Waking up drenched in sweat is surprisingly common, and the causes range from a too-warm bedroom to hormonal shifts, medications, and occasionally something more serious. True night sweats go beyond feeling a little warm under the covers. They soak through your pajamas and sheets regardless of the room temperature, and when they keep happening, your body is telling you something worth investigating.
Night Sweats vs. Sleeping Hot
There’s a meaningful difference between overheating at night and clinical night sweats. If you kick off the blankets and the sweating stops, your bedroom is probably too warm or your bedding is trapping heat. Night sweats, by contrast, drench your clothing and bedding even in a cool room. They happen because something internal, whether hormonal, metabolic, or neurological, has thrown off your body’s temperature regulation. That distinction matters because it changes what you should do about it.
Your Bedroom and Habits May Be the Simplest Explanation
Before looking at medical causes, it’s worth ruling out the obvious. Alcohol, caffeine, and spicy foods before bed can all raise your core body temperature enough to trigger heavy sweating overnight. Alcohol is a particularly common culprit because it dilates blood vessels near the skin’s surface, creating a rush of heat as your body processes it.
Synthetic sheets, memory foam mattresses, and heavy comforters trap heat against your body. Switching to lightweight cotton or linen pajamas and breathable, layered bedding you can peel off during the night makes a real difference for many people. Keeping your bedroom between 60 and 67°F (15 to 19°C) is the range most sleep experts recommend.
If you’ve addressed all of that and you’re still waking up soaked, something else is going on.
Hormonal Changes Are the Most Common Medical Cause
Fluctuating estrogen and progesterone levels are the single most frequent medical reason for night sweats. These hormones help your brain regulate body temperature. When their levels rise or fall sharply, as happens during perimenopause, menopause, pregnancy, or certain phases of the menstrual cycle, your brain’s internal thermostat essentially malfunctions. It misreads your body temperature as too high and triggers a sweating response to cool you down, even though you weren’t actually overheated.
For people in perimenopause or menopause, night sweats often come in waves over months or years. They can start years before periods stop entirely and may persist for several years afterward. Testosterone changes can also cause night sweats in men, particularly during andropause (the gradual decline in testosterone that occurs with aging) or as a side effect of hormone-blocking treatments for prostate cancer.
Medications That Trigger Sweating
A wide range of medications list night sweats as a side effect, and this is one of the most overlooked causes. The most common offenders include:
- Antidepressants, particularly SSRIs, are among the most frequently reported causes of medication-related night sweats
- Hormone therapy and drugs that affect sex hormones
- Blood pressure medications, including certain beta blockers and angiotensin receptor blockers
- Diabetes medications that lower blood sugar, including insulin and oral agents
- Steroids (corticosteroids)
- Pain relievers, including over-the-counter anti-inflammatory drugs and opioid-based medications
- Thyroid supplements and decongestants
If your night sweats started or worsened around the time you began a new medication, that timing is a strong clue. Don’t stop taking a prescribed medication on your own, but it’s worth bringing up the connection at your next appointment. Sometimes a dosage adjustment or switching to a different drug in the same class resolves the problem.
Sleep Apnea and Night Sweats
This connection surprises most people. A large Icelandic study found that about 31% of men and 33% of women with obstructive sleep apnea experienced frequent night sweats (three or more times per week), compared to roughly 9% of men and 12% of women in the general population. That’s nearly a threefold increase.
Sleep apnea causes your airway to repeatedly close during sleep, dropping your oxygen levels and forcing your body into a stress response. Your nervous system kicks into high gear to reopen the airway, and one byproduct of that activation is sweating. The encouraging finding: both sweating and elevated blood pressure decreased when patients were treated with a CPAP machine. If you snore heavily, wake up gasping, or feel exhausted despite a full night’s sleep, sleep apnea is worth investigating as the root cause of your sweating.
Infections and Immune Responses
Your body raises its core temperature to fight infection, and sweating is how it brings that temperature back down. Night sweats are a hallmark of tuberculosis, but they also occur with more common infections like the flu, COVID-19, bacterial infections, and endocarditis (an infection of the heart valves). HIV can cause persistent night sweats, particularly in earlier stages before diagnosis.
Infection-related night sweats usually come alongside other symptoms: fever during the day, body aches, fatigue, or feeling generally unwell. If your sweating started suddenly and you feel sick in other ways, an active infection is high on the list of possibilities.
When Night Sweats Signal Something Serious
Drenching night sweats that soak through your clothes and bedding are considered one of the “B symptoms” of lymphoma, a cancer of the lymphatic system. Moffitt Cancer Center describes the pattern specifically: profuse sweating that soaks clothing and bedding, occurring independently of room temperature or physical exertion. This type of sweating tends to be persistent and gets worse over time rather than coming and going.
Night sweats alone are rarely cancer. But when they show up alongside unexplained weight loss (losing more than 10% of your body weight without trying), persistent fevers, swollen lymph nodes that don’t go away, or severe fatigue, that combination warrants prompt evaluation. Leukemia and certain other cancers can also produce night sweats through similar mechanisms.
Other serious but less common causes include hyperthyroidism (an overactive thyroid), which speeds up your metabolism and raises body temperature, and certain autoimmune conditions that trigger inflammatory responses during sleep.
Anxiety and Stress
Chronic stress and anxiety disorders activate your sympathetic nervous system, the same fight-or-flight system that triggers sweating during a daytime panic attack. This activation doesn’t always shut off when you fall asleep. People with generalized anxiety, PTSD, or high baseline stress levels often experience night sweats as part of a broader pattern of disrupted sleep, racing thoughts, and physical tension. Nightmares and stress dreams can also trigger acute sweating episodes.
What to Pay Attention To
Keeping a simple log for a week or two helps narrow down the cause. Note what you ate and drank before bed, what medications you took, what the room temperature was, and how drenched you actually got. Track whether you had a fever, felt anxious, or noticed anything else unusual. Patterns emerge quickly.
Night sweats that happen once during a stressful week or after a night of drinking are generally not concerning. Night sweats that persist for several weeks, happen multiple times per week, soak through your bedding, or come with other symptoms like weight loss, fever, or new lumps deserve a proper workup. A basic evaluation typically involves blood tests to check thyroid function, blood sugar, hormone levels, and markers of infection or inflammation. Depending on your other symptoms and risk factors, your provider might also recommend imaging or a sleep study.