Fever and Night Sweats

Reviewed by: HU Medical Review Board | Last Reviewed: January 2018. | Last updated: April 2023

Fever is an increase in your body's temperature in response to disease or infection.1 Fever is a common symptom of moderate or severe Crohn's disease and of ulcerative colitis, the 2 main forms of inflammatory bowel disease (IBD).2,3 The fever probably develops as part of the inflammatory process.4 Fever also can be a side effect of several medications that treat IBD. In particular, it is a side effect of sulfasalazine, azathioprine, 6-mercaptopurine, and infliximab.2,4 Fever may be a sign of some complications of IBD. It can indicate that you have an abscess. It also can be a sign of toxic megacolon.

Night sweats are another symptom of changes in your body temperature. Normally, your body is most comfortable when the surrounding air is within a certain temperature range (thermoneutral zone).5 Inflammation may move this range upward. Therefore, instead of being comfortable when the air around you is 72°F, you suddenly feel cold. You get the chills and start to shiver, which raises your body's core temperature. When the inflammatory signals settle down, the thermoneutral zone decreases too. Suddenly, your body is too warm! In response, you begin to sweat to lower your body temperature.

If you have woken up drenched in sweat and needing to change your pajamas, you know what night sweats are. There is very little research about night sweats.5 Yet many people with IBD report this symptom.6 One theory is that the level of inflammatory signals fluctuates throughout a 24-hour period.5 This could explain why night sweats occur. However, there is no science to prove this. Another theory is that certain people are more aware of night sweats than others.5

People with IBD often have trouble sleeping. If you are waking up more frequently at night for other reasons, you may be more likely to notice sweating.

What other conditions can cause fever and night sweats?

Fever is a symptom of many conditions, including infections, malignancies, and autoimmune disorders.7 The cause of most fevers can be readily diagnosed and treated. Often, fevers get better on their own.7

Night sweats are also non-specific. People report night sweats related to cancer, infection, and hormone changes.8 They can be related to some medications, changes in blood sugar levels, pregnancy, and some mental health problems.

How common are fever and night sweats with Crohn's and UC?

A year-long survey of 704 people with inflammatory bowel disease showed that 24% of people with Crohn’s disease and 15% of people with ulcerative colitis had fever or night sweats in any 3-month period.6

Unsurprisingly, fever or night sweats were most common among people whose IBD was active throughout the year. More than 38% of people in this group had fever or night sweats. For people who cycled between periods of activity and recovery during the year, 18.6% had fever or night sweats. Interestingly, 6.1% of people with inactive disease during the year had fever or night sweats.6

How is fever evaluated?

Normal body temperature is about 98.6°F, but it fluctuates throughout the day.9 It is usually highest in the evening and during a menstrual period.1 Your body temperature may be warmer after exercise or eating, due to high heat or humidity, or when you are emotional.1

In adults, a fever is a body temperature of 100.4°F or higher.9

A child’s body temperature can be measured in the rectum, mouth, or armpit. Temperatures that indicate fever are:1

  • Measured in the rectum: ≥100.4°F
  • Measured in the mouth: ≥99.5°F
  • Measured under the arm: ≥99°F

Fever could be a sign that your IBD is flaring up.10 It may be necessary to see your health care provider for evaluation and change in medication.10

How are night sweats evaluated?

Your health care provider may do blood tests to check for an increase in inflammation. Increased inflammation could be a sign of a IBD flare, but can also indicate other conditions that cause night sweats.8

It is possible that your provider will order additional tests to rule out some of the common causes of night sweats, such as tuberculosis or HIV infection. Based on your history and other symptoms, your provider may choose to do additional tests.

How is fever treated?

General advice for a fever is to drink plenty of fluids. Do not bundle up with extra layers of clothing or bedding. This can cause your temperature to rise higher. Set the room to a comfortable temperature.1

Acetaminophen (Tylenol) may be a better option than ibuprofen (Motrin, Advil) for treating a fever.10 There is concern that taking ibuprofen (a non-steroidal anti-inflammatory drug or NSAID) could worsen a IBD flare. Ask your health care provider what type of over-the-counter medications you should take for a fever.

Fever plus bloody diarrhea, pain, abdominal swelling, rapid heart beat, dehydration, or low urine output could be serious. These are symptoms of toxic megacolon, a rare but life-threatening complication of Crohn’s disease and ulcerative colitis. If you have these symptoms, seek medical care right away.

How can I manage night sweats from Crohn's or UC?

Waking up because of night sweats can increase your fatigue. Try to get cleaned up and comfortable without turning on the lights or getting out of bed. Tips to help you get more rest include:11

  • Wear light weight pajamas and use light covers.
  • Keep the bedroom cool or use a fan.
  • Sleep on 1 to 2 towels. You can just discard the towel, avoiding the need to change your sheets.
  • Keep an extra set of pajamas in arms reach of your bed.

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