Fever During Cancer Treatment: What’s Normal and How It’s Managed

Fever can occur during cancer treatment, and it has several possible causes; importantly, a fever during chemotherapy can be a medical emergency because it may be the only sign of a serious infection. ^[1] A temperature of 38.0–38.3°C (100.4–100.5°F) or higher should generally prompt you to call your care team right away, as advised for people receiving chemotherapy. ^{[2] [3]}

Why fever happens

• Infection risk from low white blood cells: Many chemotherapy drugs temporarily lower white blood cells (neutropenia), which reduces your ability to fight infections; fever can be the only early clue. ^[3] Infection during chemotherapy can become life‑threatening if not treated quickly, so fever needs immediate attention. ^[1]
• Tumor- or treatment-related inflammation: Some cancers and treatments can cause inflammatory fevers even without infection, which is sometimes called “neoplastic fever.” ^[4]
• Immune therapies and targeted drugs: Immunotherapies and certain targeted agents can trigger cytokine-related fevers; these require careful assessment to rule out infection and to grade severity. ^{[5] [6]}

When fever is an emergency

• If you are on chemotherapy and your temperature is 38.0°C (100.4°F) or higher, call your oncology team immediately or go to urgent care/emergency and tell them you are on chemotherapy. ^{[2] [1]}
• Fever may be your only symptom of infection; do not wait for other signs like cough or burning with urination. ^[7]
• In the emergency department, rapid evaluation and treatment are needed; time matters. ^[8]

What clinicians do to manage fever

• Treat as neutropenic fever until proven otherwise: Anyone with recent anti‑cancer therapy and fever is managed as if neutropenic until lab results show otherwise. ^[8]
• Start antibiotics promptly: Broad‑spectrum intravenous antibiotics are started quickly ideally within 30–60 minutes for patients who appear unwell without waiting for test results, then tailored as data return. ^{[8] [9]}
• Labs and cultures: Blood tests (including a complete blood count for neutrophils) and cultures are taken, and a chest X‑ray is often arranged to look for infection sources. ^[9]
• Risk assessment: Tools such as the MASCC score help identify who might be safely managed as an outpatient versus who needs admission. ^[10]

Special considerations by treatment type

• Chemotherapy: Any fever is treated as a potential infection; you will usually receive urgent antibiotics and monitoring, especially if your white blood cell count is low. ^[8]
• Immunotherapy (cytokine‑related fever): If fever occurs with drugs that can cause cytokine release syndrome (CRS), clinicians grade severity and may give antipyretics, antibiotics while infection is excluded, fluids, and sometimes tocilizumab or steroids based on CRS grade. ^{[5] [6]}
• Targeted therapies (e.g., BRAF/MEK inhibitors): Some regimens have characteristic fever syndromes; management often includes holding the drug, antipyretics, and stepwise re‑challenge per protocol. ^[11]

What you can do right now

• Keep a working thermometer and check your temperature any time you feel warm, flushed, chilled, or unwell. ^[7]
• Call your oncology team promptly if your temperature is 38.0°C (100.4°F) or higher, even if you feel “okay.” ^[2]
• If you go to the ER, state clearly that you are receiving chemotherapy so you can be seen quickly. ^[1]
• Practice infection prevention every day frequent handwashing is one of the simplest, most effective steps. ^[2]

At-home comfort while awaiting care

It’s reasonable to rest, hydrate, and consider antipyretics like acetaminophen if your clinician has told you it’s safe for you; however, antipyretics can mask fever, so they should not delay urgent evaluation when you meet the temperature threshold. Fever during active chemotherapy still needs immediate medical attention. ^{[2] [1]}

Key thresholds and actions

• Temperature ≥ 38.0°C (100.4°F) during chemotherapy: call immediately; this is treated as a medical emergency. ^[2]
• Feeling unwell with chills, rigors, or new symptoms during treatment: check your temperature and contact your team. ^[7]
• Signs of low blood counts such as fever with chills: seek prompt medical care. ^[3]

Why speed matters

Early antibiotics in suspected neutropenic fever lower the chance of severe complications and improve outcomes; protocols emphasize giving the first dose quickly, often within 30–60 minutes for compromised patients. ^[8] [PM13]

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If you’d like, I can help you create a personalized “fever plan” with who to call, thresholds, and what to bring if you need to visit urgent care.