The short answer
A fever of 100.4 F (38 C) or higher during chemotherapy is a medical emergency, so call your care team immediately, at any hour, or go to an emergency department. Shaking chills, confusion, trouble breathing, a stiff neck, a new rash, feeling very unwell, or redness at a port or PICC also need care right away. Know your team's number and after-hours line.
Fever during chemotherapy can be more serious than fever at other times because some treatments lower infection-fighting white blood cells. The most important plan is the one your oncology team gave you.
The right next step depends on treatment type, timing, symptoms, lab results, and the urgent plan from the oncology team.
Having concrete details ready makes the urgent call faster and more useful.
Choose how you want to read this
The whole article, with every detail and caution.
This page is for people having chemotherapy, and their caregivers, who want to know what to do about a fever. It starts with when to go in, then explains the numbers, what to do ahead of time, and what happens at the hospital.
Go to the emergency department right away if you have any of these
Do not wait for a callback if you have a fever and any of these. If you cannot reach your team quickly, go. For severe symptoms, call 911.
- Your temperature reaches your team's threshold, or 100.4 F (38 C) if you were not given one.
- Shaking chills, even with a normal temperature.
- Confusion or disorientation, or a new stiff neck.
- Shortness of breath or trouble breathing.
- A fast heartbeat or weak pulse, clammy or sweaty skin, or extreme pain. CDC lists these, along with confusion, fever or shivering, and shortness of breath, as signs of sepsis. Sepsis is a life-threatening emergency.
- Redness, soreness, swelling or discharge around a port, PICC line or wound.
- Any fever in the days when your blood count is likely at its lowest. CDC says counts usually reach their lowest point 7 to 12 days after each chemotherapy dose. Ask your team for your own dates.
Do not drive yourself. Tell the person checking you in that you are having chemotherapy. MedlinePlus advises saying so right away, rather than sitting in the waiting room, where you may be exposed to infections.
Call your team right away, at any hour, for these too
You do not need a fever for these to matter. CDC says to call your doctor right away if you have:
- Chills or sweats.
- A new cough or a change in your cough.
- A sore throat or a new mouth sore.
- Nasal congestion.
- Burning or pain when you pass urine, or unusual vaginal discharge or irritation.
- Diarrhea, vomiting, or belly or rectal pain.
- A new rash, or redness, soreness or swelling anywhere.
- New pain.
When your white blood cell count is low, infection can be dangerous and signs can be easy to miss. Take small changes seriously.
What to have ready before you call
- Your temperature and the time you took it.
- The name of your chemotherapy and the date of your last dose.
- Your most recent blood count, if you have it.
- Whether you have a port or PICC line.
- Any medicine allergies.
- Your other symptoms, from the lists above.
- Who is driving you, since you may be admitted.
Which number to use
CDC and MedlinePlus say to call your doctor immediately for a temperature of 100.4 F (38 C) or higher. NCI describes a fever as 100.5 F (38 C) or higher. The numbers are close, so do not wait for the higher one. Use 100.4 F.
If your team gave you a lower number, use theirs. If nobody gave you a number, use 100.4 F and call. Do not wait an hour and check again.
Do not take acetaminophen, aspirin, ibuprofen or naproxen for a fever before you talk with your doctor or nurse. NCI says these medicines can lower a fever but may hide a more serious problem.
Get ready before a fever happens
CDC suggests these steps:
- Keep a thermometer where you can find it, and take your temperature if you feel unwell.
- Keep your doctor's phone number, including the after-hours line, with you.
- Ask when your white blood cell count is likely to be lowest.
What neutropenia means
Neutrophils are white blood cells that fight infection. Some chemotherapy lowers their number for a time. A low number is called neutropenia. MedlinePlus says fewer than 1,000 neutrophils per microliter of blood is low, and fewer than 500 is severe.
Why it is an emergency
CDC says a fever may be the only sign of an infection, and an infection during chemotherapy can be life threatening. MedlinePlus calls an infection during cancer treatment an emergency. That is why you should not wait and see.
What happens when you arrive
The hospital team will check you and decide which tests and treatment you need. What they do depends on your health, your treatment and your test results. Ask them to explain each step.
After the emergency visit
The team decides whether you stay in the hospital or follow a plan at home. If you go home, follow the instructions exactly. Call your care team right away if the fever does not go away or you feel worse. For emergencies call 911 or go to the ER.
Related pages
Low White Blood Cells During Chemotherapy, Neutropenia During Chemotherapy, Neutropenic Fever During Cancer Treatment, and Chemotherapy.
Sources
Opened and checked on 2026-10-02:
Common questions
Does a fever during chemo always mean treatment must change?
No. It depends on severity, timing, treatment type, test results, and the full clinical picture. The care team decides whether the plan needs monitoring, supportive care, more testing, or a treatment change.
What should I have ready when I contact the care team?
Have the treatment name, most recent treatment date, symptom timing, related symptoms, medicines already taken, and any recent lab or scan information if available.
Can I manage this on my own at home?
Use the plan your oncology team gave you. Cancer treatment can change the risk level of common symptoms, so ask before using new medicines or waiting through symptoms that are new, severe, or worsening.
Questions to ask your doctor
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Your next step
Write down timing, severity, triggers, and what helps.
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
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Sources last checked: 2026-07-20 what this meansLast updated: 2026-09-29Next planned review: 2027-01-21
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High-risk topic — talk to your care team. This topic can involve urgent, individual medical decisions. This page is general education only: it cannot tell you whether your situation is an emergency or what you personally should do. Follow your oncology team's instructions and contact them for individual guidance.
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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