Night sweats

Night sweats are episodes of heavy sweating during sleep. You may wake with soaked sleepwear or bedding, even though your bedroom is comfortably cool.

Sweating because the room is hot or your blankets are too heavy is not usually considered a medical night sweat. Occasional mild sweating is also common and may not have a clear cause.

Night sweats are a symptom, not a disease. Possible causes range from your sleeping environment and hormonal changes to medicine side effects and, less often, an infection or another health condition. Most people with persistent night sweats do not have a serious underlying illness.

You may notice damp skin, wet hair, or sweat concentrated around your chest, back, neck, or face. Some episodes affect your whole body.

A more marked episode may:

• Soak your sleepwear, sheets, or pillow
• Wake you feeling hot, chilled, or uncomfortable
• Require you to change clothes or bedding
• Happen alongside flushing, a racing heartbeat, or shakiness

The timing can offer clues. For example, a hot flash often starts with sudden warmth in the face, neck, or chest. Low blood sugar may cause sweating with trembling, hunger, weakness, or confusion.

A warm bedroom, heavy bedding, non-breathable sleepwear, or a heated mattress can cause sweating at night. Alcohol, spicy food, caffeine, or exercise close to bedtime may contribute in some people.

Hormonal changes during perimenopause and menopause are common causes. Perimenopause is the transition before periods stop. Hot flashes can happen during the day or at night and may include flushing, sweating, and a rapid heartbeat.

Some medicines can increase sweating. Examples include certain antidepressants like sertraline or fluoxetine, steroid medicines, hormone treatments, and some medicines used for pain or fever. Alcohol or drug use, as well as withdrawal from these substances, can also cause sweating.

Other possible causes include anxiety, panic symptoms, acid reflux, an overactive thyroid, obstructive sleep apnoea, and low blood sugar. Sleep apnoea causes repeated pauses in breathing during sleep, often with loud snoring and daytime tiredness.

Less common causes include infections such as tuberculosis or HIV. Infections of the heart valves or other parts of the body can also cause sweating and fever. Blood cancers such as lymphoma can cause drenching sweats, but usually produce other symptoms too, such as unexplained weight loss, fever, persistent itching, or enlarged lymph nodes.

Call emergency services if sweating occurs with:

• Severe trouble breathing
• Chest pain or pressure
• Confusion, fainting, or a seizure
• Difficulty waking or staying awake
• Coughing up more than a few streaks of blood

These symptoms need urgent assessment regardless of whether the sweating happens at night.

Seek same-day medical advice if you have a fever and feel very unwell, or if you have a weakened immune system because of illness or treatment. You should also seek prompt advice if you use insulin or another medicine that can lower blood sugar and sweating occurs with confusion, severe weakness, or loss of coordination. Follow your established low-blood-sugar plan while arranging help.

Book a routine appointment if night sweats repeatedly soak your clothes or bedding, disturb your sleep, or have no clear environmental explanation. Arrange a review sooner if they occur with unexplained weight loss, recurring fever, a lasting cough, persistent diarrhoea, unusual pain, or a new lump or swollen gland.

A healthcare professional will ask when the sweating began, how often it happens, and whether the room or bedding may be too warm. They may ask about periods or menopause symptoms, medicines and supplements, alcohol or drug use, recent travel, infection exposure, and changes in weight.

Mention symptoms such as fever, cough, snoring, daytime sleepiness, diarrhoea, pain, palpitations, or swollen glands. Bring a current medicine list. Do not stop a prescribed medicine before discussing it with the prescriber.

An examination may include checking your temperature, heart rate, thyroid area, chest, abdomen, and lymph nodes. Lymph nodes are small glands that can swell during infections and some other illnesses.

Tests are not always needed. Depending on your history and examination, testing might include blood counts, thyroid or blood sugar tests, inflammation markers, or tests for particular infections. A chest X-ray or sleep assessment may be appropriate when symptoms point to a lung condition or sleep apnoea.

Treatment is based on the cause. Environmental sweating may improve after changing the room temperature, bedding, or sleepwear. Medicine-related sweating may improve after a clinician safely adjusts or replaces the medicine.

Menopause-related night sweats can be treated with hormonal or nonhormonal options. The best choice depends on your symptoms, medical history, preferences, and the benefits and risks of each treatment.

Infections, thyroid conditions, sleep apnoea, and blood sugar problems each need their own treatment. Night sweats alone do not show which treatment is appropriate.

While monitoring your symptoms, you can:

• Keep the bedroom cool and use lighter, breathable layers
• Keep water nearby and replace fluids lost through heavy sweating
• Note whether alcohol, caffeine, spicy food, or late exercise triggers episodes
• Record episodes, temperature, medicines, and related symptoms
• Check your glucose during an episode if advised for your diabetes care

Avoid starting supplements marketed for sweating without checking whether they could interact with your medicines or health conditions.

Sweating caused by a hot room or heavy bedding should improve once the environment changes. Episodes linked to a temporary infection usually settle as the illness improves.

Menopause-related symptoms may come and go over time. Medicine-related sweating may continue while the medicine is used, although changing the medicine or timing can sometimes help under medical supervision.

When night sweats persist, follow-up may be needed even if initial tests are normal. Keep track of new symptoms and return for review if episodes become more frequent, more severe, or begin to occur with fever, weight loss, cough, pain, or swollen glands.

Are night sweats a sign of cancer?

Most night sweats are not caused by cancer. Some blood cancers can cause drenching sweats, but there are often other signs, such as unexplained weight loss, persistent fever, itching, tiredness, or enlarged lymph nodes. Repeated unexplained episodes should be assessed rather than assumed to have one cause.

Can stress or anxiety cause night sweats?

Yes. Stress, nightmares, panic symptoms, and anxiety can activate the body's “fight or flight” response, which may increase sweating. A clinician can still check for other causes if the episodes are frequent or drenching.

Is a night sweat the same as a hot flash?

A hot flash is a sudden wave of heat, often affecting the face, neck, and chest. It may cause flushing, sweating, chills, or a racing heartbeat. Hot flashes can happen while awake or asleep; nighttime episodes are often called night sweats.

Should I stop a medicine that may be causing sweating?

Do not stop a prescribed medicine suddenly. Some medicines can cause withdrawal symptoms or allow the condition being treated to worsen. Ask the prescriber or a pharmacist whether sweating is a known side effect and whether a safe adjustment is possible.