Night Sweats: Why You Wake Up Sweating, the Causes, and When to See a Doctor

TL;DR

• Night sweats mean sweating that soaks clothing or bedding and that a warm room doesn't explain. Sleeping too hot is a different problem with a simpler fix.
• They are common and under-reported. In a survey of 2,267 primary care patients, 41 percent had sweated at night in the past month, and most had never told their doctor.
• The causes with the best support are menopause and perimenopause, medications including SSRIs, evening alcohol, hot flushes, panic attacks and sleep problems. Infection, thyroid disease and lymphoma are rarer and are the reason persistent sweats get investigated.
• A cool room, breathable bedding and no alcohol in the evening reduce the episodes while the cause is being worked out.
• Sweats every night for more than a few weeks, or sweats with weight loss, fever or swollen lymph nodes, need a GP appointment.

Waking up damp, or soaked enough to change the sheets, is more common than most people say out loud. The symptom has causes that run from harmless to serious, and the way to tell them apart is to think systematically rather than assume one explanation.

What counts as a night sweat

Waking warm because the room is hot, or because the duvet is too heavy, is not a night sweat in the clinical sense. Night sweats are episodes of heavy sweating during sleep that soak clothing or sheets and can't be put down to the sleeping environment. They often wake the person, and they tend to happen in the first half of the night when deep sleep is concentrated.

Your core body temperature isn't constant overnight. It falls in the evening as part of falling asleep, bottoms out in the early hours, then climbs toward morning. The hypothalamus runs that cycle as the body's thermostat. When something pushes heat production up, or makes the thermostat oversensitive, it responds by sweating to shed heat.

How common they are

A cross-sectional study across two primary care networks surveyed 2,267 adults. Forty-one percent reported night sweats in the previous month: 23 percent with sweating at night only and a further 18 percent with sweating both day and night. Prevalence peaked between the ages of 41 and 55 in both men and women. A majority had not reported the sweats to their physician, even when frequent and severe (Mold 2002).

The same survey looked at what travelled with the sweats. In women, pure night sweats were associated with hot flushes and panic attacks. In men, with sleep problems. Day-and-night sweats were associated with higher weight, hot flushes, sleep disturbance, antihistamines and antidepressants in women, and with higher weight, hot flushes and greater alcohol use in men.

The causes the research supports

A systematic review of the literature concluded that many suggested causes are poorly supported, that night sweats appear to be a nonspecific symptom, and that life expectancy in primary care patients who report them did not appear to be reduced (Mold 2012). That is reassuring context. These are the causes with the best footing.

Menopause and perimenopause

The most common cause in women in their forties and fifties. Falling oestrogen narrows the range of core temperatures the hypothalamus tolerates, so small changes trigger a full heat-loss response: flushing, sweating and a racing heart (Freedman 2014). The same mechanism is behind the sweating many women notice in the weeks after giving birth, when hormone levels drop sharply.

Medications

Antidepressants are among the most common culprits, SSRIs and SNRIs in particular, and the primary care survey found SSRI use associated with sweating (Mold 2002). Antihypertensives, antipyretics, steroids and some diabetes medicines are also listed (Viera 2003). If the sweating started soon after a new prescription, that is the first thing to raise with the prescriber. The review found that alpha-adrenergic blockers may reduce night sweats in patients taking serotonin reuptake inhibitors, which is a conversation for the doctor rather than a reason to stop a medication (Mold 2012).

Alcohol

Alcohol taken in the evening is sedating first and disruptive later. As it is metabolised in the second half of the night, sleep becomes lighter and more fragmented (Roehrs 2001), and sweating is a common part of that rebound. The primary care survey found greater alcohol use associated with sweating in men. The detail is in night sweats and alcohol.

Stress, anxiety and panic

Cortisol and adrenaline raise body temperature and can surge overnight, particularly in the early hours when cortisol naturally rises. Panic attacks were one of the two factors associated with pure night sweats in women in the primary care survey (Mold 2002). For the stress side, see cortisol and sleep.

