Night sweats: causes, red flags and when to see a GP

It is normal to sweat at night if the room or bedding is too warm, and many people wake damp in summer. The NHS draws the line at drenching: night sweats are when you sweat so much that your night clothes and bedding are soaking wet even though the place you sleep is cool. They can affect adults and children.

The distinction matters because ordinary overheating needs only lighter bedding, while repeated drenching episodes, especially when they wake you, can reflect hormonal change, infection, medicines or a more serious illness.

The NHS lists the most common reasons for night sweats, and clinicians consider them first.

• Menopause and perimenopause: the NHS says hot flushes can happen during the day or night, make you sweat a lot, cause palpitations or anxiety and last for several minutes, and that sleep problems may be worse with night sweats. Changes to periods are usually one of the first signs.

• Anxiety, which can cause sweating and a racing heart at night.

• Medicines, such as some antidepressants, steroids and painkillers; the NHS says that if a GP thinks a medicine is causing night sweats they may prescribe a different one.

• Low blood sugar (hypoglycaemia), particularly in people on insulin or some diabetes tablets.

• Alcohol or drug use.

• Hyperhidrosis, a harmless condition that makes you sweat too much all the time.

• An overactive thyroid: the NHS lists sensitivity to heat, weight loss, a fast heartbeat, nervousness and tiredness among symptoms, so night sweats can be part of the picture.

Some infections cause fever and sweats, and tuberculosis is the best known in this context. The NHS TB page lists a cough lasting more than 3 weeks, tiredness, a high temperature or night sweats, loss of appetite and weight loss among TB symptoms, and says TB usually affects the lungs.

Blood cancers also feature. The NHS says symptoms of non-Hodgkin lymphoma include a painless lump or swelling, usually in the neck, armpit or groin, which is the most common symptom, plus a high temperature, night sweats, shortness of breath, itchy skin and sudden unexplained weight loss. It stresses that these symptoms are common and can be caused by many conditions, and that having them does not definitely mean lymphoma, but they should be checked by a GP because early treatment is more likely to be successful.

• See a GP if night sweats happen regularly, wake you up or worry you, as the NHS advises.

• See a GP promptly if night sweats come with a very high temperature or feeling hot, cold or shivery, a cough or diarrhoea.

• See a GP promptly if you are losing weight for no reason; the NHS lists this explicitly with night sweats.

• Seek an early appointment for a new painless lump in the neck, armpit or groin, persistent itching without rash, breathlessness or marked tiredness; the NHS lists these among non-Hodgkin lymphoma symptoms.

• Seek urgent advice if night sweats come with a persistent cough lasting weeks, coughing up blood or chest pain.

• Call 999 or go to A&E for fever with a rash that does not fade under a glass, severe headache and stiff neck, confusion or difficulty breathing.

Questions include how often the sweats happen, how drenching they are, whether you have a fever when you check, weight change, appetite, cough, itching, pain, lumps, periods and menopause symptoms, recent travel, contact with TB, medicines and alcohol, and whether you have diabetes. The NHS says the GP will want to check if you have any other symptoms.

The examination covers temperature, pulse, blood pressure, weight, glands in the neck, armpits and groin, the thyroid, heart and lungs, and the tummy for an enlarged liver or spleen. If lymphoma is suspected the NHS says the GP will ask about symptoms, may feel for lumps in the neck, armpit and groin and may arrange a blood test, with a referral to hospital for more tests if needed.

Common tests are a full blood count, inflammatory markers, thyroid function, blood glucose or HbA1c, liver and kidney function and, depending on the story, a chest X-ray, HIV and TB tests, or a scan. If swollen glands or other features raise concern, imaging and a biopsy through an urgent referral may follow.

The NHS says that if you have night sweats you will not usually need treatment, but the GP will check for other symptoms. Treating the cause is the aim: menopause treatment may be offered for menopausal sweats, medicines reviewed, thyroid disease treated, infection treated and so on. Practical measures include lighter bedding, a cool bedroom, breathable night clothes and avoiding alcohol and spicy food in the evening.