Night Sweats: Why Do I Sweat When I Sleep?

We’ve all been there — you wake up in the middle of the night covered in sweat. You pull all the sheets off your body, desperate for some cool air. This happens night after night and you’re ready to figure out how to solve it.

Usually, when you experience night sweats, body temperature is to blame. Elevated body temperature might be the result of wearing too many clothes, or could be related to a fever. However, some common causes of night sweats can be related to medical conditions.

How do you know when sweating in your sleep is a problem? If you have so much sweat that you are changing your pajamas in the middle of the night and changing your sheets multiple times a week, it’s worth looking into potential causes of sleep sweating.

In some cases, long-lasting episodes of night sweats are the first indication that someone has a serious health condition. Let’s take a look at some common causes of night sweats, or nocturnal hyperhidrosis, and what they mean.

What Are Night Sweats?

Night sweats are common. Most people have experienced night sweats at some point in their lifetime. In one study of 2,000 people who visited a healthcare provider, 41% reported experiencing night sweats within the past month.

In most cases, night sweats are a harmless and simple way your body cools itself. Without sweat, our bodies would overheat and we wouldn’t survive. However, true night sweats are more than simple thermoregulation and most likely due to a medical condition.

Why Do I Sweat When I Sleep?

If you’re wondering if you have a problem with sleep sweating, it’s probably an issue you’ve dealt with more than once. It can be scary to think that your night sweating is caused by a serious medical condition. The good news is that in most cases, the diagnosis is simple.

Body Temperature and Excessive Sweating

You might be sweating at night because your sleeping environment is too warm.

Where you set your thermostat can impact the quality of your sleep. Thermoregulation, or how your body heats and cools itself, is affected by heavy bedding and clothing.

Do you layer on the pajamas? What about sheets, blankets, and comforters? Many people mistakenly believe that they will sleep better when the room is a little warm.

Body temperature is naturally lower at night, thanks to your circadian rhythm. If you insulate yourself too much with blankets and sleepwear, you might not sleep as well. If a room gets stuffy or hot, you might find yourself waking frequently. If you need a blanket, like plenty of sleepers do, to feel comfortable, try looking specifically for a blanket that won’t make you hot.

Sleep experts recommend keeping your sleeping environment at a cool 60-67 degrees Fahrenheit. This cool room temperature helps you get to sleep and promotes restful sleep. Your core body temperature drops one to two degrees before you sleep. Cooling the room can tell your body it’s time for bed. The cool temperature also triggers the production of melatonin, the hormone that helps you sleep.

Once asleep, a cooler room temperature helps you stay in REM sleep longer. If the room is warm, it could disturb you and wake you from REM sleep. Your body is not disturbed by cold temperatures when you sleep, so you are less likely to wake from REM sleep when your environment is cool.

Medical Conditions

Do you sweat through your sleepwear and sheets in the middle of winter without the heater on? Do you need to wake in the night to shower because you are so sweaty? If so, your excessive sweating may be caused by a medical condition. But, if your night sweats occur only occasionally, there may not be cause for concern.

Have you soaked your bed every night for over a month? If so, it’s worthy of a checkup where your provider will likely order tests. Many providers get concerned about night sweats that last beyond eight weeks.

When you visit your internal medicine doctor or primary care provider, it helps to know some causes of night sweats that are not related to body temperature. You can discuss the following underlying medical conditions with them:

1. Fever 

Fever is your body’s defense against invading pathogens. By heating up the body, your immune system can destroy germs, and sweating occurs in the process. People with a fever often feel better and their temperature drops after an episode of sweating. Over-the-counter medications can be used to reduce fever.

2. Bacterial infection

Your provider will assess you for bacterial infection by taking a detailed medical history.

Risk factors for bacterial infection include:

• IV catheter use
• History of inflammation of the heart valves (endocarditis)
• Recent dental work
• Suppressed immune system

If you have any pain you can pinpoint, along with a fever, that may be a sign of infection. Infections include endocarditis, bacteremia, osteomyelitis, pyogenic abscess, and spinal infection.

