Why Do I Wake Up Sweating, and When Should I Worry?

You surface at three in the morning with a damp pillow and the duvet thrown off. Most of the time the explanation is close at hand: a bedroom that is too warm, bedding that is too heavy or nightwear that traps heat. Hormonal changes, an evening drink, a passing infection, stress and some medicines are other common culprits. Only occasionally is sweating at night a sign of something that needs investigating, and those cases usually come with other clues. Here is how to work through the possibilities calmly.

Check the bedroom first

Before thinking about anything else, run through the simple things around you:

• Is the radiator or heating on overnight, or is the room warm and stuffy with the window closed?
• Are you sleeping under a winter-weight duvet all year round?
• Is the mattress protector, pillow or nightwear made of a synthetic fabric that holds heat?
• Does a partner, child or pet share the bed and add extra warmth?

Small changes here fix a surprising number of sweaty nights. Our answer on the best bedroom temperature for sleep covers cooling a room without air conditioning, and the piece on sleeping naked or in pyjamas looks at what to wear, or not wear, to bed.

Is it night sweats, or just being too warm?

There is a difference worth noticing. Feeling hot and a little clammy in a warm room is simply overheating. True night sweats tend to soak your nightwear or sheets, sometimes enough that you need to change them, and they happen even when the room is cool and the bedding is light. If you have already cooled the room and switched to a lighter duvet and the drenching continues, it is worth looking further.

Common everyday causes

Hormones and the menopause

Night sweats are one of the best-known signs of perimenopause and menopause, often arriving alongside hot flushes during the day and changes to periods. They can disturb sleep for months or longer. Cooling strategies help, and there are both lifestyle approaches and medical treatments a GP can talk through. Our answer on natural allies for menopausal well-being covers the wider picture.

Medicines and blood sugar

A number of commonly prescribed medicines list sweating as a possible side effect. If your night sweats started soon after a new prescription or a dose change, mention it to a pharmacist or GP, but keep taking the medicine until you have spoken to them. People who take medicines for diabetes should also know that low blood sugar at night can cause sweating, often with shakiness, confusion or vivid dreams. If that sounds familiar, follow your diabetes plan and contact your diabetes team or GP.

Small changes worth trying tonight

1. Turn the heating down or off in the bedroom and crack a window if it is safe to do so.
2. Swap to a lighter duvet, or use layers you can remove during the night.
3. Choose cotton or linen sheets and nightwear rather than synthetics.
4. Keep a glass of water by the bed.
5. Go easy on alcohol, large meals and very spicy food in the hours before bed.
6. Note what happens over a week or two: room temperature, drinks, stress and how damp you were on waking.

When should I see a GP?

Make an appointment if:

• You have drenching sweats that keep coming back over several weeks, even in a cool room.
• Sweats come with unexplained weight loss, a fever that keeps returning or swollen glands.
• You have a cough that will not go away, or you feel generally unwell and run down.
• The sweating started after a new medicine.
• Night sweats are disrupting your sleep and daily life, whatever the cause.

Get urgent medical help if sweating comes with chest pain, breathlessness, confusion or feeling very unwell.

What will the GP ask?

Expect questions about when the sweats started, how often they happen, how soaked you get, other symptoms, medicines, alcohol and, where relevant, periods. Bringing the short diary from the list above makes the appointment far more useful.

The short answer

Most sweaty nights come down to warmth, bedding, hormones, alcohol or a passing illness, and the first few respond well to simple changes. True night sweats that soak the sheets again and again, or that come with other symptoms, deserve a GP's attention rather than another fan by the bed.