You slip into peaceful slumber, snuggled up in a bed that’s just the right temperature, only to wake up hours later drenched in sweat. Your pyjamas stick to your skin, the sheets are soaked, and suddenly, you’re wide awake. Confusion and worry set in: what’s going on?
Sweating is normal. It’s our natural way of cooling down, kicking in when the body gets too warm. When you exercise, drink one too many drinks or spend the night under a heavy duvet, your hypothalamus (the part of your brain responsible for temperature regulation) signals to certain glands to release that clear, odourless fluid.
As the sweat evaporates, your body cools down and is able to maintain the necessary temperature to function properly.
But tonight feels different. Nerve cells (so-called thermoreceptors) in your organs, blood vessels and spinal cord have sent the signal to your hypothalamus that it needs to cool you down – yet your duvet isn’t heavy and the room isn’t hot. Nevertheless, once again, you’ve woken up drenched in sweat.
But you’re not alone. Night sweats are surprisingly common if you consider the many causes that can trigger them. And, while they are notorious in women undergoing menopause, they can affect anyone, regardless of age or gender.
Over the years, researchers around the world have surveyed people and observed them in sleep laboratories to determine the symptoms associated with their night sweats, and the possible reasons for them. However, the number of people affected is likely still underestimated.
“Many individuals feel embarrassed or ashamed to discuss their experiences, fearing negative social judgement,” says Dr Linda Grosser, a sleep researcher at the University of South Australia.
Many people also simply don’t think it’s worth a trip to the doctor as it doesn't seem like a condition that urgently needs fixing. While temporary triggers like spicy foods or alcohol are not too bothersome, recurring night sweats can be more complex – and could be your body’s way of signalling something more serious.
“If someone experiences excessive sweating out of nowhere and it persists for at least two weeks, it’s worth seeing a doctor,” says Prof Adam Friedman of the George Washington University School of Medicine and Health, in the US.
So, what could be causing this nightly deluge?
Persistent sweating might point to underlying health issues ranging from hormonal changes to infections to cancer, and even hereditary conditions like primary hyperhidrosis, which affects nearly three per cent of the US and UK populations. This condition causes excessive sweating in areas like the palms of your hands, armpits, soles of your feet, or your face.
To get to the bottom of what might be giving you night sweats, dermatologists like Friedman typically start by asking you about your medical and family history. If the sweating is not a condition itself but a symptom, it’s called secondary hyperhidrosis.
This usually affects the whole body and can appear to occur for no apparent reason, Friedman explains. But on closer examination, based on blood analysis and your symptoms, an underlying health issue may emerge. “It’s important to figure out the main cause so we can manage it properly,” says Friedman.
The good news? We've found out (almost) every cause it could be – and what you can do about them.
1. It might be a sleep-related breathing disorder
The link between persistent night sweats and their underlying health issues isn’t always clear at first glance, and obstructive sleep apnea (OSA) is a prime example. It is, first and foremost, a breathing disorder that occurs when the muscles supporting soft tissues in your throat, such as the tongue and soft palate, temporarily relax during sleep.
People with OSA can still breathe, but a narrowed upper airway makes it difficult to take in enough air.
As a result, breathing becomes very shallow and may stop for a brief moment. Unsurprisingly, these interruptions disturb sleep quality, often leading to daytime fatigue – even if you aren’t aware of what’s happening during the night.
Loud snoring is a telltale symptom of OSA, but interestingly, so is sweating. A 2013 study in Iceland found that people with this condition are three times more likely to sweat at night than the general population.
But why would a breathing disorder lead to night sweats? Each time breathing stops, even for just a few seconds, the body releases adrenaline and other stress hormones in an effort to get it going again. These hormones can alter body temperature, resulting in sweating, while also raising your heart rate and blood pressure.
The gold standard for diagnosing OSA is a sleep study called polysomnography, which is done overnight in a sleep laboratory. During this comprehensive test, doctors monitor your breathing patterns, brain waves, blood oxygen levels and heart rate, as well as eye and leg movements.
But you don’t have to go to a lab to find out – there are also simplified home tests: portable monitors with sensors on your wrists, fingers, and neck that can measure your breathing patterns, oxygen levels and heart rate.
Though the exact cause of sleep apnea remains unclear, there is an effective treatment: continuous positive airway pressure (CPAP), where you essentially wear a mask that delivers a steady flow of air to keep your airway open during sleep.
In the Icelandic study, the researchers followed up with their participants after two years and enquired about their symptoms: for the participants who used a CPAP machine almost daily, the frequency of night sweats dropped from 33 per cent to 12 per cent, while those who used it occasionally or not at all reported only slight improvements.
