Night Sweats: When They Can Be a Cancer Sign

This page is for anyone who has heavy night sweats and wonders if they could be a sign of cancer. It covers what counts as a drenching sweat, the common causes, and what a doctor may check.

A little sweating at night is normal, especially in a warm room or under heavy blankets. Heavy, drenching night sweats are different. They soak your sheets and pajamas and keep happening, night after night. This kind of sweating can occasionally be a sign of cancer, most often a blood cancer. It has many other causes too, and most people with night sweats do not have cancer.

Doctors care about the pattern, not one bad night. A night sweat worth mentioning is one that happens repeatedly. It soaks through your clothes or bedding. It is not explained by a hot room, heavy blankets, or a fever from a cold. Waking up and needing to change your shirt or sheets is the kind of detail your doctor wants to hear.

Night sweats are most linked to lymphoma, a cancer of the lymph system, and leukemia, a cancer of the blood and bone marrow. In lymphoma, doctors track three symptoms together: fever with no clear cause, drenching night sweats, and weight loss you did not try to lose. Doctors call this group "B symptoms."

Night sweats have many everyday causes, including:

• Menopause.
• Infections and fever.
• Low blood sugar.
• Anxiety.
• Alcohol.
• A warm bedroom.
• Certain medicines, including some medicines for mental health conditions and fever-reducing drugs.

Your doctor starts with questions: how often the sweats happen, how long they have gone on, and whether you also have fever, weight loss, or swollen lymph nodes. Lymph nodes are small, bean-shaped glands in your neck, underarms, or groin that are part of your immune system. Bloodwork, such as a complete blood count, is common early on. It can point toward infection or a blood cancer. If your doctor feels a swollen lymph node or sees something concerning on a scan, the next step is usually a biopsy. That means removing a small piece of tissue to look at under a microscope. Preparing the tissue slides takes several days. The National Cancer Institute says the pathologist usually sends the report to your doctor within 10 days of the biopsy. Special tests can add time. If lymphoma seems likely, imaging such as a CT or PET scan can show which lymph node areas are involved.

Before your appointment, jot down how many nights a week the sweats happen, how long this has gone on, and whether you change your sheets or clothes. Note any fevers, weight change, or new lumps. Bring a list of your medicines too, since some can cause night sweats as a side effect. This short record often speeds up the visit, because it gives your doctor a clear pattern to work with instead of a vague memory.

A normal blood count or a clear physical exam is reassuring, but it does not rule out every possible cause. If night sweats continue after an initial workup is normal, tell your doctor rather than assuming it is nothing. Symptoms that persist deserve a second look, especially once new symptoms join them.

Night sweats on their own almost never need urgent care. It is the company they keep that matters.

• Call your care team straight away, at any hour, if you have a temperature of 100.4°F (38°C) or higher and you are having chemotherapy. CDC says a fever during chemotherapy is a medical emergency and to call your doctor right away. Go to the emergency room if needed, and tell staff you are having chemotherapy.
• Call 911 or go to the ER if sweating comes with chest pain or pressure, or trouble breathing. Do not drive yourself.
• Call your care team the same day if you are not in treatment and soaking sweats arrive with a temperature of 100.4°F (38°C) or higher that you cannot explain, or if you feel genuinely unwell rather than just tired.
• Call your care team within a day or two if the sweats keep soaking your sheets week after week, or a painless swollen gland in your neck, underarm, or groin turns up alongside them, or your weight is falling without you trying.

• Could my night sweats be related to an infection or a blood cancer?
• Should my lymph nodes and blood counts be checked?
• What other symptoms should I watch for?
• Could a medicine I take be causing this?

• National Cancer Institute — Adult Non-Hodgkin Lymphoma Treatment (PDQ)
• American Cancer Society — Signs and Symptoms of Cancer
• MedlinePlus — Sweating
• National Cancer Institute — Pathology Reports