Waking up drenched in sweat, even when the room isn’t particularly warm, can be both uncomfortable and confusing. Sweating during sleep is a common experience that affects people of all ages. In most cases, it’s harmless and the result of natural body processes. But in some situations, it could point to an underlying issue that needs attention. So, why do we get sweaty in our sleep?
To understand nighttime sweating, or sleep hyperhidrosis, it’s important to look at how our body regulates temperature, what factors can disrupt this balance during sleep, and how medical or environmental triggers might contribute. While occasional sweating at night is typically benign, frequent or excessive episodes may indicate something deeper.
The Body’s Thermoregulation System
The human body has a sophisticated internal system for regulating temperature, known as thermoregulation. This process keeps the body’s core temperature within a narrow, healthy range—around 98.6°F (37°C)—regardless of external conditions. The brain’s hypothalamus acts as the control center, directing the body to cool down or warm up as needed.
Sweating is one of the body’s primary cooling mechanisms. When body temperature rises above a certain threshold, sweat glands release fluid onto the skin’s surface. As this fluid evaporates, it cools the body. During the day, we’re usually aware of sweating in response to exercise, stress, or hot weather. At night, though, the process continues largely unnoticed—unless it becomes excessive.
Natural Causes of Nighttime Sweating
There are several non-medical reasons you might sweat while sleeping. These are typically environmental or lifestyle-related and can often be resolved with simple changes.
1. Room Temperature and Bedding
One of the most common reasons for nighttime sweating is simply overheating. If your bedroom is too warm or your bedding is too heavy, your body may struggle to cool itself, resulting in sweating. Materials like flannel sheets or foam mattresses can trap heat close to the body, raising skin temperature and triggering sweat production.
2. Sleep Position and Body Heat
Sleeping in certain positions—such as curled up tightly or lying against a partner—can trap heat and reduce airflow, contributing to localized sweating. Some people naturally generate more body heat, especially during deeper stages of sleep, when the body becomes less responsive to external temperature changes.
3. Nighttime Eating or Drinking
Consuming heavy meals, alcohol, or spicy foods before bed can raise body temperature. Alcohol in particular causes blood vessels to dilate, increasing warmth and prompting the body to cool itself through sweat. Similarly, caffeine or nicotine before bed can overstimulate the nervous system, leading to restlessness and sweating.
Hormonal and Physiological Causes
There are also biological and hormonal factors that may cause sweating during sleep.
1. Hormonal Fluctuations
One of the most well-known causes of nighttime sweating—especially in women—is hormonal changes. Menopause, perimenopause, and even certain phases of the menstrual cycle can lead to hot flashes, which often occur during sleep. These hot flashes are caused by fluctuations in estrogen levels and can trigger sudden feelings of heat, flushing, and profuse sweating.
Similarly, low testosterone levels in men, often due to age or hormonal disorders, can also contribute to excessive sweating.
2. Fever and Illness
Infections or fever-causing illnesses can result in night sweats as the body fights off the pathogen. This kind of sweating is usually more intense than typical overheating and is often accompanied by chills, fatigue, or other symptoms.
Stress, Anxiety, and Nightmares
The nervous system plays a key role in regulating sweat. When a person is stressed or anxious—even while sleeping—the body can go into “fight or flight” mode, triggering a surge in adrenaline and causing sweating. People who suffer from chronic stress, anxiety disorders, or frequent nightmares are more prone to waking up sweaty.
Night terrors, common in children but possible in adults, are another cause. These intense episodes of fear during sleep can cause physical reactions like increased heart rate, heavy breathing, and sweating.
Medications and Medical Conditions
Some medications have side effects that include night sweats. These include:
Antidepressants, particularly SSRIs and SNRIs
Hormonal therapies (like estrogen or testosterone treatments)
Fever reducers such as aspirin or acetaminophen
Corticosteroids
Certain diabetes medications
Additionally, several medical conditions can cause excessive nighttime sweating. These include:
Hyperthyroidism, where an overactive thyroid increases metabolic rate and body heat
Diabetes, particularly during nighttime hypoglycemia (low blood sugar)
Gastroesophageal reflux disease (GERD), which can provoke sweating during sleep
Cancers, particularly lymphoma, which often presents with drenching night sweats
Sleep apnea, a disorder that causes pauses in breathing and frequent awakenings, can be associated with sweating as the body reacts to oxygen deprivation
When to See a Doctor
Occasional night sweating, especially if linked to room temperature or lifestyle, is generally not a cause for concern. However, you should seek medical advice if you experience:
Frequent or severe night sweats
Unexplained weight loss
Fever or persistent fatigue
Night sweats despite a cool, comfortable environment
A doctor may perform blood tests, imaging, or sleep studies to determine whether an underlying condition is contributing to your symptoms.
Managing and Preventing Night Sweats
If your night sweats are not tied to a medical issue, some simple strategies can help manage them:
Keep your bedroom cool, ideally between 60–67°F (15–19°C)
Use breathable bedding and moisture-wicking sheets
Avoid heavy or synthetic pajamas
Reduce alcohol, caffeine, and spicy food intake before bed
Practice stress-reduction techniques like mindfulness, meditation, or deep breathing
Stay hydrated to support your body’s cooling mechanisms
Conclusion
Getting sweaty in your sleep can be annoying or even alarming, but it's often the result of natural processes like thermoregulation, hormonal shifts, or environmental factors. When it happens occasionally, it’s usually nothing to worry about. But if it becomes frequent, intense, or is accompanied by other symptoms, it may point to an underlying health issue worth investigating.
Understanding the many causes of sleep-related sweating can help you take control of your environment, reduce discomfort, and ensure a more restful, dry night’s sleep.
This article was created using OpenAI’s ChatGPT on May 16, 2025 and it was personally reviewed and edited by Brandon Peters, M.D. to ensure its accuracy. This use of augmented intelligence in this way allows the creation of health information that can be trusted.