Symptom · Night sweats
Waking drenched, changing the sheets, sleeping on a towel. In women over 40 the answer is usually falling oestradiol, and it arrives long before periods stop. In men and younger women the list is shorter and more varied: an overactive thyroid, low testosterone, an overnight blood sugar dip, a low-grade infection or inflammation, alcohol, or a medication you started. A blood panel separates these in one draw. It also does something more important: it checks the markers that would point to something serious, so that if they are clean you can stop worrying and treat the cause.
Venous draw at 103 UK clinics or at home. Morning appointment for hormones and cortisol. Report within 48 hours of the lab receiving your sample.
Last reviewed 16 September 2026
The short answer
A blood test for night sweats should cover oestradiol and FSH (women), testosterone and SHBG (men), a full thyroid panel, HbA1c with fasting insulin, hs-CRP and a full blood count, and morning cortisol. In a woman between 40 and 55 with irregular periods, the answer is perimenopause the large majority of the time and the panel mostly confirms it and rules out the thyroid. In anyone else, and particularly in a man, night sweats without an obvious cause deserve a proper look, because the list includes things that need treating.
See a GP this week, not a blood panel, if
Your night sweats come with unexplained weight loss, fevers, a lump or swollen gland that has not gone, a persistent cough, or you have recently travelled somewhere with tuberculosis or malaria. Drenching night sweats with those features can point to infection or lymphoma, and they need a doctor's examination, not a private test. A panel is the right first step when night sweats are the only symptom.
What to test
| Marker | What it points to | What to look for | What happens next | Panel |
|---|---|---|---|---|
| Oestradiol and FSH (women) | Perimenopause. Falling oestrogen destabilises the brain's temperature control, which is what a hot flush is | FSH rising above 25 IU/L with a low oestradiol, particularly on day 2 to 5 of a cycle. Levels swing week to week, so one reading is a clue, not a verdict | HRT is effective and available from a GP; the result helps the conversation, especially under 45 | Core hormones in Advanced; complete set in Ultimate and Signature |
| Thyroid (TSH, free T4, free T3, antibodies) | An overactive thyroid raises the metabolic rate: night sweats, heat intolerance, palpitations, weight loss, anxiety, early waking | TSH below 0.4 with a raised free T4 or free T3; positive antibodies | GP referral; treatment resolves the sweats entirely | All panels |
| Testosterone and SHBG (men) | Low testosterone causes night sweats and hot flushes in men, exactly as low oestrogen does in women. Common after 50, and the standard explanation nobody offers | Total testosterone in the bottom quarter on a morning sample; high SHBG lowering the free fraction | GP or a men's health clinic; two morning readings are needed before treatment | Testosterone in Advanced; SHBG and free testosterone in Ultimate and Signature |
| HbA1c, fasting insulin, HOMA-IR | An overnight glucose dip triggers adrenaline: you wake sweating, often at 3 to 4am, sometimes hungry or shaky. Most common in people on diabetes medication, but insulin resistance alone does it | HbA1c above 38 with symptoms; fasting insulin above 10 mIU/L; any diabetes medication alongside | Medication review if you take insulin or a sulfonylurea; otherwise meal timing and composition | HbA1c in all; insulin and HOMA-IR in Ultimate and Signature |
| hs-CRP and full blood count | Chronic infection and inflammation; the blood count is also the first screen for the blood disorders that cause night sweats | Raised hs-CRP; abnormal white cells, low haemoglobin or low platelets. Any of these with weight loss or fevers needs a GP promptly | GP with the results; a normal count and hs-CRP is genuinely reassuring | All panels |
| Morning cortisol and DHEA-S | A disrupted stress rhythm produces night sweats with early waking and a racing mind; very high or very low cortisol both need investigating | Morning cortisol at either extreme (drawn 8 to 9am) | Rhythm work for a mild pattern; a GP for an extreme result | All panels |
| Liver function (ALT, GGT) | Alcohol is one of the commonest causes of night sweats and the one people least expect; a raised GGT is the marker that shows it | GGT raised, particularly with a raised MCV on the blood count | Reducing intake resolves it; the retest shows the GGT falling | All panels |
Thresholds are UK laboratory conventions and NICE guidance where it exists. Your report reads each result against the others. Guides: perimenopause, thyroid, testosterone, insulin resistance, hs-CRP, cortisol, liver.
Read it in context
Women 40 to 55
FSH rising, oestradiol low, often with a ferritin dropping from heavier periods and a thyroid that needs ruling out because it mimics the same picture. NICE tells GPs not to use FSH over 45, which is right as a diagnostic rule and unhelpful when you want to understand what is happening. The panel gives you the hormone, thyroid and iron picture together. Menopause blood test.
