Cold sweats at night happen when your body produces sweat without the usual trigger of an overheated room or too many blankets. Unlike regular sweating from a warm environment, cold sweats involve your nervous system activating sweat glands even when your skin feels cool or clammy. The causes range from completely harmless (a stressful dream, a warm bedroom) to conditions worth investigating, like hormonal shifts, low blood sugar, medication side effects, or, less commonly, infections and cancers.
How Cold Sweats Work in the Body
Your sweat glands are controlled by the sympathetic nervous system, the same network responsible for your fight-or-flight response. Normally, sweating kicks in when your core temperature rises above the threshold set by your brain’s internal thermostat. Cold sweats bypass that process. Instead, a surge of stress hormones or a chemical signal from somewhere else in the body activates those sweat glands independently of temperature.
This is why cold sweats feel different from regular overheating. Your skin may be cool or clammy to the touch, and you may wake up shivering despite damp sheets. Anxiety, pain, hormonal fluctuations, and certain medications can all flip this switch, which is why the list of possible causes is long and varied.
Hormonal Changes and Menopause
Declining estrogen levels are one of the most common reasons for night sweats. About 75% of women going through perimenopause or menopause experience sudden, brief spikes in body temperature known as hot flashes. When these happen during sleep, they’re classified as night sweats. The mechanism is straightforward: as estrogen drops, the brain compensates by releasing other hormones that destabilize its internal thermostat, causing your body temperature to fluctuate unpredictably.
These episodes can range from mild dampness to drenching sweat that soaks through pajamas and sheets. They tend to peak in the years surrounding menopause and gradually improve, though for some women they persist for a decade or longer. Hormone-related night sweats can also affect men with declining testosterone, people undergoing cancer treatments that suppress sex hormones, and those with thyroid disorders that throw off metabolic heat regulation.
Low Blood Sugar During Sleep
If your blood sugar drops below about 70 mg/dL while you’re asleep, your body responds with a burst of adrenaline to mobilize stored glucose. That adrenaline surge triggers sweating, a racing heart, and sometimes trembling or vivid nightmares. This is called nocturnal hypoglycemia, and it’s most common in people with diabetes who take insulin or certain oral medications.
The tricky part is that you may not fully wake up during the episode. Clues that low blood sugar caused your night sweats include waking with a headache, feeling unusually groggy or irritable in the morning, or finding damp sheets without an obvious explanation. If you take diabetes medication and notice a pattern, checking your blood sugar when you wake (or using a continuous glucose monitor) can confirm whether this is the cause.
Medications That Trigger Sweating
Drug-induced sweating is actually the most common cause of secondary hyperhidrosis, meaning excessive sweating caused by something other than your body’s baseline wiring. Several widely prescribed medication classes are known culprits:
- Antidepressants: SSRIs like citalopram, escitalopram, fluoxetine, and paroxetine affect serotonin signaling in the brain’s temperature center. SNRIs like venlafaxine do the same. Older tricyclic antidepressants work through a different pathway, boosting norepinephrine levels that stimulate sweat-triggering receptors.
- Opioid pain medications: Codeine, morphine, oxycodone, fentanyl, and tramadol all cause histamine release, which in turn activates the chemical messenger that drives sweat glands.
- Steroids and thyroid medications: Prednisone, dexamethasone, and levothyroxine can disrupt the hormonal feedback loops that regulate body temperature.
- Dementia medications: Drugs like galantamine and rivastigmine directly increase levels of the neurotransmitter that activates sweat glands.
If your night sweats started or worsened after beginning a new medication, that timing is a strong clue. The sweating often appears within the first few weeks of starting a drug or after a dose increase.
Sleep Apnea
Obstructive sleep apnea, where your airway repeatedly collapses during sleep, is an underrecognized cause of night sweats. Research comparing people with sleep apnea to the general population found that 31% of those with untreated sleep apnea reported sweating three or more nights per week, compared to just 11% of the general population. The likely mechanism involves the body’s stress response to repeated oxygen drops and the physical effort of struggling to breathe.
The encouraging finding is that treatment with a CPAP machine (which keeps the airway open with gentle air pressure) reduced the rate of frequent night sweats from 33% down to about 12%, essentially matching the general population. If your night sweats come with snoring, daytime fatigue, or a partner noticing that you stop breathing during sleep, sleep apnea is worth investigating.
Anxiety and Nocturnal Panic Attacks
Stress and anxiety don’t clock out when you fall asleep. Mental effort and anxiety directly increase sweating, particularly on the palms, soles, and underarms. For some people, this extends into full nocturnal panic attacks: sudden episodes of intense fear that jolt you awake with a racing heart, profuse sweating, and difficulty breathing.
Nocturnal panic attacks produce the same physical symptoms as daytime ones, but they feel more disorienting because you wake mid-episode without context. The sweating is driven by a sudden adrenaline dump, and it can be drenching. These episodes are sometimes mistaken for heart problems or thyroid disease, and providers will typically rule out those conditions first before diagnosing panic as the cause.
Infections and Cancers
Night sweats are a classic symptom of certain infections and malignancies, though these are far less common than the causes above. Tuberculosis, endocarditis (infection of the heart valves), and HIV are the infections most associated with drenching night sweats. Among cancers, lymphoma is the one most strongly linked. Drenching night sweats are one of the hallmark “B symptoms” of lymphoma, alongside unexplained fever and significant weight loss.
The key word here is “drenching.” The night sweats associated with serious illness tend to soak through clothing and bedding, not just leave you a little damp. They also rarely show up alone. Warning signs that point toward something more serious include unintentional weight loss greater than 5% of your body weight over six to twelve months, persistent or recurring fevers, swollen lymph nodes that last more than four to six weeks, unexplained fatigue, or easy bruising and bleeding. Any combination of these alongside persistent night sweats warrants a thorough medical workup.
Your Bedroom May Be the Problem
Before assuming a medical cause, it’s worth checking the basics. Sleep experts recommend a bedroom temperature around 65°F (18.3°C) for optimal sleep, and a relative humidity between 30% and 50%. Many people sleep in rooms that are significantly warmer or more humid than this, especially with memory foam mattresses, synthetic bedding, or poor ventilation. A room that feels fine when you get into bed can become uncomfortably warm after several hours under covers.
If your night sweats are occasional, not drenching, and improve when you lower the thermostat or switch to lighter bedding, the environment is the likely explanation. Night sweats that persist regardless of bedroom conditions, happen multiple times a week, or come with other symptoms are more likely to have a medical cause worth exploring.
Secondary Causes Worth Screening For
Beyond the major categories above, several other conditions cause night sweats that are easy to test for. Hyperthyroidism (an overactive thyroid) speeds up your metabolism and generates excess heat. Diabetes can cause sweating through blood sugar swings even outside the hypoglycemic range. Parkinson’s disease disrupts the autonomic nervous system that controls sweating. Even high caffeine intake can contribute.
When night sweats are new, generalized (not limited to one body area), and worse at night specifically, providers typically start with blood tests for thyroid function and blood sugar as a basic screen. The pattern of the sweats, what accompanies them, and when they started usually narrows the list quickly.