The short answer
NCI says to call the health care team for signs of infection during treatment. Confusion, very fast breathing, mottled skin or other signs of sepsis mean calling 911. Those are two different tiers and it matters which one.
A fever of 100.4°F (38°C) or higher during treatment is a sign of infection. CDC says to call your doctor right away, even in the middle of the night. If you cannot reach your team, go to the emergency room or call 911.
Confusion, very fast breathing, shortness of breath, a high heart rate or weak pulse, mottled skin, or extreme pain are signs of sepsis. Call 911.
NCI says to talk to a doctor or nurse before taking aspirin, acetaminophen or ibuprofen for a fever, because they can mask a more serious problem.
MedlinePlus says a weakened immune system and lines or tubes into the body raise the risk of sepsis. Say you are on chemotherapy, and name any line or catheter, at the desk.
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The whole article, with every detail and caution.
This page is for people having cancer treatment, and their caregivers, who want to know the signs of infection and sepsis (the body's extreme, life-threatening response to an infection).
Call the oncology team for any of these
NCI's instruction is short. Call your health care team if you have signs of an infection. Infections during cancer treatment can be life threatening and require urgent medical attention.
This is the list NCI gives:
- A fever of 100.4°F (38°C) or higher. CDC says to call your doctor immediately at that number during chemotherapy. If your team has given you a lower number, use theirs.
- Chills.
- Cough or sore throat.
- Diarrhea.
- Ear pain, headache or sinus pain, or a stiff or sore neck.
- Skin rash.
- Sores or white coating in the mouth or on the tongue.
- Swelling or redness, especially where a catheter enters the body.
- Urine that is bloody or cloudy, or pain when urinating.
Every one of those is a phone call to oncology, made when you notice it, not a portal message and not a wait until morning. CDC calls a fever during chemotherapy an emergency. If you cannot reach your team, go to the emergency room or call 911.
That holds while the person is otherwise stable. If any of the signs in the emergency list further down are there too — fast breathing, confusion, mottled or blue-tinged skin, a weak fast pulse, severe pain, or someone who simply looks to be going downhill — that is 911, not a phone call to the clinic.
Use your own team's instructions where they are more cautious.
The number moves by a tenth of a degree
Use 100.4°F (38°C) or higher, the threshold CDC and MedlinePlus give. Sources word this threshold differently, so you may have seen other figures.
If your own team gave you a lower number, use theirs. If you are not sure, call. No oncology service minds being called about a fever.
The signs that go past a phone call
Some signs are past a call to the clinic. If you see any of these, call 911. Do not drive yourself. CDC lists these as the signs of sepsis:
- Confusion or disorientation.
- Shortness of breath.
- A high heart rate or a weak pulse.
- Fever, shivering, or feeling very cold.
- Extreme pain or discomfort.
- Clammy or sweaty skin.
MedlinePlus adds that a change in mental status and very fast breathing may be the earliest signs of sepsis. It also lists mottled skin and a skin rash. If you think something is seriously wrong, call 911 even if not every sign is there.
CDC says that without fast treatment, sepsis can quickly lead to tissue damage, organ failure and death.
Do not drive yourself. Call 911 for an ambulance. Bring your medicines with you, and say at the door that you are having cancer treatment.
Why the fever medicine can wait
The temptation is to take something, watch for an hour, and call only if it does not settle.
NCI's wording rules that out. Talk with your doctor or nurse before taking medicine for a fever, even aspirin, acetaminophen or ibuprofen. Its reason is not that the medicines are dangerous. It is that they can lower a fever but may also mask or hide signs of a more serious problem.
Making the call first does not stop you taking anything afterwards. It just stops the one thing that hides the picture.
What to say at the desk
Triage (the first check at the emergency desk) sorts people by how sick they look. Someone with low counts can look well and be in serious trouble, so the history has to do the work.
MedlinePlus names two things that raise the chance of sepsis and that apply to a lot of people in treatment: a weakened immune system, and lines or tubes into the body. NCI separately lists swelling or redness where a catheter enters the body as a sign of infection to report.
So say both out loud:
- "I am having chemotherapy." Name the drug and the date of the last dose if you can.
- "I have a port" or "I have a central line" or "I have a urinary catheter."
- The temperature, and the time you took it.
- Anything from NCI's infection list above.
Carrying a card or a phone note with the diagnosis, the regimen, the last treatment date and the oncology after-hours number makes this much easier when you feel awful.
When in the cycle the risk peaks
NCI explains why this is a treatment problem rather than a general one. Some cancers and treatments such as chemotherapy lower the number of white blood cells, the cells that fight infection.
More usefully, it says the risk is not flat. During chemotherapy there will be times in the cycle when the number of neutrophils is particularly low, and the risk of infection is higher then. Blood tests are used to check for neutropenia.
That is worth asking about by name, because it turns a vague worry into specific days.
What hospital treatment involves
MedlinePlus says people with sepsis are usually treated in the hospital, often in an intensive care unit. Treatment includes:
- Antibiotics given into a vein
- Oxygen to help with breathing
- Fluids given into a vein, and sometimes medicines to raise blood pressure
Knowing that in advance takes some of the fright out of the words "we are admitting you."
Related pages
Preparing for an Emergency Department Visit With Cancer, and What Counts as a Fever During Chemotherapy?.
Sources
Common questions
What temperature counts?
A fever of 100.4°F (38°C) or higher is the threshold CDC and MedlinePlus give. If your own team gave you a lower number, use theirs. If you are not sure, call.
Is a fever a call or a 911 trip?
CDC says a fever of 100.4°F (38°C) or higher during chemotherapy is an emergency: call your doctor immediately, at any hour. If you cannot reach your team, go to the emergency room or call 911. NCI's instruction for signs of infection is to call your health care team, and it says infections during cancer treatment can be life threatening and require urgent medical attention. Call 911 for signs of sepsis: confusion, shortness of breath or very fast breathing, a high heart rate or weak pulse, shivering or feeling very cold, extreme pain, clammy skin, or mottled skin.
Can I take something to bring the fever down and see what happens?
NCI says to talk with your doctor or nurse before taking medicine for a fever, even aspirin, acetaminophen or ibuprofen. Its reason is specific: those medicines can lower a fever but may also mask or hide signs of a more serious problem. Making the call first does not stop you taking anything later.
What should I say at the emergency department desk?
Say you are having chemotherapy, and say if you have a line, port or catheter. MedlinePlus says a weakened immune system and lines into the body raise the risk of sepsis. Give the temperature and the time you took it, say when your last treatment was, and bring your medicines or a list.
How fast does sepsis move?
CDC says that without fast treatment sepsis can quickly lead to tissue damage, organ failure and death. That speed is the reason the response is a phone call rather than a wait.
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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: 2026-08-11 what this meansLast updated: 2026-09-29Next planned review: 2027-01-22
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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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