Night sweats have a wide range of causes, from hormonal shifts and medications to infections and sleep disorders. Waking up drenched in sweat once in a while, especially in a warm room, is usually nothing to worry about. But when it happens repeatedly and your sleeping environment isn’t the problem, something else is going on in your body. Here are 10 common causes worth knowing about.
1. Menopause and Perimenopause
Hormonal changes around menopause are one of the most common reasons people experience night sweats. As estrogen levels fluctuate and decline, the brain’s internal thermostat becomes more sensitive, triggering sudden waves of heat and sweating even when the room is cool. About 20% of women report night sweats five to ten years before their final menstrual period. That number climbs sharply to around 40% right around the time periods stop for good.
These episodes aren’t brief. Longitudinal data from the Study of Women’s Health Across the Nation (SWAN) estimated that hot flashes and night sweats last an average of 7.4 years, while the Penn Ovarian Aging study put the average closer to 10 years. The intensity and frequency vary widely from person to person, but for many women, night sweats are the symptom that disrupts sleep the most during this transition.
2. Medications
Several common medications list excessive sweating as a side effect, and this often shows up most noticeably at night. Antidepressants, particularly SSRIs like citalopram, escitalopram, fluoxetine, and paroxetine, are well-known culprits. They affect serotonin signaling in the part of the brain that regulates body temperature, which can trigger sweating episodes during sleep.
Other drug classes associated with night sweats include blood pressure medications, hormone therapies, steroids, and some over-the-counter fever reducers when taken regularly. If your night sweats started shortly after beginning a new medication or changing a dose, the timing is a strong clue. Switching to a different medication in the same class often resolves the problem.
3. Infections
Night sweats are a hallmark symptom of tuberculosis, so much so that “night sweats” became a defining feature of the disease historically. The reason TB produces sweating specifically at night ties into your body’s natural rhythms: body temperature dips to its lowest point in the predawn hours, and cortisol, a hormone that suppresses immune-driven fever, drops to its lowest levels overnight. With less cortisol keeping inflammation in check, the immune response to TB flares during sleep, producing fever and drenching sweats.
TB isn’t the only infection that causes this pattern. Bacterial endocarditis (an infection of the heart valves), HIV, abscesses, and fungal infections can all produce recurring night sweats. Infections tend to cause additional symptoms like fever during the day, fatigue, and unintentional weight loss.
4. Lymphoma and Other Cancers
Night sweats are one of the classic “B symptoms” of lymphoma, alongside unexplained weight loss and recurring fevers. Patients with Hodgkin or non-Hodgkin lymphoma often describe these as drenching night sweats, the kind that soak through pajamas and sheets, not just light dampness. The sweats result from the body’s immune system reacting to the cancer and from inflammatory chemicals the tumor cells release.
Other cancers can cause night sweats too, including leukemia and certain solid tumors. When night sweats are cancer-related, they’re typically persistent, happening most nights for weeks, and accompanied by other warning signs like swollen lymph nodes in the neck, armpits, or groin, persistent fatigue, or losing weight without trying.
5. Obstructive Sleep Apnea
Sleep apnea is an underrecognized cause of night sweats. An Icelandic study found that about 31% of men and 33% of women with obstructive sleep apnea reported frequent night sweats (three or more times per week), compared to only 9% of men and 12% of women in the general population. When your airway repeatedly closes during sleep, your body goes into a stress response, spiking adrenaline and raising your heart rate. That stress activation triggers sweating.
If your night sweats come alongside loud snoring, gasping awake, morning headaches, or daytime exhaustion, sleep apnea is worth investigating. Treating the apnea, usually with a CPAP device, often resolves the sweating.
6. Anxiety and Stress
Your nervous system doesn’t fully shut off during sleep, and if you’re dealing with chronic anxiety or high stress levels, your body can trigger a sweat response overnight. The mechanism is straightforward: stress activates the same nerve pathways that control your sweat glands. Cholinergic nerve fibers, the primary trigger for eccrine sweat glands across your whole body, can fire during periods of psychological stress even while you’re asleep.
Nocturnal panic attacks are a more dramatic version of this. Some people wake suddenly with a racing heart, shortness of breath, and heavy sweating, sometimes without remembering a nightmare or feeling consciously anxious. The sweating from anxiety tends to be most noticeable on the palms, soles, face, and underarms, though it can involve the entire body.
7. Hyperthyroidism
An overactive thyroid gland speeds up your metabolism, which raises your baseline body temperature and makes you sweat more easily, day and night. Your thyroid essentially sets the pace for how fast your cells burn energy, and when it’s overproducing hormones, your internal thermostat runs hot. Night sweats from hyperthyroidism usually come with other signs: unexplained weight loss despite a normal or increased appetite, a rapid or irregular heartbeat, trembling hands, and feeling wired or anxious.
8. Low Blood Sugar
When blood sugar drops too low, especially overnight, your body releases adrenaline to mobilize stored glucose. That adrenaline surge causes sweating, shakiness, and a racing heart. This is most common in people with diabetes who take insulin or certain oral medications, but it can happen in anyone whose blood sugar dips unusually low during the night. You might wake up drenched in sweat, feeling shaky or hungry, or with a headache in the morning.
If you have diabetes and notice a pattern of night sweats, checking your blood sugar when you wake up sweating can help confirm whether low glucose is the cause.
9. Hormone-Producing Tumors
Rare tumors of the adrenal glands, called pheochromocytomas, produce excess adrenaline and related hormones. This leads to episodes of high blood pressure, pounding headaches, irregular heartbeat, and excessive sweating that can strike without warning, including during sleep. These episodes are sometimes called “paroxysmal attacks” because they come in sudden bursts.
Pheochromocytomas are uncommon, but they’re worth knowing about because the symptoms can mimic anxiety or panic attacks. The key difference is the severe blood pressure spikes. Other hormone-producing tumors, like carcinoid tumors, can also cause flushing and sweating.
10. Autonomic Nervous System Disorders
The autonomic nervous system controls sweating, heart rate, blood pressure, and other functions you don’t consciously manage. When this system is damaged or dysregulated, sweating can become unpredictable and excessive. Spinal cord injuries are one clear example: damage above the mid-chest level can cause a condition called autonomic dysreflexia, where a stimulus below the injury triggers an exaggerated sympathetic response, producing profuse sweating and flushing above the injury site along with dangerous blood pressure spikes.
Other conditions that disrupt autonomic function, including diabetes-related nerve damage, Parkinson’s disease, and certain autoimmune conditions, can also cause abnormal sweating patterns at night. In these cases, the sweating tends to be part of a broader picture of autonomic symptoms like lightheadedness on standing, digestive issues, or difficulty regulating heart rate.
When Night Sweats Signal Something Serious
Occasional night sweats after a spicy meal, a warm bedroom, or a stressful day are normal. The pattern that warrants attention is persistent, drenching sweats that happen repeatedly over weeks and can’t be explained by your environment. Pay particular attention if your night sweats come alongside unexplained weight loss, fevers, swollen lymph nodes, or persistent fatigue, as this combination raises the concern for infection or malignancy.
A useful first step is to review any medications you’re taking and note whether the sweats started around the same time as a new prescription. If you snore heavily or wake gasping, a sleep study can rule out apnea. For women in their 40s or 50s, the timing relative to menstrual cycle changes often points to perimenopause. When the cause isn’t obvious, basic blood work checking thyroid function, blood sugar, inflammatory markers, and blood counts can help narrow down the list.