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Night Sweats: What Causes Them and When to Worry

Night sweats, drenching sweats that soak clothing and bedding despite normal room temperature, can be a sign of serious underlying disease or a benign menopause symptom.

Written by Suman Konda, PharmD, Clinical Pharmacist · Editorial policy · Not medical advice

Last updated: · How we check our content

Most common cause (women)
Menopause/perimenopause
Serious causes
Lymphoma, TB, HIV, leukaemia
Classic lymphoma triad
Night sweats + weight loss + fever
Infection causes
TB, HIV, bacterial endocarditis
Seek Urgent AssessmentNight sweats + unexplained weight loss + persistent fever (B symptoms) in a young person. This is the lymphoma red-flag triad. Requires urgent bloods (FBC, LDH, ESR) and imaging.

Causes by Clinical Context

CauseCluesTest
Menopause / perimenopauseWomen 45–55; flushing; mood changesFSH; clinical diagnosis
Infection (TB, endocarditis, HIV)Chronic fever, weight loss, risk factorsFBC, CRP, CXR, blood cultures, HIV test
Lymphoma (Hodgkin's)'B symptoms': night sweats + fever + >10% weight loss; lymphadenopathyFBC, LDH, ESR; CT scan; PET
MedicationsSSRIs, tamoxifen, GnRH analogues, opiatesDrug history
HyperthyroidismHeat intolerance, palpitations, weight lossTSH + Free T4
Hypoglycaemia (nocturnal)Diabetes on insulin or sulphonylureaNocturnal glucose check
Anxiety / PTSDNightmares, hyperarousalPsychological history
Simple Questions FirstAsk: are you waking drenched (soaking through sheets)? Is the room temperature normal? Are there other symptoms (weight loss, swollen glands, fever)? Simple benign night sweats don't drench clothing, rule of thumb.
What are B symptoms in lymphoma?
B symptoms are: fever >38°C, drenching night sweats, and loss of more than 10% of body weight in 6 months. Their presence upgrades lymphoma staging and is associated with a more aggressive disease course requiring more intensive treatment.
Does menopause always cause night sweats?
Menopause-related vasomotor symptoms affect 70–80% of women but with huge variation in severity. Night sweats are caused by oestrogen withdrawal affecting the hypothalamic thermostat. HRT is the most effective treatment.
Can antibiotics cause night sweats?
Yes. Rifampicin (used in TB treatment) commonly causes night sweats. Many antibiotics cause flushing or sweating as a side effect. A thorough drug history is essential.
Is hypoglycaemia at night dangerous?
Yes. Nocturnal hypoglycaemia in insulin-treated diabetes can be severe and is a common cause of 'dead in bed' syndrome. Modern continuous glucose monitors (CGM) with alarms have significantly reduced this risk.
MenopauseMost common cause

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Medical Disclaimer: This page is for general education only and does not replace professional medical advice. Always consult a qualified healthcare provider.