Night sweats – symptoms and causes

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What are night sweats?

Whilst many of us have woken up in the middle of the night feeling too warm to be comfortable, night sweats are something different. People with night sweats consistently wake up with damp or soaking sheets. It’s not because the weather is warm or they’re wrapped up in too many blankets. This is a condition that affects people all year round. 

Some people with night sweats will continue to sleep through the night, for others it will cause disrupted sleep. For everyone, it can cause discomfort and embarrassment, especially if they share a bed with a partner. But why do night sweats happen? And what can you do about them? We take a look.

What are the causes of night sweats?

Although the evidence isn’t 100% clear, biologically, night sweats seem to happen as a result of rapid changes in our blood vessels. Initially, the vessels expand, allowing more blood flow, which should help heat escape from the body. But with night sweats, the blood vessels then contract. This causes a hot flash throughout the body, which leads to excess sweating. 

They can also be affected by an individual’s thermoneutral zone. This is the range of temperatures that your body is naturally comfortable with, and the natural internal temperature you maintain. 

The thermoneutral zone helps each person’s regulatory system determine when they should sweat, and when they should shiver. Once you go outside of this core thermoneutral zone, your body has to start burning more energy to work to keep your internal temperature comfortable. The zone is determined by age, gender, body composition and energy expenditure, amongst other things. For some people who have night sweats, this can be associated with their thermoneutral zone changing during sleep. 

Night sweats can affect everyone. 41% of people reported having night sweats in the last month, according to the Sleep Foundation, which just shows how common they are. They tend to happen in people aged 41-55, and for those who have a pre-existing condition that leaves them more likely to overheat. We’ll take a closer look at some of these pre-existing conditions later.

Should I be concerned about night sweats?

It can be unpleasant to wake up in the morning with wet sheets, but you don’t always need to be worried about night sweats. The NHS recommends that if they’re waking you up in the night, or are accompanied by a high temperature, cough, diarrhoea, or unusual weight loss, then you should contact your doctor. 

They’ll then be able to check your symptoms and talk to you about some of the common reasons for night sweats. It’s not always possible to understand why someone is experiencing night sweats, but they can offer advice on handling the issue to help you get more comfortable. 

Difference between men and women

Women are more likely to experience night sweats than men. This is primarily because they’re a common side effect of perimenopause and menopause, as well as premature ovarian insufficiency, which causes a woman’s body to mimic menopause symptoms much earlier than usual.  The regular hormone fluctuations in women due to the menstrual cycle can also affect the regularity of night sweats. They’re also common in pregnancy.  

Some nights sweats in men are caused by low testosterone levels, specifically male hypogonadism. This is a condition where the body doesn’t produce enough testosterone or sperm. Men can either have this from birth or develop it later in life, most commonly as a result of injury or infection. Night sweats as a result of male hypogonadism can be treated with testosterone replacement therapy. 

Pre-existing health conditions and night sweats

Whilst you shouldn’t immediately jump to the assumption that your night sweats are a result of another condition, they are a common side effect for several medical issues. If you’re concerned, or have any other symptoms that are unusual for you, make sure to contact a doctor. 

At your appointment, your doctor will ask you questions about your symptoms and run tests that will help rule these conditions out, if necessary.  If you’re on medication, you may find that your doctor assesses whether switching to a different medicine could help ease your night sweats. 

Let's take a look at some of the most common medical reasons for night sweats.


Sweating is a normal bodily function that helps us control our temperature and cool down. However, hyperhidrosis is a medical condition that means that you sweat excessively, even when you’re not hot or exercising. 

According to Hyperhidrosis UK, there are two types of the condition, primary and secondary. Primary refers to someone who has experienced this excess sweating since childhood, and there is no known cause. However, they state that it’s unlikely that primary hyperhidrosis will cause night sweats.

Secondary hyperhidrosis is usually caused by another medical condition, or as a side effect of medication. Patients with secondary hyperhidrosis are likely to also have night sweats, rather than only experiencing excessive sweating during the day.


