Night sweats have a wide range of causes, from a too-warm bedroom to hormonal shifts, medications, infections, and occasionally something more serious like lymphoma. Most of the time the explanation is straightforward, but persistent, drenching sweats that soak through your sheets deserve a closer look. Here’s a breakdown of the most common causes and what sets them apart.
Hormonal Changes
Hormonal shifts are the single most common medical reason for night sweats. An estimated 35% to 50% of perimenopausal women experience sudden waves of body heat with sweating and flushing that last 5 to 10 minutes, striking during the day and at night. These episodes typically continue for a year or two after menopause, though about 10% of women deal with them for years beyond that. The sweating happens because fluctuating estrogen levels throw off the brain’s internal thermostat, narrowing the temperature range your body considers “normal” and triggering a cooling response (sweating, flushing) at the slightest provocation.
Women in their late 30s to early 60s may notice night sweats before their periods become noticeably irregular, so it’s worth considering perimenopause even if your cycle still seems mostly normal.
Men aren’t exempt. Low testosterone (hypogonadism) can cause hot flashes and sweating that mirror what women experience during menopause. Other signs include low libido and erectile dysfunction. A simple early-morning blood test can check testosterone levels.
Medications
Up to 22% of people taking antidepressants develop excessive sweating as a side effect, and it frequently shows up at night. This isn’t limited to one type of antidepressant. SSRIs, SNRIs, and older tricyclic antidepressants all carry the risk. These drugs interfere with the brain’s temperature-regulation center by altering serotonin and norepinephrine signaling, which can trigger sweating even when your body doesn’t actually need to cool down.
Other medications commonly linked to night sweats include fever-reducing drugs like aspirin and acetaminophen (which can cause rebound sweating as they wear off), blood pressure medications, hormone therapies, and some diabetes treatments. If your night sweats started shortly after beginning a new prescription, that timing is a strong clue.
Low Blood Sugar at Night
If you have diabetes and wake up with damp sheets, nocturnal low blood sugar is a likely suspect. Hypoglycemia, generally defined as a blood sugar level below 70 mg/dL, triggers your body’s stress response, which includes sweating. You might not fully wake up during the episode, so the main evidence is soaked nightclothes and sheets. Other overnight symptoms can include restless sleep, vivid nightmares, and waking with a headache or feeling unusually groggy.
This is most common in people who take insulin or certain oral diabetes medications, especially if you’ve skipped a meal, exercised late in the day, or taken too high a dose.
Infections
Infections cause night sweats through a straightforward mechanism: inflammatory signals temporarily raise the set point of your body’s thermostat, producing chills and shivering that push your core temperature up. When those signals fade, the thermostat resets to normal and your body sweats to dump the excess heat. Because inflammatory activity tends to fluctuate overnight, with periodic spikes in immune-signaling molecules, the sweating often clusters during sleep.
Tuberculosis is the classic infection associated with drenching night sweats, but bacterial heart infections (endocarditis), bone infections, abscesses, and HIV can all cause them. Even a common viral illness can trigger temporary night sweats. The difference is duration: a few nights of sweating during a cold is unremarkable, while weeks of unexplained sweating alongside fever, weight loss, or fatigue points to something that needs investigation.
Thyroid and Adrenal Problems
An overactive thyroid ramps up your metabolism and heat production, making night sweats a predictable result. Other signs include anxiety, a fast or pounding heartbeat, trembling hands, unintended weight loss, heat intolerance during the day, and diarrhea. A thyroid blood test is quick and definitive.
A rarer but more dramatic cause is a pheochromocytoma, a small tumor on one of your adrenal glands that releases bursts of adrenaline-like hormones. The hallmark is episodes of intense sweating with headaches, a racing heart, and blood pressure that spikes unpredictably. During a sweating episode, your hands and feet may feel cold and look pale because the adrenaline surge constricts blood vessels in your extremities. This is uncommon but treatable once identified.
Lymphoma and Other Cancers
Night sweats are one of the three “B symptoms” used to stage lymphoma. The clinical definition is specific: drenching sweats that require you to change your bedclothes. The other two B symptoms are unexplained fever above 100.4°F and unexplained weight loss of more than 10% of your body weight over six months. Having one or more of these symptoms together changes how the cancer is classified and treated.
Night sweats from cancer are typically persistent, worsening over weeks, and accompanied by at least one of those other red-flag symptoms. Itching alone, fatigue alone, or a brief fever with an obvious infection do not count as B symptoms. If you’re experiencing severe, recurring night sweats alongside unexplained weight loss or persistent fevers, that combination warrants prompt medical evaluation.
Your Sleep Environment
Before assuming a medical cause, consider the simplest explanation: your bedroom is too warm. The ideal sleeping temperature for adults is 60 to 67°F (15 to 19°C). A room above that range, heavy blankets, or synthetic pajamas that trap heat can all produce sweating that feels dramatic but has no medical significance.
A few practical adjustments can help you rule this out or reduce sweating from any cause:
- Keep a fan nearby so you can cool down quickly if you wake up warm.
- Choose breathable fabrics for both pajamas and sheets, and adjust them seasonally.
- Skip caffeine and sugary foods close to bedtime, both of which can raise your body temperature.
How Doctors Narrow Down the Cause
Because the list of possible causes is long, doctors typically start with your history: when the sweats started, how severe they are, what medications you take, and what other symptoms you’ve noticed. The pattern of accompanying symptoms does most of the diagnostic work. Sweating plus menstrual changes in a woman in her 40s points toward perimenopause. Sweating plus anxiety, weight loss, and a fast pulse suggests a thyroid check. Sweating plus drenching episodes, fever, and weight loss raises concern for lymphoma or a chronic infection.
There’s no single “night sweat test.” Instead, your doctor picks targeted labs based on the most likely explanation: thyroid hormones, blood sugar, testosterone, infection markers, or imaging studies when something more serious is suspected. In many cases, identifying a medication side effect or confirming perimenopause is enough to explain the problem without extensive testing.