Are Night Sweats a Sign of Cancer?

This page is for people who wake up sweating and wonder whether it could be cancer. It explains what counts as a night sweat, the common causes, and when to get checked.

Most people sweat at night sometimes. The NHS draws the line in a way that is easy to apply.

It says night sweats are when you sweat so much that your night clothes and bedding are soaking wet, even though where you are sleeping is cool. It also says it is normal to sweat at night if the room or bedding is making you too hot.

So the first question is not how bad it felt. It is whether the room was cool and whether you had to change the sheets.

The NHS lists the most common causes, and none of them are cancer:

• Menopause symptoms, such as hot flashes (the NHS calls them hot flushes).
• Anxiety.
• Medicines, such as some antidepressants, steroids and painkillers.
• Low blood sugar.
• Alcohol or drug use.
• Hyperhidrosis, a harmless condition that makes someone sweat too much all the time.

It adds that sometimes the cause of night sweats is never found. Infections, including ones that build slowly, and an overactive thyroid belong on the wider list too.

For most people this is a visit to your primary care doctor, not an urgent call. MedlinePlus says to contact your health care provider if:

• You often sweat during sleep.
• You sweat a lot, or the sweating lasts a long time or cannot be explained.
• The sweating comes with a fever, weight loss, a rapid or pounding heartbeat, or shortness of breath.

MedlinePlus notes these can point to a problem such as an overactive thyroid or an infection. If a medicine looks responsible, your doctor may be able to suggest a different one.

Sweating that comes with chest pain or pressure, or sudden shortness of breath, is different. MedlinePlus lists heavy sweating among the signs of a heart attack, and says to call 911 right away for those.

This is why people search this symptom, so it deserves a straight answer.

NCI lists drenching night sweats among Hodgkin lymphoma symptoms. The full list is:

• Painless swollen lymph nodes (small glands of the immune system) in the neck, underarm or groin.
• Fever for no known reason.
• Drenching night sweats.
• Weight loss for no known reason in the past 6 months.
• Itchy skin, especially after bathing or drinking alcohol.
• Feeling very tired.

Two things stand out. The nodes are painless, which is the opposite of the tender glands you get with a sore throat. And NCI frames these as symptoms that do not go away.

Night sweats on their own, for two weeks, in someone going through menopause, is a very different picture from sweats plus a growing painless lump plus months of weight loss.

If you are having treatment, the priority changes, because a fever may mean an infection your body cannot contain.

CDC lists a fever of 100.4 F (38 C) or higher as a sign of infection, along with chills, cough or sore throat, diarrhoea, mouth sores, and redness where a line enters the body. It says to call your health care team if you have signs of an infection, because these can be life threatening and need urgent medical attention.

It also advises talking to your doctor or nurse before taking anything for a fever, since those medicines can hide a more serious problem. Use the 24-hour number your team gave you.

Sweats are hard to describe from memory, and easy to record.

Keep a note by the bed. Mark the nights it happened, whether you changed clothes or bedding, the room temperature, what you drank that evening, and your temperature if you have a thermometer. Add any new medicine.

Bring that page and your medicine list. Symptoms of Cancer explains how patterns like this get weighed.

• Call your care team now, and go to an emergency department if you cannot reach them, if you are having cancer treatment and your temperature reaches 100.4 F (38 C) or higher, or chills, a new cough, a sore throat, or redness where a line enters your body come with the sweats. NCI treats these as signs of infection that can be life threatening and need urgent medical attention. Use the 24-hour number your team gave you, and do not sit on it overnight.
• Call 911 if sweating comes with chest pain or pressure, or with sudden shortness of breath. MedlinePlus lists heavy sweating among the signs of a heart attack, which is a medical emergency.
• Call your doctor within a day or two if you are not on treatment and you often wake up sweating in a cool room, or the sweats arrive with a fever, a fast or pounding heartbeat, or weight you did not set out to lose. MedlinePlus lists these as reasons to contact your provider.

• NHS — Night sweats (definition and common causes)
• MedlinePlus — Sweating
• MedlinePlus — Heart attack
• National Cancer Institute — Adult Hodgkin Lymphoma Treatment (PDQ)
• National Cancer Institute — Infection and Neutropenia during Cancer Treatment