What causes fevers during Leukemia treatment and when should I go to the ER

Fevers During Leukemia Treatment: What You Need to Know

I appreciate this important question—fever management is critical during leukemia treatment. Let me explain what causes fevers and when you need emergency care.

Why Fevers Happen During Treatment

Fevers during leukemia treatment occur for several interconnected reasons:

1. Low White Blood Cell Counts (Neutropenia) During chemotherapy and other systemic therapies, your bone marrow's ability to produce healthy white blood cells is temporarily suppressed. According to the NCCN Guidelines for Patients: Acute Myeloid Leukemia, your care team monitors your absolute neutrophil count (ANC)—the number of infection-fighting white blood cells you have. When this count drops significantly, your body loses its primary defense against bacteria, viruses, and fungi. Even minor infections can develop quickly and cause fever.

2. Direct Effects of Treatment Chemotherapy and targeted therapies can damage the lining of your mouth, throat, and digestive tract, creating entry points for infection. Treatment can also affect your immune system's ability to respond normally.

3. The Leukemia Itself According to the NCCN Guidelines, leukemia cells can release substances that trigger fever as your body responds to the abnormal cells.

4. Other Infections You may be more susceptible to common infections (respiratory, urinary tract, etc.) due to your weakened immune system.

When to Go to the ER: Red Flags

GO TO THE EMERGENCY ROOM IMMEDIATELY if you have:

• Fever of 100.4°F (38°C) or higher — This is the standard threshold during cancer treatment. Don't wait; go right away.
• Fever with chills or shaking — This suggests a more serious infection
• Difficulty breathing or shortness of breath
• Chest pain or pressure
• Severe headache, especially with neck stiffness — Could indicate infection of the fluid around your brain
• Confusion or difficulty thinking clearly
• Severe abdominal pain or persistent vomiting
• Blood in urine, stool, or vomit
• Severe bleeding or bruising that appears suddenly
• Signs of severe infection: extreme weakness, dizziness, or fainting
• Any fever if you're currently receiving active chemotherapy or within 2 weeks of completing treatment

Important Context

Your care team should have given you specific fever protocols before you started treatment. Ask your oncology team NOW (before treatment starts or at your next visit):

1. What exact temperature threshold should I use to call or go to the ER? (Usually 100.4°F, but confirm yours)
2. Do you have an on-call number I should use for fever questions?
3. Should I take my temperature at home? How often?
4. Are there any signs besides fever that mean I should go to the ER?
5. What should I do if I develop a fever on a weekend or after hours?

What to Do If You Have a Fever

Before going to the ER:

• Take your temperature with a reliable thermometer
• Write down: your temperature, when it started, any other symptoms, all medications you're taking
• Call your oncology team's on-call number if available—they may want to see you at the cancer center instead of the ER
• Don't take aspirin or ibuprofen without asking your care team first (they may affect your treatment)

At the ER:

• Tell them immediately that you have leukemia and are undergoing treatment
• Mention your low white blood cell count if you know it
• Bring a list of all your medications and recent treatments

Why This Matters

Fever during leukemia treatment is taken very seriously because infections can progress rapidly when your immune system is compromised. Early evaluation and treatment can prevent serious complications. According to the NCCN Guidelines, monitoring blood counts and managing infections is a key part of supportive care during leukemia treatment.

This information is for educational purposes only. Always consult your healthcare team for personalized medical advice and decisions. Your oncology team should provide you with specific fever protocols before you start treatment—make sure you have these instructions in writing.