Night sweats have dozens of possible causes, ranging from a bedroom that’s too warm to hormonal shifts, medications, infections, and occasionally something more serious like lymphoma. Most cases trace back to something treatable or manageable once you identify the trigger. Here’s a breakdown of the most common and important causes.
Your Bedroom May Be the Simplest Explanation
Before looking at medical causes, it’s worth ruling out the obvious. Your body temperature naturally dips during sleep, and if your environment fights that process, you’ll sweat. Sleep experts recommend keeping your bedroom between 60 and 67°F (15 to 19°C). Anything above 70°F is considered too hot for quality sleep. Heavy blankets, memory foam mattresses that trap heat, and synthetic sleepwear can all push your body past its comfort zone. Alcohol close to bedtime also dilates blood vessels and raises skin temperature, which can trigger sweating even in a cool room.
Hormonal Changes During Menopause
Menopause is one of the most common medical causes of night sweats. Declining and fluctuating estrogen levels during perimenopause disrupt the brain’s temperature-regulation system. Estrogen influences several neural circuits that control how your body senses and responds to heat. When those signals become unreliable, your brain can misread normal body temperature as too high and launch a cooling response: blood vessels near the skin dilate, your heart rate increases, and sweat glands activate. These vasomotor symptoms (hot flashes during the day, night sweats at night) affect up to 80% of women going through menopause and can persist for years.
Night sweats can also occur during other hormonal transitions, including puberty, pregnancy, and the days before a menstrual period, though they’re typically less severe than menopausal episodes.
Medications, Especially Antidepressants
Several common medications list night sweats as a side effect, but antidepressants are the most frequent culprits. Excessive sweating occurs in roughly 10% of people taking SSRIs and 5 to 20% of those on SNRIs. The sweating can happen day or night, but many people notice it most during sleep when they wake up damp.
Other medications that commonly cause night sweats include hormone therapy drugs, steroids, blood pressure medications, and some diabetes treatments. If your night sweats started around the same time as a new prescription, that connection is worth exploring with your prescriber. Stopping or switching a medication often resolves the problem.
Low Blood Sugar During Sleep
People with diabetes, particularly those using insulin or certain oral medications, can experience drops in blood sugar overnight. When blood sugar falls too low, your body releases adrenaline and related stress hormones to push it back up. That surge causes sweating, a rapid heartbeat, trembling, and anxiety. You might wake up drenched and shaky without immediately understanding why.
Nocturnal hypoglycemia is more common than many people realize because mild episodes can happen without fully waking you. If you have diabetes and notice unexplained night sweats, checking your blood sugar when you wake up sweating (or wearing a continuous glucose monitor overnight) can confirm whether low blood sugar is the cause.
Infections and Immune Responses
Infections are a well-known trigger for night sweats. Tuberculosis is the classic example, but bacterial infections of the heart valves, bone infections, abscesses, and HIV can all cause drenching nocturnal sweating. Even common viral illnesses like the flu can temporarily cause night sweats as your immune system ramps up its response.
The mechanism likely involves immune signaling molecules called cytokines, which your body releases to fight infection. These molecules also affect the brain’s thermostat, producing fever that tends to spike and break during the night. As the fever breaks, sweating follows. Infections that cause persistent night sweats, lasting weeks rather than days, deserve prompt medical attention.
Sleep Apnea
Obstructive sleep apnea is an underrecognized cause of night sweats. In one study, 31% of people with sleep apnea reported frequent night sweats (three or more times per week), compared to just 11% of the general population. The repeated drops in oxygen and surges of stress hormones that happen each time your airway closes can trigger sweating throughout the night.
If your night sweats come with loud snoring, gasping during sleep, or persistent daytime fatigue, sleep apnea is worth investigating. Treating the apnea, typically with a CPAP machine or oral device, often resolves the sweating.
Lymphoma and Other Cancers
Night sweats are one of the three “B symptoms” used to evaluate lymphoma, alongside unexplained fever above 100.4°F and unintentional weight loss of more than 10% of body weight within six months. The night sweats associated with lymphoma are distinctive: they’re drenching, often requiring you to change your sheets or clothes, and they persist night after night.
Other cancers can cause night sweats too, but lymphoma (both Hodgkin and non-Hodgkin types) is the malignancy most strongly associated with them. The presence of B symptoms in lymphoma patients indicates a worse prognosis and changes treatment decisions, which is why oncologists specifically ask about them.
Cancer-related night sweats are rare compared to other causes on this list, but certain red flags should prompt a medical evaluation. These include night sweats that persist for weeks, unexplained weight loss of more than 5% in six to twelve months, swollen lymph nodes that don’t go away after four to six weeks, easy bruising or bleeding, and persistent fatigue. A combination of drenching sweats, fever, and weight loss is particularly concerning.
Thyroid and Other Endocrine Disorders
An overactive thyroid revs up your metabolism, raising your baseline body temperature and making you sweat more easily, including at night. Pheochromocytoma, a rare tumor of the adrenal gland, floods your body with adrenaline and can cause dramatic sweating episodes. Carcinoid tumors, which release hormones into the bloodstream, can produce similar flushing and sweating.
These endocrine causes are far less common than menopause or medication effects, but they produce persistent, often worsening symptoms that don’t resolve on their own.
Anxiety and Stress
Your nervous system doesn’t fully shut off during sleep. If you’re going through a period of high stress or have an anxiety disorder, elevated levels of stress hormones can activate your sweat glands overnight. Nightmares and panic attacks during sleep can also trigger sudden sweating episodes. Stress-related night sweats tend to come and go with life circumstances and often improve with better sleep habits, stress management, or treatment for the underlying anxiety.
Neurological Conditions
Conditions that affect the autonomic nervous system, the network that controls involuntary functions like heart rate, blood pressure, and sweating, can cause abnormal sweating patterns. Spinal cord injuries are one example. In autonomic dysreflexia, a dangerous spike in blood pressure can trigger profuse sweating above the level of injury while the skin below stays cold and clammy. Parkinson’s disease, stroke, and some forms of neuropathy can also disrupt normal sweat regulation.
When No Cause Is Found
In some cases, a thorough workup turns up nothing. Primary (idiopathic) hyperhidrosis is a condition where excessive sweating occurs without any identifiable underlying disease. It typically starts in childhood or puberty and often runs in families. The sweating usually affects the palms, soles, underarms, or face during the day, but it can also disrupt sleep. If secondary causes like infections, endocrine disorders, and neurological conditions have been ruled out through blood work and imaging, idiopathic hyperhidrosis becomes the working diagnosis.