Ask a Doctor: Why do I get night sweats?

A stethoscope sits on an examination table in an exam room at a Community Clinic health center in Takoma Park, Md. (Bloomberg photo by Andrew Harrer)

Q: Why do I sweat in my sleep? Is there something wrong with me?

A: Night sweats are common, and a solution may be straightforward. But there are a few more concerning causes to keep in mind.

We often think of normal human body temperature to be 98.6 degrees Fahrenheit (37 degrees Celsius), but that temperature varies over a 24-hour cycle with our circadian rhythm. Just before we go to sleep, our body temperature starts to fall and ultimately reaches a nadir of about 97.7 degrees Fahrenheit around three hours before we wake up.

This is a minimal drop, but to keep the body at that temperature, many people commonly compensate by sweating at night – especially if the external temperature is too hot.

Solutions include lowering the bedroom temperature to 60 to 67 degrees Fahrenheit at night, the ideal ambient room temperature for sleep, according to the National Sleep Foundation, and swapping heat-trapping bedding for lightweight coverings and cooling sheets made from breathable materials such as linen or bamboo.

Evening alcohol intake can aggravate night sweating by causing our blood vessels to dilate (also why some people experience “flushing” while imbibing). This makes our skin feel warmer, triggering sweating. Smoking, too, leads to sweating through the effects of nicotine on the nerves responsible for activating our sweat glands. Cutting back or stopping these behaviors can improve symptoms (though keep in mind that quitting both alcohol and smoking can temporarily worsen night sweats).

Night sweats are common, with one study showing as many as 41 percent of adults experiencing them within the prior month. While night sweats are typically not associated with worse health outcomes, if you wake up each morning completely drenched, it’s time to talk with your physician as there may be something else important going on.

Here are some examples of what your night sweats could mean:

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Fluctuations in hormones

One of the most important causes of night sweats is menopause.

Menopause is a normal part of female aging when the menstrual cycle ends, usually between the ages of 45 to 55. That transition involves a fluctuation of hormones and changes to the body, which can last several years.

Among the most classic symptoms are hot flashes with night sweats, which can affect half of all women. Hot flashes and night sweats can be hard to distinguish from one another. In general, hot flashes can occur at any time and refer to a sudden feeling of heat and flushing throughout the body, thought to be caused by sudden changes to the part of the brain responsible for managing body temperature.

They’re also associated with sweating – again, it’s a way our bodies compensate for that sensation of warmth. When hot flashes happen at night, they can manifest as sweating during sleep, the kind that may leave you soaked.

If your night sweats regularly keep you from getting adequate rest, hormone therapy may help. Studies have shown hormone therapy can decrease the frequency of these symptoms by as much as 75 percent, but treatment is associated with increased risk of certain complications such as strokes, and so it is important to discuss the pros and cons with a physician who knows your medical history.

Other hormonal issues also can cause night sweats and affect men and women alike – such as an overactive thyroid gland, or hyperthyroidism. Night sweats because of hyperthyroidism are often accompanied by other symptoms such as diarrhea, jitteriness or increased heart rate, and should be discussed with a physician promptly as there are several effective treatments.

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Medication side effect

Did you start a new medication recently? That could be the reason for your night sweats.

The most common medications associated with night sweats are anti-depressants such as selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors. Increased sweating occurs in approximately 10 to 15 percent of people taking these medications, and if the night sweats are intolerable, switching to a different class may be a good idea.

Other drugs such as albuterol, commonly taken for asthma, and calcium channel blockers, used for high blood pressure, can also lead to symptoms.

A more dangerous scenario is if you have diabetes and take insulin before bedtime or other anti-hyperglycemic medications. In these cases, night sweats may be a sign of low blood sugar. If that happens, check your levels at the time of symptoms, and if low, discuss possibly adjusting your medication with your physician as soon as possible.

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Infection and cancer

Many types of infection and cancer are associated with night sweats.

– Tuberculosis or malaria: In the United States, we don’t immediately think about tuberculosis or malaria when someone has night sweats (unless you have certain risk factors such as living in or traveling to endemic areas), but globally, infections such as these are important causes of night sweats. Health-care workers or people with housing insecurity in the United States are at increased risk of tuberculosis, so it’s still on my radar for particular individuals.

– Bacterial infections, especially if present in the bloodstream, can produce night sweats and may be accompanied by fevers and other signs such as back pain or a new heart murmur depending on the source of the infection.

– Human immunodeficiency virus is a typical infection-related cause of night sweats, often also occurring with fever, whether from acute HIV infection or because of later complications such as opportunistic infections.

– Ehrlichiosis or Lyme disease can lead to night sweats, which is why I tend to ask my patients with night sweats whether they live near wooded areas or have had recent tick bites.

– Covid-19 patients may have night sweats, though they are infrequent (seen in about 2 percent of patients) and rarely are the only indication of an infection.

– Certain cancers such as Hodgkin’s lymphoma are classically associated with night sweats. This is among the most alarming reason for the symptom – and happens more frequently among younger adults, from late teens to the 30s, or in older people. People with lymphoma may have noticeably enlarged lymph nodes, and in addition to drenching night sweats, they may notice they’ve been losing weight without trying, are feeling exhausted all the time or have frequent fevers they can’t explain – all of which warrant prompt medical attention.

While many people with occasional night sweats have nothing to worry about, it’s a symptom that I take seriously when patients mention it because of these potentially worrisome, even if rare, reasons behind some cases.

When in doubt, make note of other signs and recent life events accompanying your symptoms, and talk to your physician about your concerns.

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Trisha S. Pasricha is a physician at Massachusetts General Hospital and a medical journalist.




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