Thyroid function and autoimmune testing
Private thyroid blood test in London
A comprehensive thyroid panel covering TSH, Free T4, Free T3, and TPO antibodies. Designed to identify both common thyroid dysfunction (Hashimoto, Graves, subclinical hypothyroidism) and the autoimmune predisposition often missed by NHS first-line testing. Interpreted by GMC-registered doctors at 134 Harley Street.
Bespoke thyroid panels from £180. NICE CKS aligned.
Quick answer
A comprehensive private thyroid blood test typically covers TSH (thyroid-stimulating hormone), Free T4 (the active thyroid hormone), Free T3 (the most metabolically active thyroid hormone), and TPO antibodies (which identify autoimmune thyroid disease, the commonest UK cause of hypothyroidism). Per NICE CKS Hypothyroidism, a raised TSH with low Free T4 supports a diagnosis of primary hypothyroidism; subclinical disease shows raised TSH with normal Free T4; central pituitary causes show low TSH and low Free T4 together. WMG Health bespoke thyroid panels from £180. Same-day appointments at 134 Harley Street, London W1G 7JY.
When a thyroid blood test is most useful
- Persistent fatigue, weight gain, or cold intolerance. The classic hypothyroid pattern. Many NHS bloods only test TSH; private testing adds Free T4 and TPO antibodies for the full picture.
- Unintentional weight loss, palpitations, heat intolerance, or anxiety. The classic hyperthyroid pattern. Free T3 is particularly informative here, especially in suspected Graves disease where T3-predominant hyperthyroidism can occur.
- Hair shedding or diffuse hair loss. Both hypothyroidism and hyperthyroidism are recognised causes of telogen effluvium. Thyroid bloods are typically done alongside iron studies, vitamin D and B12 in a hair-focused workup.
- NHS TSH "normal" but symptoms persist. A common reason for booking with us. We add Free T4, Free T3 and TPO antibodies to surface what NHS reflex testing may have missed (subclinical disease, autoimmune predisposition, peripheral conversion issues).
- Pre-conception or fertility planning. Untreated hypothyroidism increases miscarriage and preterm risk; even subclinical disease may matter. A thyroid baseline is sensible 3 to 6 months before trying to conceive.
- Family history of autoimmune thyroid disease. Hashimoto thyroiditis and Graves disease cluster in families. TPO antibodies surface predisposition before overt disease develops.
- Already on levothyroxine and wanting a defensible review baseline. Comprehensive bloods support a conversation with your GP or endocrinologist about dose adjustment.
What is measured
A comprehensive thyroid panel. Your final markers are confirmed by a GMC-registered doctor before booking.
TSH (thyroid-stimulating hormone)
The first-line marker of thyroid function. According to NICE CKS Hypothyroidism, the typical adult reference range is approximately 0.27 to 4.2 mIU/L on the Roche Elecsys assay used widely in UK labs. A raised TSH usually points to an underactive thyroid (hypothyroidism); a suppressed TSH to an overactive thyroid (hyperthyroidism).
Free T4 (free thyroxine)
The unbound, biologically active form of thyroxine, the main hormone the thyroid releases. Tested alongside TSH because the pair tells you whether the problem is the thyroid itself (primary disease) or the pituitary signal (central disease). Typical adult range 12 to 22 pmol/L on Roche Elecsys.
Free T3 (free triiodothyronine)
The biologically active thyroid hormone tissues actually use. Useful when TSH and Free T4 disagree, in suspected T3-predominant hyperthyroidism (sometimes seen in Graves disease), and for monitoring some thyroid hormone replacement regimens.
TPO antibodies (thyroid peroxidase)
Identifies autoimmune thyroid disease, the commonest UK cause of hypothyroidism (Hashimoto thyroiditis). A positive TPO with raised TSH supports a clinical diagnosis of autoimmune hypothyroidism and predicts progression risk in subclinical cases (around 2 to 4 percent per year if TPO-positive).
Thyroglobulin antibodies (optional add-on)
A second autoimmune marker. Adds sensitivity to autoimmune thyroid disease detection where TPO is borderline or negative but clinical suspicion persists. Available as a bespoke panel add-on.
How your results will read
The thyroid axis is a feedback loop, so the combination of markers tells you what is happening. The interpretation patterns our doctors use:
High TSH + Low Free T4
Primary hypothyroidism. The thyroid is failing; the pituitary is driving TSH up in compensation. Add TPO antibodies to identify Hashimoto as the cause (commonest UK aetiology). Treatment is levothyroxine, prescribed and monitored by NHS GP or endocrinologist.
High TSH + Normal Free T4
Subclinical hypothyroidism. Often asymptomatic but progressing toward overt disease, particularly if TPO antibodies are positive (around 2 to 4 percent annual progression risk). Annual TSH monitoring per NICE CKS, treatment decisions individualised.
Low TSH + High Free T4 or Free T3
Primary hyperthyroidism. Add TSH receptor antibodies (TRAb) to confirm Graves disease. Endocrinology referral per NICE CKS Hyperthyroidism. T3-predominant hyperthyroidism is recognised in some Graves cases, which is why Free T3 matters.
Low TSH + Low Free T4
Central (pituitary) hypothyroidism, rare but important. Or sick euthyroid syndrome during acute illness. Pituitary work-up indicated: morning cortisol, prolactin, FSH and LH, IGF-1.
