Night Sweats: Causes and When to Worry

Night sweats are repeated episodes of heavy sweating during sleep that soak your nightclothes or bedding. They’re common and usually harmless, but occasionally they’re a sign of an infection or other illness that needs attention.

Imagine waking three nights a week with soaked sheets. You change the duvet, turn down the heating and stop late-night spicy food, but it keeps happening. You’ve also lost weight without trying. Telling your doctor about both symptoms together leads to the right tests and a treatable diagnosis.

Common causes

• Hot bedroom, heavy bedding or warm nightclothes
• Menopause and perimenopause
• Medicines such as antidepressants, steroids, diabetes medicines and some hormone treatments
• Alcohol, caffeine and spicy food in the evening
• Anxiety
• Infections including flu and, importantly, tuberculosis and HIV
• Low blood sugar overnight in people taking diabetes medicines
• Overactive thyroid
• Sleep apnoea
• Less commonly, cancers such as lymphoma

What helps

• Keep the bedroom cool and use layers you can remove
• Choose breathable cotton or moisture-wicking nightwear
• Keep cold water by the bed
• Cut back on alcohol, caffeine and spicy food in the evening

But when should I worry?

See a doctor if night sweats happen regularly without an obvious cause, or come with fever, unexplained weight loss, a persistent cough, swollen glands, extreme tiredness or diarrhoea. These combinations need investigation, including tests for infection. If you’re going through menopause and sweats disrupt your life, treatments including HRT can help.

Sources: NHS (Night sweats), Mayo Clinic, Cleveland Clinic, World Health Organization (Tuberculosis).