Sleep apnea

Each breathing pause drops oxygen and ends with an arousal and a burst of adrenaline, which raises heart rate and sweat production. Obstructive sleep apnea is on the list of diagnoses to consider in night sweats (Viera 2003), and many people with it don't know they have it. Loud snoring, witnessed pauses and daytime sleepiness alongside the sweating point this way. See sleep apnea symptoms.

Blood sugar dips and thyroid

When blood glucose falls overnight, the body releases adrenaline to correct it, and that surge generates heat and sweating. Hypoglycaemia and hyperthyroidism both appear in the diagnostic list (Viera 2003). An overactive thyroid raises baseline metabolism and temperature and is one of the medical causes a blood test can confirm or rule out.

Infection and lymphoma

Tuberculosis and lymphoma are the diseases in which night sweats are a dominant symptom. They are infrequently found to be the cause in modern practice, and they remain the reason a doctor takes persistent, unexplained sweats seriously (Viera 2003). HIV and other chronic infections are also on the list.

Simply sweating more

Some people sweat more than average, day and night, with no medical cause. It tends to run in families. It is benign and annoying.

When to see a doctor

Night sweats with a clear explanation, such as menopause, a new medication or evening alcohol, that ease when the cause is addressed don't need urgent investigation.

These combinations do: drenching sweats every night for more than a few weeks with no obvious cause; sweats with unexplained weight loss; sweats with a persistent fever; sweats with swollen lymph nodes in the neck, armpits or groin; sweats in someone with a history of cancer; or sweats alongside any other new and unexplained symptom.

A GP will take a history, review medications and, if nothing obvious turns up, consider a blood count, thyroid function and inflammatory markers as a starting point, with further tests only if those point somewhere (Viera 2003).

What helps while you find the cause

Start with the room. The range often cited as comfortable for sleep is around 16 to 19 degrees Celsius, and warmer rooms will cause sweating in most people. Natural fibre bedding, cotton or linen, manages moisture better than synthetics. Lightweight sleepwear and a fan aimed at the body help. See best sleep temperature.

Then the evening. Alcohol within three hours of bed is the most common reversible trigger. Spicy food raises heat during digestion. Late caffeine keeps the arousal system active. A trial period without them often shows within days whether they were the driver.

Where a specific cause is identified, treating it is the main approach. For menopausal sweats, hormone therapy is the most effective treatment when appropriate, and non-hormonal options exist for women who can't take it. That is a conversation with a doctor.

Waking repeatedly from sweats leaves you with the same tired mornings as any other fragmented night. See why you wake up tired.

Frequently asked questions

Why do I wake up sweating when it's not hot?

Night sweats that a cool room doesn't explain usually trace to hormones, a medication, evening alcohol, a stress-hormone surge, a blood sugar dip or a breathing problem. In a primary care survey the strongest associations were hot flushes, panic attacks, sleep problems, antidepressants and alcohol (Mold 2002).

Are night sweats a sign of something serious?

Usually not. A systematic review found the symptom nonspecific and life expectancy in primary care patients who report it not reduced (Mold 2012). The combinations that need a doctor are sweats with weight loss, fever or swollen lymph nodes, or sweats every night for weeks with no clear cause.

Can anxiety cause night sweats?

Yes. Panic attacks were associated with night sweats in women in the primary care survey, and stress hormones raise body temperature overnight. Sweating from this cause tends to ease as the anxiety is managed.

Are night sweats always menopause?

No. Menopause is the most common cause in women in their forties and fifties, and night sweats occur in men and in women of all ages. Medications are one of the most common causes across every group.

What can I do tonight?

Cool the room to around 16 to 19 degrees, switch to cotton or linen bedding and light sleepwear, and skip alcohol within three hours of bed. Those three changes remove the most common triggers while you work out the rest.

Disclaimer

This article is for general information only. It is not medical advice and it does not replace guidance from a qualified healthcare professional. Night sweats have many causes, most of them benign. If yours are persistent, drenching, or come with weight loss, fever or swollen lymph nodes, speak with your GP. Do not stop or change a prescribed medication without talking to the prescriber.