Sweating is a natural response by your body to prevent you from overheating. Sweat glands release sweat, a mix of water and other substances, through your skin. Heat is released as water evaporates from your skin, which cools your body down. Sweating is controlled by a part of your brain called the hypothalamus, which regulates your body temperature. The hypothalamus sends signals to over two million sweat glands to maintain the optimal body temperature.

Night sweating is different from the body's normal response to overheating eg when it’s too hot in your bedroom or you're using a heavy blanket. Night sweats are episodes of excessive sweating (hyperhidrosis) while you sleep that leave you, your nightwear and your bedding soaking wet.

Night sweats can affect people of all ages — adults and children.

They often go away without the need for treatment but if you’re worried, see your GP.

Causes of night sweats

In some cases, there is no particular reason for night sweats. In some cases, it is caused by hyperhidrosis, a condition that causes excessive sweating in the day and night — if it has no known cause it’s called idiopathic hyperhidrosis and if it has a known cause it is called secondary hyperhidrosis.

Other common causes of excessive sweating at night are:

Anxiety and stress — this can cause excessive sweating in the day and night
Gastroesophageal reflux disease (GERD) — persistent acid reflux due to problems with the muscle that closes your oesophagus
Low blood sugar (hypoglycaemia) — you’re at a higher risk of developing low blood sugar if you have diabetes
Low testosterone
Menopause — night sweats due to menopause usually occur alongside other menopausal symptoms such as hot flushes in the day, mood changes and vaginal dryness
Sleep apnoea — temporarily stopping breathing when sleeping; this is more common in men, occurring in one in four men

Other causes of night sweats include:

Side effects of certain medications — this includes:

Antipsychotics
Diabetes medication
Certain painkillers
Hormone therapy drugs
Selective serotonin reuptake inhibitors (SSRIs)
Steroids

Drug or alcohol abuse or withdrawal

Occasionally, night sweats can be a symptom of a serious underlying health condition, such as malaria, Hodgkin’s disease and cancer.

Getting a diagnosis for night sweats

If night sweats are regularly disturbing your sleep and, as a result, you’re suffering from fatigue, see your GP.

You should also make an appointment with your GP if, along with night sweats, you also have:

A cough
A very high temperature and/or feel feverish
Regular bouts of diarrhoea
Unintentional weight loss

Your GP will ask about your general health and any family history of excessive sweating or night sweats. They may arrange tests to check for any underlying reasons for your sweating and, if needed, will arrange appropriate treatment.

Treatments for night sweats

In many cases, medical treatment isn’t needed for night sweats. If treatment is needed it will depend on what’s causing your night sweats eg you may need to correct a hormone imbalance or have your existing medications adjusted.

How to stop night sweats

To manage excessive sweating at night, there are things you can try, including:

Avoiding possible triggers such as alcohol, spicy foods and caffeine, especially two to three hours before bedtime
Exercising regularly but not too close to bedtime
Keeping your bedroom cool eg using a fan or air conditioning
Losing any excess weight and eating a healthy diet, which is low in fat and sugar
Practising relaxation techniques — this can help reduce anxiety or stress and can be done throughout the day but also before bedtime and after waking from a night sweat
Wearing loose-fitting nightclothes and using bedding made from natural materials

To prevent dehydration, you can also drink lots of water.

Your GP or consultant can suggest other ways to control excessive sweating at night, such as using clinical-strength antiperspirants before bedtime on your back, chest, feet, groin, hairline, hands and underarms.

They may also recommend treatments for any underlying medical conditions.

If your night sweats are menopausal, they may discuss treatment to relieve your menopause symptoms, such as hormone replacement therapy (HRT).

If your night sweats are a side effect of medication, your doctor may change your medication or alter the dosage.

If anxiety is causing your night sweats, you may be referred for anxiety treatment, such as cognitive behavioural therapy (CBT).

Conditions related to night sweats

Hot flushes are sudden feelings of warmth, which can happen during the day or night. If they happen at night and cause you to sweat excessively, they are called night sweats.

Night sweats are therefore sometimes called hot flushes. However, hot flushes are not the same as flushing. Flushing is reddening of the skin caused by increased blood flow — this can occur alongside night sweats but do not itself cause excessive sweating.

Frequently asked questions

What are night sweats a sign of?

Night sweats may not be a sign of any underlying medical condition and may go away on their own. However, they can be a sign of gastroesophageal reflux disease (GERD), low blood sugar, low testosterone, menopause or sleep apnoea. In some cases, they may be a side effect of medication you are taking or caused by alcohol or drug abuse or withdrawal. Less commonly night sweats may be a sign of more serious conditions, such as cancer, Hodgkin’s disease or malaria.

When should I be concerned about night sweats?

If night sweats are occurring alongside a cough, fever, regular bouts of diarrhoea or unintentional weight loss, you should see your GP as soon as possible. You should also see your GP if your night sweats are regularly disturbing your sleep and leaving you fatigued.

Why do I wake up drenched in sweat at night?

There are many possible reasons for waking up drenched in sweat at night. You could be suffering from anxiety and stress, or you could have a medical condition, such as gastroesophageal reflux disease (GERD) or sleep apnoea. If you are a woman in your 40s or 50s, you may be going through the menopause. Night sweats can also be caused by low blood sugar and low testosterone.

What is the difference between night sweats and sweating at night?

Most people sweat to some extent at night. Sweating is your body’s natural response to maintain an optimal body temperature. Night sweats however refer to excessive sweating that soaks through your clothes and bedclothes and is not caused by the environment ie your bedroom being hot or using a heavy blanket.

What is the most common cause of night sweats?

Common causes of night sweats include going through the menopause, anxiety and stress, certain medications (eg certain anti-depressants, diabetes medications, steroids and painkillers), low blood sugar, and alcohol or drug abuse.

What are lymphoma night sweats like?

Lymphoma night sweats soak through your clothes and bedclothes and are often described as drenching.

What can I take for night sweats?

Treatment for your night sweats will depend on the cause. If they are due to an underlying medical condition, your doctor may recommend treatments specific to that condition. Night sweats can also be treated by using clinical-strength antiperspirants.

Are night sweats a symptom of diabetes?

Yes, night sweats can be a sign of diabetes as people with diabetes can have low blood sugar levels at night, which causes excessive sweating. However, certain diabetes medications can also cause night sweats.

Do thyroid problems cause night sweats?

Thyroid problems can cause night sweats. Night sweats are not usually caused by an underactive thyroid (hypothyroidism) but by an overactive thyroid (hyperthyroidism).