Drenching night sweats are a common symptom of certain cancers. But other conditions, medications, and behaviors can also cause them.

Sweating is how your body cools itself. It happens to everyone throughout the day, but some people experience episodes of increased sweating at night.

Night sweats are more than just breaking a sweat because you have too many blankets on your bed. They cause you, your pajamas, and your bedding to become drenched.

If you have night sweats, your sheets and pillows typically become so saturated that you can no longer sleep on them. Some people describe an episode of night sweats as feeling as if they’ve jumped into a swimming pool. Night sweats may occur even if your room is comfortably cool.

While night sweats are a common cancer symptom, several other causes might contribute to them.

Night sweats may be an early symptom of some cancers, particularly:

However, if your night sweats are due to cancer, you’ll likely experience other symptoms, such as a fever and unexplained weight loss. When assessing lymphoma symptoms, doctors collectively refer to this group of symptoms (night sweats, fever, weight loss) as “B symptoms.”

Other cancers may also cause night sweats, including bone and liver cancer. However, night sweats may be a less common symptom in these cancers.

It’s unclear why some types of cancer cause night sweats. This may happen because your body is trying to fight the cancer. Hormone level changes may also be a cause.

When cancer causes a fever, your body may sweat excessively as it tries to cool down.

In some cases, night sweats occur due to cancer treatments such as:

Although night sweats are a symptom of some types of cancer, they can also happen for other reasons, such as:

Lifestyle factors that may cause night sweats include:

  • exercising before going to bed
  • drinking hot beverages before going to bed
  • drinking alcohol
  • eating spicy foods close to bedtime
  • setting your thermostat too high
  • a lack of air-conditioning in hot weather

If you’ve only had an episode or two of night sweats, you probably don’t need to see a doctor. Environmental or lifestyle factors are likely causes. But consider seeing a doctor if night sweats occur regularly and disrupt your sleeping habits, especially if you experience fevers, unexplained weight loss, or other symptoms.

When you call to make your appointment, a doctor may ask you to keep a medical diary in the coming days. You should use this diary to track your symptoms. Each time you experience night sweats, be sure to note what you were doing that day, the temperature in your bedroom, and what you ate or drank before going to bed.

At your appointment, the doctor will review your medical history and assess your symptoms. They may order blood tests to check your thyroid levels, blood sugar levels, and blood cell counts. The results can help them confirm a suspected diagnosis or help rule out an underlying condition.

If you think your night sweats may be a sign of cancer, discuss this with the doctor. Be honest about your symptoms and concerns, and feel free to seek a second opinion if you think your doctor isn’t properly addressing them.

Tips for your doctor’s visit

The following tips may help you have a successful conversation with your doctor about night sweats:

  • Write down a list of questions or concerns you have ahead of time and bring it to your appointment.
  • Bring a family member or friend with you for support.
  • Take notes during your appointment to help you remember your doctor’s recommendations.
  • If you don’t understand something, ask your doctor to repeat it.
  • Ask your doctor if you can record your conversation.

Treatment for night sweats depends on their cause. Night sweats caused by environmental or lifestyle factors should go away on their own once you eliminate their triggers. If infection is the cause, a doctor may prescribe antibiotics.

If night sweats occur due to perimenopause or menopause, talk with a doctor about hormone replacement therapy (HRT). Some kinds of HRT may increase your risk of developing serious conditions, such as:

You’ll need to carefully weigh the pros and cons of taking HRT against having night sweats.

If cancer turns out to be the cause of your night sweats, then your focus will shift to treating the cancer. Cancer treatments vary by type and stage. Common treatments include surgery, chemotherapy, and radiation.

Some cancer treatment drugs may cause night sweats. But as your body adjusts to the treatment, the night sweats may subside.

The off-label use of these drugs may relieve night sweats:

A small 2019 study also found that dronabinol, a synthetic form of tetrahydrocannabinol (THC) that is FDA approved to treat nausea from chemotherapy, may also help with night sweats in people with cancer.

Most people experience the discomfort of night sweats at least once, typically with no lasting problems. If you have night sweats regularly, your outlook depends on why you have them. Persistent night sweats are your body’s way of letting you know something may be wrong. Doctors can treat most causes successfully.

If cancer is causing your night sweats, they usually stop after successful cancer treatment. The earlier you seek treatment, the better your chances may be for remission. It’s important not to put off seeing your doctor.

For people with lymphoma, the presence of night sweats and other B symptoms is more significant than other symptoms and may suggest a less favorable outlook. Still, early diagnosis and treatment are vital to improving your outlook with lymphoma.

Although night sweats are a common symptom of some cancers, they’re unlikely to signify cancer, especially on their own. If you have persistent, drenching night sweats along with other symptoms, like fever and unexplained weight loss, it could be a sign of certain cancers.

Talk with a doctor about your symptoms. They can perform tests to determine the cause of your night sweats and help you determine the next best steps to manage them.