Fever is a body temperature of 100.5° F or higher (when taken by mouth) that most often goes up and down over the course of a day. Fever is usually caused by an infection. Other causes of fever include inflammatory illness, drug reactions, or tumor growth. Sometimes, the cause may not be known. In an infection, the fever is a result of the body “heating up” to try to fight invading germs. Fever is an important natural defense against germs.

People getting chemo are more likely to have infections because they have lower numbers of the white blood cells needed to fight them. You can buy an easy-to-use oral thermometer (one made to take your temperature by mouth) at any drugstore so you can check to see if you have a fever.

What to look for

  • Increased skin temperature
  • Feeling warm
  • Feeling tired
  • Headache
  • Feeling cold
  • Shaking chills
  • Body aches
  • Skin rashes
  • Any new area of redness or swelling
  • Pus or yellowish discharge from an injury or other location
  • New cough or shortness of breath
  • New belly pain
  • Burning or pain when urinating (peeing)
  • Sore throat
  • The patient is confused, becomes forgetful, isn’t making sense, or can’t tell you where they are.

What the patient can do

  • If you start feeling warm or cold, check your temperature by mouth every 2 to 3 hours. If you can’t hold a thermometer in your mouth, hold it under your arm, in your armpit.
  • Keep a record of temperature readings.
  • Drink a lot of liquids (such as water, fruit juices, ice pops, and soups).
  • Get enough rest.
  • Use a cold compress on your forehead if you feel hot.
  • Take acetaminophen (Tylenol®) or other medicines for fever only if you’ve been told to do so.

What caregivers can do

  • Watch for shaking chills, and check the patient’s temperature after the shaking stops.
  • Check the patient’s temperature by placing the thermometer in the mouth or in their armpit. (Do not take the temperature rectally unless you’ve been told it’s OK.)
  • Offer extra fluids and snacks.
  • Help the patient take their medicines on schedule.
  • To help prevent fevers and infections, encourage visitors who have a fever, diarrhea, a cough, or the flu to visit the patient only by phone until they are well again.

Call the cancer team if the patient:

  • Is confused, doesn’t know where they are, becomes forgetful, or isn’t making sense
  • Has a temperature of 100.5° F or higher when taken by mouth
  • Has 2 or more of the symptoms listed in the “What to look for” section
  • Has a fever that lasts more than 24 hours (or goes away and comes back over 24 hours)
  • Has shaking chills
  • Cannot take in fluids

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Fauci AS, Braunwald E, Kasper DL, et al (Eds). Harrison’s Principles of Internal Medicine, 17th ed. New York: McGraw-Hill Medical, 2008.

Camp-Sorrell D, Hawkins RA. Clinical Manual for the Oncology Advanced Practice Nurse, Second Ed. Pittsburgh: Oncology Nursing Society, 2006.

Cope DG, Reb AM. An Evidence-Based Approach to the Treatment and Care of the Older Adult with Cancer. Pittsburgh: Oncology Nursing Society, 2006.

Houts PS, Bucher JA. Caregiving, Revised ed. Atlanta: American Cancer Society, 2003.

Kaplan M. Understanding and Managing Oncologic Emergencies: A Resource for Nurses. Pittsburgh: Oncology Nursing Society, 2006.

Kuebler KK, Berry PH, Heidrich DE. End-of-Life Care: Clinical Practice Guidelines. Philadelphia: W.B. Saunders Co. 2002.

National Comprehensive Cancer Network. Palliative Care. Version 1.2015. Accessed at www.nccn.org/professionals/physician_gls/pdf/palliative.pdf on March 19, 2015.

National Comprehensive Cancer Network. Prevention and Treatment of Cancer-Related Infections. Version 2.2014. Accessed at www.nccn.org/professionals/physician_gls/pdf/infections.pdf on March 19, 2015.

Oncology Nursing Society. Cancer Symptoms. Accessed at www.cancersymptoms.org on April 3, 2013.

Ripamonti C, Bruera E. Gastrointestinal Symptoms in Advanced Cancer Patients. New York: Oxford University Press, 2002.

Varricchio CG. A Cancer Source Book for Nurses, 8th ed. Sudbury, MA: Jones and Bartlett, 2004.

Yarbro CH, Frogge MH, Goodman M. Cancer Symptom Management, 3rd ed. Sudbury, MA: Jones and Bartlett, 2004.

Last Medical Review: June 8, 2015 Last Revised: June 8, 2015

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