Men
Night sweats in men get dismissed more often than in women, and the three commonest explanations are all measurable: low testosterone, an overactive thyroid, and alcohol showing as a raised GGT. Each has a straightforward answer once you know which it is.
Everything normal
A clean blood count, a normal hs-CRP and normal hormones and thyroid make the serious causes much less likely and point to the common ones a blood test cannot see: the bedroom, the duvet, alcohol in the evening, spicy food, anxiety, and medications such as SSRIs, which are a frequent and reversible cause.
Which panel
Advanced
74 biomarkers · £269
Full thyroid with antibodies, core sex hormones, full blood count, hs-CRP, HbA1c, morning cortisol and DHEA-S, liver including GGT, ferritin with iron studies. Everything except fasting insulin and the complete hormone panel.
View AdvancedAll seven causes
Ultimate
114 biomarkers · £349
Adds oestradiol, FSH, LH, progesterone, SHBG and free testosterone, plus fasting insulin and HOMA-IR for the overnight glucose dip. The panel for night sweats where perimenopause or testosterone is the question.
View UltimateSignature
230 biomarkers · £799
Processed by Randox. Adds an autoimmune profile and extended inflammatory markers, for night sweats alongside joint pain, rashes or other systemic symptoms.
View SignatureClinic draw £19. At-home £39. Morning slot, fasting from 10pm: hormones, cortisol and insulin all need it. If you still have cycles, day 2 to 5 gives the clearest hormone reading. Pay monthly available.
Honest comparison
A fair few night sweats have no blood marker at all. A too-warm room or a synthetic duvet is the most common cause of all and no test will show it. Alcohol in the evening causes sweats through a mechanism that only shows in the blood if drinking is heavy enough to lift the GGT. Several common medications do it, notably SSRIs and other antidepressants, some blood pressure drugs and tamoxifen, and the answer there is a prescriber conversation, not a panel. Anxiety and nightmares produce genuine drenching sweats. And sleep apnoea causes them too, which is worth knowing if you also snore. The value of the panel is that it settles the medical half of the list in one go, including the reassurance of a normal blood count and hs-CRP, so the remaining causes are the ones you can actually do something about. The blood markers behind poor sleep.
After your result
Hormonal, thyroid, metabolic, inflammatory, alcohol-related or none of them, with each marker read against the others and reviewed by a medical professional.
An overactive thyroid, a perimenopausal picture where you want HRT, a low testosterone, or an abnormal blood count all need a prescriber. The report tells you which results to show them and why. What to ask your GP for.
Starting HRT, treating a thyroid, cutting alcohol or fixing overnight glucose all show in the blood within twelve weeks, and the second report tells you whether the sweats stopped for the reason you think. Retest plans.
FAQs
Oestradiol and FSH in women, testosterone and SHBG in men, a full thyroid panel with antibodies, a full blood count, hs-CRP, HbA1c with fasting insulin, morning cortisol and liver function including GGT. Together they cover the measurable causes.
In women between 40 and 55 with changing periods, usually. But an overactive thyroid produces an almost identical picture and is easy to miss, and night sweats also occur in younger women and in men, where the causes are different. Testing separates them.
Yes. Low testosterone causes night sweats and hot flushes in men by the same mechanism that low oestrogen does in women. It is common after 50 and rarely offered as an explanation. Testosterone should be measured on a morning sample, and two readings are needed before any treatment.
See a GP promptly if they come with unexplained weight loss, fevers, a persistent lump or swollen gland, a cough that will not clear, or recent travel to an area with tuberculosis or malaria. Those combinations need examination rather than a private blood test. Night sweats on their own, with none of those, are far more likely to be hormonal, thyroid or lifestyle-related.
Not reliably on its own. A full blood count and hs-CRP can show changes that prompt further investigation and a normal result makes it less likely, but lymphoma is diagnosed by examination, imaging and biopsy. If you have night sweats with weight loss, fevers or a lump, see a GP rather than relying on any blood panel.
Very commonly, and it is the cause people least expect. Alcohol dilates blood vessels and disrupts the second half of the night. If drinking is regular and heavy, a raised GGT on the liver panel shows it, and the marker falls within weeks of cutting back.
A morning appointment, fasted from 10pm, because cortisol, testosterone and fasting insulin all depend on it. If you still have periods, days 2 to 5 of your cycle give the clearest FSH and oestradiol reading. Full preparation guide.
Seven causes in one morning venous draw, at 103 UK clinics or at home, with a report within 48 hours that says which one it is and who should see it next.
Perimenopause · Menopause · Poor sleep · Low libido · Find a clinic
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