3. Carcinoid syndrome

Carcinoid syndrome is caused by tumors that line the digestive tract. Symptoms of carcinoid syndrome include:

• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Constipation
• Feeling of warmth in your face and neck that can lead to night sweats

4. Lymphoma

Symptoms of lymphoma include:

• Unexplained weight loss
• Fatigue
• Itching of the skin
• Enlarged lymph nodes

Enlarged lymph nodes should be evaluated by a healthcare provider as soon as possible.

5. Hormonal changes, hormone disorders, hormone therapy, and hormone replacement

Hormonal changes are one of the most common causes of night sweats. Lots of hormones work together to regulate your body temperature. When these hormones fluctuate, excessive sweating can occur.

Women experiencing perimenopause and menopause symptoms may experience hot flashes. Many women who are immediately postpartum also experience hot flashes in the first few days after birth.

Hyperthyroidism, in particular, is linked to excessive sweating because the thyroid gland controls thermoregulation.

6. Some sleep disorders

Obstructive sleep apnea is the most dangerous sleep disorder associated with night sweats. People with obstructive sleep apnea struggle to breathe while they are sleeping. This struggle to breathe is much like running a race or climbing a mountain.

Sleep apnea is stressful for the heart and leads to sweating just like exercise does. Obstructive sleep apnea is a dangerous condition that requires treatment by a sleep specialist.

Many sleep disorders like insomnia cause people to be light sleepers. People who do not reach deep sleep may wake more often and notice temperature or sweating more often than people who sleep deeply.

7. Medications

Many medications cause excessive sweating as a side effect. When these medications are taken before bed, night sweating can occur.

• Antidepressants are the most common cause of sweating from medication.
• Cholinergic medications can cause increased sweating.
• Hypoglycemic drugs are used to lower blood sugar. When a person experiences very low blood sugar, excessive sweating can be a result.

When to Seek Treatment for Night Sweats

Usually, the question that follows, “Why do I sweat in my sleep?” is, “What should I do about it?”

When night sweating is mild, it can usually be managed with lifestyle changes. Sleep hygiene can improve the quality of your sleep. When sleep quality is improved, you may not be as easily woken by body temperature or sweating.

Going to bed at the same time and waking at the same time each day are the first steps toward better sleep hygiene. Keep your bedroom cool and free from lights and screens. Avoid caffeine afternoon. Make a to-do list for the next day so you can feel relaxed at bedtime.

Seeing a Doctor for Night Sweats

Unfortunately, sleep hygiene doesn’t always improve night sweats. When the sweating is so intense that clothes and sheets need to be changed, it’s time to seek treatment from a healthcare provider.

Your clinician will do a full workup to determine the cause of your sleep sweating. The workup will include taking a detailed medical history, running tests, and possibly conducting a sleep study.

If all medical causes of night sweats are ruled out, you may be diagnosed with idiopathic hyperhidrosis. This diagnosis means your body produces too much sweat without a medical cause.

How Can You Stop Night Sweats?

If your night sweating has no medical cause, you can reduce sweating by avoiding triggers.

• The most obvious trigger is temperature: Keep the thermostat low if possible. But also invest in breathable sheets and the best mattress for hot sleepers to make sure your sleeping surface isn’t making matters worse.
• Avoid eating spicy food right before bed. If you need a late-night treat, try sleep-promoting snacks.
• Reduce stress. Stress is a trigger for many people with excessive sweating. While stress is impossible to avoid entirely, you can take measures to avoid stress at night or mitigate its effect on your quality of life.
• Stick to conversational topics that are not stressful before bed. Avoid watching or reading the news in the few hours before bed. Wind down with breathing exercises or book after you climb into bed.
• Exercising and maintaining a healthy weight can reduce sweating. Many people who are diagnosed with hyperhidrosis find that they need to be more active. Reducing BMI through exercise and diet can reduce excess sweating.

Are You Ready to Stop Sweating the Night Away?

Night sweats are common — almost half of all people have experienced them recently. Usually, night sweats are caused by your body’s attempt to regulate your body temperature. When night sweating is related to a medical condition, it could be related to fever, infection, carcinoid syndrome, lymphoma, or a sleep disorder. In many cases, night sweats are a side effect of certain medications.

If there is no identifiable cause for your night sweats, making changes to your sleep routine and sleep hygiene may be helpful. Seeing your healthcare provider will help you identify the cause of your night sweats.