Normal TSH and Free T4 + Positive TPO antibodies
Euthyroid autoimmune thyroid disease, biochemically normal now but at meaningfully raised risk of progression to overt disease within a few years. Annual TSH monitoring recommended.
What happens if your results are abnormal
WMG Health provides the diagnostic workup and clinical interpretation. If your results suggest hypothyroidism, hyperthyroidism, or autoimmune thyroid disease, your doctor will produce a written report you can take to your GP or an NHS endocrinologist for treatment, which for hypothyroidism is typically levothyroxine prescribed and monitored on the NHS pathway under NICE CKS Hypothyroidism.
For hyperthyroidism, the NHS pathway is via endocrinology referral for confirmation (TRAb antibodies, thyroid uptake scanning where indicated) and management. For autoimmune thyroid disease without overt biochemical disease (positive TPO antibodies, normal TSH), the recommendation is typically annual monitoring.
If thyroid bloods are normal but your symptoms persist, we will look at other explanations: iron studies for fatigue and hair shedding, vitamin D and B12 for low mood and brain fog, female hormone axis for perimenopause-mimicking symptoms, adrenal markers (cortisol, DHEA-sulfate) for stress-related presentations. A bespoke custom panel is often the right next step.
Symptoms commonly investigated alongside thyroid bloods
If you are not sure whether thyroid testing is right for your case, the symptom guides below explain the typical presentations and the testing pathway each follows.
Read about each thyroid marker individually
Each marker in the panel has its own reference page explaining what it measures, its UK reference range, and what high or low values typically mean.
FAQs
Should I get a thyroid blood test if my GP test came back "normal"?
Many NHS thyroid screens measure TSH alone, with reflex testing of Free T4 only if TSH is abnormal. Private testing typically adds Free T4, Free T3 and TPO antibodies up front. The fuller picture can distinguish primary thyroid disease (high TSH, low Free T4), subclinical hypothyroidism (high TSH, normal Free T4), central pituitary causes (low TSH and low Free T4 together), and autoimmune predisposition (TPO antibodies positive). Many patients with "normal" NHS TSH come back with raised TPO antibodies, which puts them at significantly higher risk of overt hypothyroidism within a few years.
What symptoms suggest an underactive or overactive thyroid?
Hypothyroidism (underactive) typically presents with fatigue, weight gain despite no change in diet, cold intolerance, dry skin, hair shedding or thinning, constipation, low mood, brain fog, and menstrual changes. Hyperthyroidism (overactive) typically presents with unintentional weight loss, heat intolerance, palpitations, anxiety, tremor, frequent loose stools, and (in Graves disease) eye changes. These symptoms overlap with many other conditions, including perimenopause, anaemia, and chronic stress, which is why bloods are the definitive next step.
How much does a private thyroid blood test cost?
Our Hormone Specialist panel (£299) includes TSH, Free T4, Free T3 and a comprehensive endocrine workup. The General Wellness panel (£279) includes TSH and Free T4 as part of a broader baseline. A bespoke thyroid-only panel built around your specific question (for example TSH + Free T4 + Free T3 + TPO antibodies) typically lands in the £180 to £260 range. We confirm the exact price in writing before booking.
How quickly will I get results?
TSH and Free T4 are clinician-reviewed within 4 hours of your appointment. Free T3 typically by end of the same working day. TPO antibodies and thyroglobulin antibodies take up to 48 hours. Every result is interpreted against your symptoms and history by a GMC-registered doctor and released through our secure patient portal with a written report.
If results show hypothyroidism, what happens next?
Treatment for confirmed primary hypothyroidism is levothyroxine, prescribed and monitored by an NHS GP or endocrinologist under NICE CKS Hypothyroidism. WMG Health provides the diagnostic workup and clinical interpretation; we will produce a written report you can share with your GP or specialist to initiate treatment. We do not prescribe thyroid hormone replacement directly. For hyperthyroidism or autoimmune thyroid disease, the same referral pathway applies.
Do I need to fast before a thyroid blood test?
An overnight fast (8 to 12 hours, water only) gives the cleanest Free T4 reading and is recommended. TSH varies through the day and tends to be highest in the early morning, so an 8 to 10 AM appointment is ideal. If you take levothyroxine, take it AFTER your blood draw (not before) to avoid an artificially high Free T4 result. Biotin supplements at high dose interfere with both TSH and Free T4 immunoassays, so hold biotin or B-complex supplements for 48 to 72 hours before testing.
Can thyroid problems explain my hair loss?
Yes. Both hypothyroidism and hyperthyroidism are well-recognised causes of diffuse hair shedding (telogen effluvium), and untreated thyroid disease can also alter hair texture and slow regrowth. Hair shedding is rarely caused by thyroid alone, so a hair-focused workup typically also covers ferritin (iron stores), vitamin D, vitamin B12, and the hormonal axis. Our Hair Loss Essentials and Advanced Hair & Hormone Check panels are designed for this.
Ready to book?
Same-day appointments at 134 Harley Street usually available. A GMC-registered doctor confirms your panel and exact price within 1 working day.
From £180 · NICE CKS aligned · Confirmed within 1 working day