Radiation Therapy and Fever: What You Should Know

Yes, fever can occur during radiation therapy, and it’s important to take it seriously. Fever (100.4°F or 38°C and higher) during radiation treatment should prompt contacting your care team, because it can signal an infection that needs timely evaluation. ^[1] Fever with shaking chills or flu-like symptoms is specifically flagged by cancer centers as a reason to call your radiation oncology team right away. ^[1]

Why Fever Happens

• Possible infection during treatment: Even though radiation itself doesn’t “make you infectious,” people receiving cancer therapy can be more vulnerable to infections, and fever may be the first sign. ^[1] Fever together with chills or flu-like symptoms should be assessed to rule out pneumonia or other respiratory infections. ^[2]
• Treatment-related inflammation: Radiation can inflame the treated area and surrounding tissues, which may contribute to feeling unwell; however, providers still advise checking for infection whenever fever appears during therapy. ^[1]
• Blood count changes: Radiation (especially to large fields or in combination with other treatments) can lower blood cell counts, which raises infection risk and may necessitate pausing treatment until counts recover. ^[3]

When to Seek Medical Attention

• Call your radiation clinic promptly for any fever ≥100.4°F (38°C). This threshold is consistently used as the trigger to contact your provider. ^[1]
• Report accompanying symptoms: Shaking chills, cough, sore throat, body aches, or worsening discomfort in the treated area should be communicated. ^{[1] [4]}
• Urgency matters: Early evaluation helps identify infections and start appropriate treatment, which can prevent complications. ^[1]

Practical Coping Steps

• Monitor temperature regularly: If you feel warm, flushed, or chilled, check your temperature promptly and keep a simple log to share with your team. ^[1]
• Hydrate and rest: Fluids and rest can support recovery while you await guidance from your care team. Still, do not delay calling for fever. ^[1]
• Skin care in the treated area: Gentle cleansing, moisturizing as instructed, and avoiding irritation can reduce local inflammation; report any painful, peeling, blistering, or weepy skin. ^[4]
• Infection precautions: Good hand hygiene, oral care, and avoiding sick contacts can help; watch for redness or swelling at sites like the mouth, skin folds, catheter areas, or biopsy sites and report concerns. ^[2]
• Medication guidance: Use fever reducers (like acetaminophen) only after speaking with your care team, because they can mask symptoms that are important for diagnosis. ^[1]

What Your Care Team Might Do

• Clinical evaluation: A physical exam and symptom review will look for common infection sources (lungs, mouth, skin, urinary tract). ^[2]
• Testing: Blood tests, including complete blood counts, may be checked and imaging or cultures ordered if needed. If counts are low, radiation may be paused until they improve. ^[3]
• Treatment: If an infection is suspected or confirmed, antibiotics and supportive care are typically started promptly. ^[1]

Key Takeaways

• Fever during radiation therapy (≥100.4°F/38°C) warrants a prompt call to your radiation oncology team. ^[1]
• Because infection is a common and important cause of fever during cancer treatment, timely evaluation is essential. ^{[1] [2]}
• Practical steps temperature monitoring, hydration, careful skin/oral care, and early reporting of symptoms help you cope safely. ^{[1] [4]}

---

Quick Reference: Fever During Radiation Therapy

What to watch	Why it matters	What to do
Fever ≥100.4°F (38°C)	May indicate infection needing prompt treatment	Call your radiation oncologist or nurse the same day. [1]
Shaking chills or flu-like symptoms	Can be signs of respiratory infection	Report immediately; may need evaluation for pneumonia. [2] [1]
Painful, peeling, blistering, or weepy skin	Potential severe skin reaction	Contact your care team for advice and assessment. [4]
Worsening cough, sore throat, chest discomfort	Possible respiratory source	Seek evaluation and follow instructions from your clinic. [2]
Low energy, poor intake, dehydration	Can worsen recovery and mask illness	Hydrate, rest, and update your team, especially if fever persists. [1]

Staying alert to fever and communicating early with your treatment team helps keep your therapy on track and protects your health. ^{[1] [3]}