Night sweats happen when your body’s cooling system activates during sleep, soaking your clothes or sheets even when your bedroom isn’t hot. The causes range from a warm room or heavy blankets to hormonal shifts, medications, sleep disorders, and occasionally something more serious. Most people who search this question are dealing with repeated episodes and want to know what’s normal, what’s fixable, and what deserves a closer look.
Your Bedroom May Be the Problem
The simplest and most common explanation is an environment that’s too warm. Your core body temperature naturally drops during sleep, and your body sweats to make that happen. If your room is fighting that process, you’ll wake up damp. Sleep specialists at the Cleveland Clinic recommend keeping your bedroom between 60 and 67°F (15 to 19°C). Memory foam mattresses, synthetic sheets, and heavy comforters trap heat against your skin and can push you past the sweating threshold even in a cool room.
Before investigating medical causes, it’s worth ruling out the obvious: lower your thermostat, switch to breathable cotton or linen bedding, and sleep in light clothing (or none). If the sweating stops, you have your answer.
Hormonal Changes and Menopause
For women in perimenopause or menopause, night sweats are one of the most recognizable symptoms. Declining estrogen levels interfere with how the brain regulates temperature. Normally, your hypothalamus (the brain’s internal thermostat) tolerates small fluctuations in body temperature without reacting. That comfortable range is about 0.4°C wide. When estrogen drops, that range narrows dramatically. A tiny uptick in body temperature that would normally go unnoticed suddenly crosses a threshold, and your brain responds as if you’re overheating: blood vessels dilate, your heart rate increases, and sweat glands activate. The result is a hot flash or, when it happens during sleep, a night sweat.
These episodes can start years before your period actually stops and may continue for several years after. They’re not dangerous, but they can seriously disrupt sleep. Hormone therapy is one of the most effective treatments, though not every woman needs or wants it. Lifestyle adjustments like keeping the room cool, using layered bedding you can kick off, and avoiding alcohol and spicy food before bed can reduce the frequency.
Medications That Cause Sweating
Antidepressants are one of the most common medication-related causes of night sweats. SSRIs and SNRIs, the two most widely prescribed classes of antidepressants, cause excessive sweating in roughly 7 to 19% of people who take them, depending on the specific drug. This happens because these medications affect serotonin signaling, which plays a role in temperature regulation.
Other medications that commonly trigger night sweats include hormone-blocking drugs used in cancer treatment, steroids, blood pressure medications, and over-the-counter fever reducers like acetaminophen and aspirin (which work by lowering your set-point temperature, prompting your body to sweat off the “extra” heat). If your night sweats started around the same time you began a new medication, that connection is worth raising with your prescriber. Adjusting the dose or switching to a different drug often resolves the problem.
Sleep Apnea and Night Sweats
This is a connection many people don’t expect. Obstructive sleep apnea, where your airway repeatedly collapses during sleep, is strongly linked to night sweats. A study published in the European Respiratory Journal found that 31% of people with untreated sleep apnea reported frequent night sweats (three or more times per week), compared to just 11% of the general population. That threefold difference held up even after accounting for weight, age, smoking, and other health conditions.
The mechanism likely involves the stress your body goes through during apnea episodes. Each time your airway closes, your oxygen drops and your nervous system kicks into a fight-or-flight response, which activates sweat glands. The encouraging finding: once people started using a CPAP machine effectively, their sweating dropped back down to general population levels. If you snore loudly, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea is worth investigating as the cause of your sweating.
Thyroid Problems
An overactive thyroid (hyperthyroidism) essentially speeds up your metabolism. Excess thyroid hormone increases your basal metabolic rate, shifts your muscle fibers toward types that generate more heat, and ramps up energy expenditure throughout your body. The result is that you run hotter than normal, day and night. During sleep, when your body is trying to cool down, this extra heat production can trigger sweating.
Other signs of an overactive thyroid include unexplained weight loss, a racing or irregular heartbeat, anxiety, trembling hands, and feeling warm when others are comfortable. A simple blood test can confirm or rule this out.
Low Blood Sugar During Sleep
If you take insulin or certain diabetes medications, night sweats may signal that your blood sugar is dropping too low while you sleep. Nocturnal hypoglycemia occurs when blood glucose falls below 70 mg/dL during the night. Your body responds by releasing stress hormones to raise blood sugar, and those same hormones trigger sweating. You might also wake with a headache, feel groggy or confused, or find your sheets damp with sweat.
This can happen if you took too much insulin before bed, skipped a snack, or exercised heavily that day. If you suspect overnight lows, checking your blood sugar when you wake up sweating (or using a continuous glucose monitor) can confirm the pattern.
Infections and Immune Responses
Night sweats are a classic symptom of several infections. Tuberculosis is the textbook example, but bacterial infections like endocarditis (infection of the heart valves), abscesses, and bone infections can all cause drenching sweats during sleep. HIV, particularly in its early acute phase, commonly triggers night sweats as the immune system mounts a response. Even common viral infections can cause temporary night sweats that resolve once you recover.
The mechanism is straightforward: your immune system raises your body’s temperature set-point to fight off the infection (a fever), and when that set-point resets, your body sweats to shed the extra heat. During sleep, this cycling can produce dramatic sweating episodes.
When Night Sweats Signal Something Serious
Lymphoma and certain other cancers can cause what doctors call “drenching” night sweats, defined as sweats so heavy you need to change your bedclothes. In lymphoma specifically, night sweats are one of the “B symptoms” used in diagnosis and staging, alongside unexplained fever and significant weight loss.
Night sweats alone are rarely a sign of cancer. The vast majority of people who sweat at night have one of the more common causes listed above. But certain patterns warrant a medical evaluation: night sweats that occur regularly and disrupt your sleep, sweats accompanied by unexplained weight loss or persistent fever, sweats paired with pain in a specific area or a lingering cough, or sweats that begin months or years after menopause symptoms had already ended. These combinations raise the index of concern and deserve bloodwork and a thorough exam.
Narrowing Down Your Cause
Because the list of possibilities is long, the most useful thing you can do is notice patterns. Track when the sweating started and whether anything changed around that time: a new medication, weight gain, increased stress, a shift in your menstrual cycle. Note how often it happens, whether it’s localized (head and chest vs. whole body), and whether you have any daytime symptoms like fatigue, weight changes, or feeling overheated.
If cooling your bedroom and switching to lighter bedding doesn’t help, and the sweating is happening several times a week, a visit to your doctor is the logical next step. Basic blood tests can screen for thyroid problems, infections, blood sugar issues, and markers of inflammation. A sleep study can identify or rule out sleep apnea. In most cases, once the underlying cause is identified, effective treatment exists.