Fever and when to get help during cancer treatment

Clear lists to help you decide: a fever of 38.0 °C (100.4 °F) during chemotherapy is an emergency. Plus when to call 9-1-1, when to call your cancer centre's 24-hour line, and immunotherapy side effects to report.

6 min read · last reviewed September 30, 2026

During cancer treatment, it can be hard to know which problems can wait and which need help now. This page helps you and your family decide. Print it, stick it on the fridge, and keep your cancer centre's 24-hour phone number beside it.

Your own team may give you slightly different instructions. Always follow the advice from your own cancer centre.

Fever during chemotherapy is an emergency

Chemotherapy can lower the number of white blood cells that fight infection. This is called neutropenia. White blood cells are often lowest about 1 to 2 weeks after a chemo treatment, but they can be low at other times too. When your white blood cells are low, an infection can become serious very quickly, even if you feel fairly well.

If you are having chemotherapy and your temperature is 38.0 °C (100.4 °F) or higher:

• Call your cancer centre's 24-hour line right away, or go to the nearest emergency department. Don't wait until morning.
• Don't take medicine to lower the fever (such as acetaminophen or ibuprofen) before you call, unless your team has told you to. These medicines can hide a fever and delay treatment.
• Tell the staff you are having chemotherapy, and when your last treatment was. If your centre gave you a fever or chemo alert card, show it.
• If you feel very unwell, for example confused, very drowsy, dizzy or short of breath, call 9-1-1.

Also call right away if you have chills or shaking, even without a fever. People on some medicines, such as steroids, may have an infection without a high temperature.

Something you can do today: Keep a digital thermometer at home. Check your temperature whenever you feel hot, cold, shivery or unwell.

Call 9-1-1 or your local emergency number

Call right away if you or the person you care for has:

• Chest pain or pressure.
• Severe trouble breathing, or sudden shortness of breath. People with cancer have a higher chance of blood clots, which can travel to the lungs.
• New confusion, or is very hard to wake up.
• A seizure (fit).
• Heavy bleeding that won't stop, or vomiting or coughing up blood.
• Signs of a stroke: face drooping, arm weakness or trouble speaking.
• Fainting, or collapsing.

Get help right away: signs of spinal cord compression

Sometimes cancer that has spread to the bones of the spine can press on the spinal cord. This is called spinal cord compression. It is an emergency, because fast treatment can help prevent lasting damage. Signs include:

• New back or neck pain, especially if it gets worse when lying down, or feels like a band around your chest or tummy.
• Weakness in your legs, or legs that feel unsteady or give way.
• Numbness or tingling in your legs, buttocks or around your bottom.
• Loss of control of your bladder or bowels, or not being able to pass urine.

If you have leg weakness, numbness, or problems controlling your bladder or bowels, call 9-1-1 or go to emergency now. If you have new back pain alone, call your cancer centre's 24-hour line right away. Don't wait for more symptoms to develop.

Call your cancer centre's 24-hour line now

These problems need advice the same day, and often right away. Don't wait for your next appointment:

• Fever of 38.0 °C (100.4 °F) or higher, or chills or shaking.
• Vomiting that won't stop, or you can't keep fluids or medicines down.
• Diarrhea that is severe, or happens several times a day.
• New or worsening pain, or pain that your medicines don't control.
• Signs of infection: cough, sore throat, burning when you pee, or redness, swelling or pus around a wound or a line (such as a port or PICC line).
• Mouth sores that stop you eating or drinking.
• Unusual bleeding or bruising, nosebleeds, or blood in your pee or poop.
• Pain, swelling, warmth or redness in one leg or arm (a possible blood clot).
• Feeling dizzy, very weak, or passing much less pee than usual.
• New numbness, tingling or trouble using your hands or feet.

When in doubt, call. Cancer teams would much rather hear from you early. No one will think you are a bother.

Immunotherapy: side effects to report

Immunotherapy (such as checkpoint inhibitors) helps your immune system attack cancer. Sometimes the immune system also attacks healthy parts of the body. Most of these side effects can be treated well if they are caught early. They can appear during treatment, or weeks to months after it ends.

Call your team if you notice:

• Diarrhea, belly pain, or blood or mucus in your poop.
• A new cough or shortness of breath.
• A rash, itching or blisters.
• Yellow skin or eyes, dark pee, or pain on the right side of your belly.
• Headaches, extreme tiredness, dizziness, or feeling very thirsty or peeing a lot. These can be signs of a problem with hormone glands.
• Muscle weakness, joint pain, a fast heartbeat, or changes in your vision.

Tell any doctor, nurse or emergency department that you have had immunotherapy, even if it was months ago. Carry your immunotherapy alert card if you have one.

Before you need it

• Save your cancer centre's 24-hour number in your phone, and share it with family.
• Keep a list of your cancer treatments, your last treatment date and your medicines.
• Pack a small bag with your list, your health card and a phone charger, in case you need to go to hospital.
• Ask your team for written instructions about fever and other urgent problems.

Questions to ask your care team

• What number do I call day or night? What if no one answers?
• At what temperature should I call you? Should I go to emergency or call first?
• When are my white blood cells likely to be lowest?
• Can I take anything for pain or fever at home?
• Which side effects of my treatment should I report right away?
• Do I need an alert card to show at the emergency department?

This article is general information, not medical advice. Talk with your health care team about your own situation. In an emergency, call 9-1-1 or your local emergency number.

In an emergency, call 9-1-1 or your local emergency number.

General information, not medical advice. It does not replace your own care team. If you think you or someone else is having a medical emergency, call 9-1-1 or your local emergency number. If you are in crisis or thinking about suicide, call or text 9-8-8 (Canada and the US).

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