong, but it isn't automatically the better choice either. Many people are well served by Profile 1 first, then a wider profile only if the result or their symptoms point that way.
Thyroid or menopause?
Thyroid symptoms and perimenopause symptoms overlap: both can cause tiredness, low mood, weight change and disturbed sleep. Where periods are also changing, or symptoms started around the usual age for perimenopause, a broader hormone picture can be more useful than thyroid testing on its own.
Our menopause blood test covers a wider hormone panel for exactly this overlap, so it's worth considering alongside, or instead of, a standalone thyroid profile.
When to see a GP rather than just test
A blood test on its own gives a result, not a diagnosis. It's worth seeing a doctor first if you're not sure which profile fits your symptoms, if you have other symptoms alongside the tiredness or weight change, or if you'd rather have the result explained the same week it arrives.
A private GP consultation is £150 and can help you choose the right profile before testing, or go through the result with you once it's back. Our guide to an abnormal result GP review explains what that follow-up involves.
Preparing for the test
No special preparation is required for a standard thyroid blood test. Tell the clinic about any thyroid medicine you take and any biotin supplements, since these can affect some laboratory results. Book online or walk in at 117a Harley Street, 7 days a week, alongside any of our other private blood tests in London.
If you already have a TSH result and want to know what the number means, Blood London's guide explains what your TSH result means.
Mr Stephen Lingam
Managing Director
Executive leadership
Frequently asked questions
What is the best blood test for thyroid problems?
TSH and free T4, in Thyroid Profile 1 (£100 plus the £50 phlebotomy fee), is the standard first check. Free T3 or thyroid antibodies are added if there's a specific reason to look further.
Can thyroid problems cause anxiety?
Yes, anxiety and feeling on edge can be part of an overactive thyroid picture, though anxiety has many other causes too. A blood test helps separate a thyroid cause from the others.
Do I need to fast?
No special fast is required for thyroid testing. Tell the clinic about any thyroid medicine or biotin supplements before your sample is taken.
How quickly are results back?
Thyroid Profile 1 and Profile 3 are usually back in 1 working day; Thyroid Profile 2's antibody panel may take 2 working days. The turnaround clock starts when your sample reaches the lab, which happens the same day, including weekend samples.
Can a normal result rule out thyroid disease?
Not entirely on its own. A single normal TSH and free T4 result is reassuring, but symptoms that continue are worth discussing with a doctor, who can decide whether a broader profile or a repeat test is useful.
Will the GP explain my results?
Yes. A private GP consultation (£150) goes through your result alongside your symptoms and history, and agrees the next step, including whether repeat testing or further investigation is worthwhile.
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