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2. It could be a different health issue
It makes sense that night sweats and sleep disorders go hand in hand. Research has shown that neurological disorders such as insomnia, restless legs syndrome (an uncomfortable urge to move your legs), and narcolepsy (where your brain’s ability to regulate sleep-wake cycles is impaired) can all play a role.
Why? They trigger the body’s natural fight-or-flight response to stress.
Then, when your brain recognises you’re in a stressful situation, it activates the sympathetic nervous system (the network of nerves running from the brain stem down the spinal cord and out into the body). As part of the fight-or-flight response, your heart rate and blood flow to the organs increase and – you guessed it – you start to sweat.
It doesn’t stop at sleep disorders, either. When it comes to night sweats, Friedman says there is a laundry list of potential underlying diseases and conditions. Some of these are serious, like tuberculosis (TB), which is the most common infection associated with night sweats.
During an infection, the immune system responds by releasing chemicals to fight off the TB bacteria, which raises the body’s temperature. When your immune system is running at full speed, which is usually at night during sleep, these symptoms worsen.
Night sweats can, although rarely, also be a symptom of certain cancers. However, doctors caution against jumping to conclusions on your own: “I want to make sure that people don’t go down the rabbit hole of Dr Google and think: ‘Oh, I sweat more at night, I must have cancer,’” says Friedman.
Nevertheless, he advises a visit to the doctor if night sweats persist for longer than two weeks to determine if there is an underlying health issue that can be treated. “In many cases, sweating won’t be the only sign or symptom,” he adds.
Ironically, some common medications, such as those used to treat antidepressants or diabetes, can actually trigger night sweats as a side effect. That’s because they interfere with your body's natural systems – for instance, antidepressants may raise your body temperature, while too much insulin from diabetes medication may cause your blood sugar level to drop too much.
This is called hypoglycaemia, and your body responds to it by releasing stress hormones and triggering sweating. If you suspect that low blood sugar could be causing your night sweats, an at-home glucose monitor can help track your blood sugar levels.
Pain relievers are also a usual suspect, according to the International Hyperhidrosis Society. That doesn’t mean you should stop taking your medications if you suspect they’re responsible for night sweats, says Friedman, but it’s certainly cause to talk to your doctor about the risks and benefits of stopping or switching them.
3. A common culprit: Hormones
Low hormone levels can disrupt your body's temperature regulation, leading to night sweats in both women and men. Oestrogen and testosterone both play a role in balancing the levels of the key neurotransmitters norepinephrine and serotonin in the hypothalamus, our internal thermostat.
When these hormones dip, the hypothalamus can misinterpret signals and trigger sweating as if the body were overheating – even during sleep.
For women, hormonal changes aren’t just a concern for those around the age of 50 – oestrogen levels can start dropping up to 10 years before the ovaries run out of eggs. As many as 10 per cent of women have menopause before they turn 45, which means symptoms like night sweats could begin as early as their mid-30s.
Some breast cancer treatments can also hasten menopause, leading to a significant drop in oestrogen production, which triggers those frustrating night sweats.
The link between low hormones and night sweats is well understood in women undergoing menopause. Hot flushes and night sweats are a notorious symptom, especially on the face, neck and chest, but night sweats are particularly problematic because of how they disrupt your sleep.
Myra Hunter, Emeritus Professor of clinical health psychology at King’s College London, notes that many people experience stress and anxiety around this symptom. “It's hard to know if night sweats wake you up or if you wake up feeling worried and irritated and then have a night sweat,” she says, adding that it's likely a mix of both.
Hormone replacement therapy (HRT) is the standard treatment for managing menopausal symptoms, including night sweats, but it can come with side effects. Another option is cognitive behavioural therapy (CBT), which focuses on changing your ways of thinking and behaviour.
This includes a calming evening routine to unwind from the day's stress, going to bed and getting up at consistent times, and creating a comfortable and relaxing sleep environment.
In November 2024, the UK's National Institute for Health and Care Excellence introduced CBT into its menopause guidance, recommending that talking therapy be offered alongside HRT or even as an alternative.
Clinical trials led by Hunter and other research groups have shown that CBT can reduce both the frequency of night sweats and the anxiety associated with them. The goal of CBT is to break the cycle of negative thoughts, Hunter explains, such as worrying about not being able to fall asleep after waking up drenched in sweat.
“We don’t expect to get rid of night sweats altogether, but we're helping to make them less bothersome and less disruptive to women's lives, so they don't dread going to bed,” she says. Simple relaxation and breathing exercise to help restore calm can make these disturbances less stressful.
