Fevers
Infection is the most common cause of fevers in people with cancer. In patients with low white blood cells (neutropenia), fever may often be the first and sometimes only sign of infection.
What is a fever?
When your temperature is higher than normal for you, you are thought to have a fever. Normally, body temperature is between 95.5℉ to 99.9℉ (35.3℃ to 37.7℃). Your body temperature can also vary depending on your age, the time of day, and how and where it’s measured. For people with cancer, a fever is defined as a temperature of 100.4℉ (38℃) or higher for at least one hour.
What causes a fever?
Fevers can be caused by:
- Infection
- Inflammation
- Reactions to medicines or cancer treatments
- Tumors
- A blood clot in the lungs (pulmonary embolism or PE)
In people with cancer, infection is the most common cause of fevers. People with cancer have a higher risk of infection because many cancer treatments can lower your white blood cell counts (called neutropenia). White blood cells fight infection.
What are neutropenic fevers?
When a person has fever and a low white blood cell count, it's called neutropenic fever or febrile neutropenia (FN). If you are neutropenic, it means you don't have enough neutrophils (or white blood cells) to fight off infection.
When you’re neutropenic, you might not have all the common symptoms of an infection. You might not have chills, sweats, or a cough. Some people with severe neutropenia might not have any signs of infection at all or might even have a lower-than-normal body temperature.
Learn more about neutropenia and low white blood cell counts.
Checking your temperature
Here are a few things to know about taking your temperature:
- Use a thermometer that goes in your mouth (oral). They are usually more accurate than temperatures taken from the armpit, ear, or forehead.
- Always clean your thermometer before and after use. Wash it with warm water and soap, or a cotton ball with isopropyl or rubbing alcohol.
- If you don’t have a thermometer, ask your cancer care team for one or where to get one. They might have one you can take home.
- Never place a thermometer in your rectum if you’re neutropenic.
If you have neutropenic fevers
When you’re neutropenic, a fever might be the only sign of infection. Infections can become life-threatening very quickly in people who have neutropenia.
Ask your cancer care team what temperature they consider to be a fever. it might be different depending on your situation, but 100.4℉ (38℃) is often used.
Ask your cancer care team if it’s okay to take any over-the-counter medicines (such as Tylenol) for fever. They might want you to avoid treating any fevers and suggest not taking anything.
Talk to your doctor or cancer care team
If you have signs or symptoms of an infection such as:
- Chills or sweats
- Cold, clammy, or pale skin
- Cough or trouble breathing
- New or worse confusion
- Having pain when you pee
- Not having to pee or peeing only very little amounts that are dark orange or brown
- Written by
- References
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 editors and translators with extensive experience in medical writing.
National Comprehensive Cancer Network (NCCN). Anemia and neutropenia: Low red and white blood cell counts. NCCN Guidelines for Patients. Updated 2021. Accessed November 21, 2023. https://www.nccn.org/patients/guidelines/content/PDF/anemia-patient-guideline.pdf
National Comprehensive Cancer Network (NCCN). Prevention and treatment of cancer-related infections. Version 1.2023. NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines). Updated June 2023. Accessed November 21, 2023. https://www.nccn.org/professionals/physician_gls/pdf/infections.pdf
Neviere R. Sepsis syndromes in adults: Epidemiology, definitions, clinical presentation, diagnosis, and prognosis. UpToDate. UpToDate Inc; 2023. Updated September 2023. Accessed November 22, 2023. https://www.uptodate.com/contents/sepsis-syndromes-in-adults-epidemiology-definitions-clinical-presentation-diagnosis-and-prognosis
Taplitz RA, Kennedy EB, Bow EJ, et al. Antimicrobial prophylaxis for adult patients with cancer-related immunosuppression: ASCO and IDSA clinical practice guideline update. J Clin Oncol. 2018 Oct 20;36(30):3043-3054. doi: 10.1200/JCO.18.00374.
Wingard JR. Overview of neutropenic fever syndromes. UpToDate. UpToDate Inc; 2023. Updated May 2022. Accessed November 21, 2023. https://www.uptodate.com/contents/overview-of-neutropenic-fever-syndromes
Wingard JR. Prophylaxis of infection during chemotherapy-induced neutropenia in high-risk adults. UpToDate. UpToDate Inc; 2023. Updated July 2022. Accessed November 21, 2023. https://www.uptodate.com/contents/prophylaxis-of-infection-during-chemotherapy-induced-neutropenia-in-high-risk-adults?
Last Revised: February 13, 2024
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