Sweating during sleep is surprisingly common, affecting about 41% of primary care patients in a large study. Most of the time, the cause is something simple: your bedroom is too warm, your bedding traps heat, or you had alcohol or a heavy meal before bed. But night sweats can also signal hormonal changes, medication side effects, infections, or sleep disorders, so it’s worth understanding the full picture.
How Your Body Temperature Shifts During Sleep
Your body doesn’t stay at one fixed temperature throughout the day. Your internal thermostat follows a 24-hour cycle, peaking in the late afternoon and dropping to its lowest point toward the end of your sleep phase. This natural cooldown is part of what helps you fall and stay asleep.
To shed heat, your body dilates blood vessels near the skin and activates sweat glands. That’s normal. You might notice slightly damp skin when you wake up, especially in warmer months, and it doesn’t mean anything is wrong. True night sweats are different: they soak your sheets or pajamas, wake you up, and happen repeatedly regardless of how cool your room is.
The Most Common Everyday Causes
Before looking at medical explanations, it helps to rule out the obvious. A bedroom that’s too warm, heavy synthetic bedding, or thick pajamas can all overwhelm your body’s cooling system. Drinking alcohol in the evening widens your blood vessels and increases heat loss through the skin, which triggers sweating. Spicy food does something similar by stimulating nerve receptors that raise your perceived body temperature. Intense exercise close to bedtime can keep your core temperature elevated longer than usual, making you sweat once you’re under the covers.
Natural-fiber bedding makes a real difference. Linen, for example, absorbs up to 20% of its weight in moisture without feeling damp, which helps wick sweat away instead of trapping it against your skin. Keeping your thermostat lower, using a fan, or switching to lighter sleepwear are all simple changes that resolve the problem for many people.
Hormonal Changes
Hormonal shifts are one of the most frequent medical causes of night sweats. During perimenopause and menopause, declining estrogen levels destabilize the part of your brain that regulates temperature. Your body misreads normal warmth as overheating and launches a full cooling response: flushing, rapid heartbeat, and drenching sweat. These episodes, often called hot flashes, are especially common at night and can persist for years.
Hormonal night sweats aren’t limited to menopause. Thyroid disorders that speed up your metabolism can raise your baseline body temperature and trigger overnight sweating. Low testosterone in men sometimes produces the same effect. Pregnancy, particularly the first and third trimesters, brings hormonal fluctuations that commonly cause night sweats as well.
Medications That Trigger Sweating
Several widely prescribed medications list night sweats as a side effect. The strongest evidence points to SSRIs (a common type of antidepressant), insulin and other blood sugar-lowering drugs, and certain blood pressure medications called angiotensin II receptor blockers. Corticosteroids and thyroid hormone supplements have also been linked to night sweats, though the evidence is less robust. Methadone, used to treat opioid use disorder, is another well-known trigger.
If your night sweats started or worsened around the time you began a new medication, that timing is a useful clue. Adjusting the dose or switching to a different drug in the same class often resolves the problem, but changing medications is something to work through with your prescriber rather than doing on your own.
Sleep Apnea and Night Sweats
Obstructive sleep apnea, a condition where your airway repeatedly collapses during sleep, is an underappreciated cause of night sweats. In one study, 34% of patients with severe sleep apnea experienced excessive overnight sweating. The mechanism involves your nervous system: each time your airway closes and oxygen drops, your body triggers a stress response that spikes heart rate and blood pressure. That heightened state of arousal activates your sweat glands. Even mild sleep apnea can cause this if your nervous system is particularly sensitive to the disruption.
If you sweat at night and also snore loudly, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea is worth investigating. Treating the apnea, typically with a device that keeps your airway open, often resolves the sweating too.
Infections and Illness
Night sweats are a classic symptom of certain infections. Tuberculosis is the most historically recognized, but colds, the flu, and COVID-19 all commonly cause overnight sweating as your immune system fights the infection. Bacterial infections like endocarditis (an infection of the heart lining) and osteomyelitis (a bone infection) can produce persistent, drenching night sweats as well. HIV is another infection where night sweats appear early and often.
Infection-related night sweats usually come with other symptoms: fever, chills, cough, fatigue, or unexplained weight loss. If the sweating is new, intense, and paired with any of these, it’s a signal that something beyond your sleep environment is going on.
When Night Sweats Point to Something Serious
Cancers of the blood, particularly lymphoma and leukemia, are known to cause drenching night sweats. These tend to be severe enough to soak through clothing and bedding, and they recur night after night. They’re often accompanied by unexplained weight loss, persistent fevers, and sometimes swollen lymph nodes you can feel in your neck, armpits, or groin.
Neurological conditions can also disrupt your body’s automatic temperature regulation. Damage to the nerves that control sweating, or conditions affecting the spinal cord, can cause sweating that seems disconnected from actual body temperature.
Night sweats deserve medical attention when they happen regularly, interrupt your sleep, come with fever or weight loss, or start well after menopause symptoms should have ended. A typical workup includes blood tests to check your blood cell counts, thyroid function, and inflammation markers, along with testing for tuberculosis and HIV, and sometimes a chest X-ray. In many cases, the evaluation is straightforward and identifies a treatable cause. And for the large number of people whose sweating comes down to a warm room, heavy bedding, or an evening glass of wine, the fix is even simpler.