It’s also not just for women – CBT is also encouraging news to other people who sweat excessively due to other hormonal changes.
For men, the issue is low testosterone. This can be a result of hormone therapy to treat prostate cancer or a condition called hypogonadism, when the body does not produce enough of the hormone.
About 35 per cent of men older than 45 and 30-50 per cent of men with obesity or type 2 diabetes have this condition. In these cases too, a hormonal imbalance throws off the body's internal thermostat and you may find yourself sweating, day and night.
4. Switch up your evening routine
Even if you can't completely avoid sweating at night, you can minimise it somewhat with your daily habits, even hours before going to bed. Everyone sweats after a workout, but the timing and intensity of your exercise can change your sleeping temperature.
High-intensity workouts raise your core temperature and speed up your metabolism, so working out later in the evening could make you more prone to night sweats. Your brain responds to the overheating by sweating to cool your body down, even hours after training.
After a workout or on a hot evening, it’s tempting to take a cold shower before bed. But this can actually work against you, according to Dr Christine Blume, sleep scientist at the University of Basel in Switzerland.
“Cold water can constrict blood vessels, which keeps the heat in the body instead of allowing it to escape,” she says, recommending a lukewarm shower instead.
Our bodies typically cool down a degree or two during the night. Perhaps surprisingly, taking a warm shower or bath one to two hours before bed can help trigger that process. While this may sound counterintuitive, raising your body temperature with warm water allows it to cool down more efficiently afterward.
Your bedroom temperature also plays a role here: for adults, between 16 and 19°C (61–66°F) is ideal. A cooler environment helps the body naturally lower its temperature, which is essential for falling asleep.
5. Your sleep setup might be wrong
You've reached the point where you've woken up drenched in sweat, and what should have been a peaceful night is now a restless one. Blume says that while sweat alone may not wake you up, “you will likely want to get up to change your wet pyjamas and even your bedding once you notice.” And that disruption can really take a toll on your sleep.
Sleeping nude doesn’t help much either in that case, as it can leave your skin feeling damp. Blume points out the advantages of breathable fabrics for sleepwear. “Choose materials that don’t trap moisture and dry quickly, so your sleep is less disturbed,” she says.
You may think wool doesn’t have a place in a cool sleeping environment, but studies have actually shown that fabrics such as Merino wool wick away heat and sweat more efficiently. Satin PJs may feel nice on the skin, but because they’re usually made from synthetic fibres, they can trap heat and moisture.
Linen is another good option for sleepwear and bedding, though it’s less suitable in the colder months given it doesn’t insulate as well as wool and cotton because of its hollow fibres.
Blume also recommends lightweight duvets that allow for easy adjustments during the night, like popping out a foot or hand to release heat. Our bodies release heat quickly from these extremities due to their large surface areas, dense networks of blood vessels and thinner skin.
Mattresses and toppers matter too: your memory foam mattress may be comfy, but this and other synthetic materials like polyester trap heat and moisture.
In a lab experiment at the University of Turin in Italy, people sleeping on so-called ‘high-heat capacity’ mattresses (which, in this study, had a foam core with a polyurethane coating) had lower back temperatures and rated their sleep experience more positively the following morning (compared to people who slept on 100-per-cent foam mattresses).
There are also mattresses that contain temperature-regulating gel beads to enhance cooling. Finding the ideal sleep setup can feel overwhelming with so many options available.
However, Blume encourages a bit of trial and error: “You can’t really go wrong,” she says. “What we find comfortable at night is very individual, just like our tendency to sweat. If one material feels scratchy or uncomfortable, simply switch to another.”
Love-it-or-your-money-back trials will help those on tighter budgets find what’s comfortable without breaking the bank. But, with each small change, you’re getting closer to a restful, sweat-free night – no matter your budget.
About our experts
Dr Linda Grosser is a sleep researcher at the University of South Australia. Her work has been published in Sleep, Sleep Advances and IFAC-PapersOnLine.
Prof Adam Friedman is a Professor of Dermatology at the George Washington University School of Medicine and Health, in the US. He has been published in Journal of the American Academy of Dermatology, American Journal of Clinical Dermatology and Dermatology and Therapy.
Myra Hunter is an Emeritus Professor of clinical health psychology at King’s College London. She has been published in Lancet Oncology, Menopause: Journal of the North American Menopause Society and Maturitas.
Dr Christine Blume is a sleep scientist at the University of Basel in Switzerland. Her work has been published in Nature Human Behaviour, Current Biology and SLEEP.
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