Sweating can both be a symptom of cancer, and a side effect of cancer treatment. However, there’s no need to initially panic and be concerned that your night sweats indicate that you have cancer – there are many other causes. Contacting your doctor about your night sweats will mean that they will do a range of tests, so you can be sure that any issues will show up at this stage.

If you are being treated for cancer, you may experience excess sweating, including at night. This is likely to be as a result of an infection, as your body sweats to try and fight this. There are also some cancers which cause excess sweating, and treatments such as chemotherapy cause hormone changes, which in turn cause you to sweat. 

Women who are receiving treatment for breast cancer may also go into early menopause, which causes hot flushes. Men who are being treated for breast cancer or prostate cancer may also have excess sweating due to low testosterone.

Mental health

People who are suffering from mental health problems including stress and anxiety may find they sweat more, as these conditions make our stress glands more responsive. This is because when we’re stressed, our body temperature rises, in preparation for the fight or flight response. Whilst it’s not been proven, one theory is that this is because stress emits an odour

In animals, this odour signals to other members of the pack that there is danger, so this could also be true for humans – a hangover from our hunter-gatherer days. There are two types of sweat, with stress sweat happening immediately, whereas exercise sweat is slightly delayed. This could also support this theory, as the danger signal would need to happen straight away in order to give a warning.

What can I do to ease night sweats?

If you’re struggling with night sweats, there are some things that you can do to try and make things better. Whilst you should still see your doctor if you’re concerned, making these adjustments can help whilst you’re waiting for an appointment, or if the doctor has confirmed that there’s no underlying condition that needs to be treated. 


Don’t worry, you don’t need to buy a specific luxury brand of pyjamas to help cool you down at night. Loose-fitting clothing made from linen, cotton and merino wool are the best choices if you want to stick to natural materials, which tend to be the most breathable options. However, whilst these fabrics will pull moisture away from your skin, they will soak up the sweat. They’ll keep you cool, but be warned that you’re likely to need to change your pyjamas more regularly. 

If you don’t mind splashing some cash and choosing something made specifically for cooling and keeping dry, then look for wicking fabrics. These pull moisture away from the skin, and it then evaporates rather than soaking your clothes. This may help people who find that they wake up in the middle of the night due to discomfort from damp clothes. 

Duvet and bedding

We all generally have a temperature we know that we can comfortably fall asleep in. Some people like to keep things cool, whilst others bundle up and then throw the duvet off in the middle of the night. However, for people with night sweats, it’s important to adjust your bedding accordingly, in order to give the best quality of sleep.

Whilst some companies now make good quality synthetic bedding, generally the best rule is to stick to natural fabrics like cotton and linen to help with breathability. When it comes to your duvet, choose a low tog rating. If you have the budget, choosing a down duvet can also help with air circulation, which in turn improves cooling. 

If you share your bed, you might have to get your partner on board with this, and potentially get them to layer up with blankets rather than put a heavier duvet on in the winter. Some companies now offer a ‘half-and-half duvet’, where you can have one tog rating on one half, and then a different tog rating on the other half. This might be a good option, depending on how much your partner wants to vary the weight of their duvet during the year.

Room temperature

The key part of medical-related night sweats is that they don’t happen purely because your room is too hot. However, making an effort to stop you overheating as a result of the room temperature won’t cause any harm. 

Your ideal room temperature will be a personal choice, but you’re unlikely to want to sleep with the window open all the time, lest you lose all the heat in the rest of your home. Instead, try using a quiet fan to direct air onto your side of the bed without disturbing you. This can also be a good compromise if you sleep with a partner too, as they probably won’t want to sleep in freezing temperatures just to keep you comfortable.


The hours before you actually get into bed are key when preparing for a good night’s sleep. Caffeine, alcohol and spicy foods can all cause your internal body temperature to spike, so avoid them if you suffer with night sweats. Ideally, the Sleep Foundation recommends that you try and stop drinking caffeinated drinks at least 4-6 hours before you want to sleep in order to get a good rest. Whilst doing this won’t cure your night sweats, it might help you stay asleep for longer.

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