Low White Blood Cells in Leukemia: What It Means and What to Do

Low white blood cells especially low neutrophils (neutropenia) are common in leukemia and during its treatment, and they generally mean a higher risk of infections. When neutrophils are very low, even the usual bacteria on the skin, mouth, and gut can cause serious illness. ^[1] Adults with fewer than about 1,000 neutrophils per microliter have neutropenia, and fewer than 500 is considered severe. ^[2] Chemotherapy and some cancers themselves reduce white cells, making it harder for the body to fight infections. ^{[3] [4]}

Why Counts Go Low

• Leukemia affects the bone marrow, reducing healthy white cell production. ^[4]
• Chemotherapy targets fast‑growing cells, which includes cancer cells and healthy white cells, leading to predictable dips 7–12 days after treatment. ^[5]
• Neutropenia often has no symptoms itself and is found on blood tests; repeat testing may be needed because levels can vary. ^{[6] [7]}

How Concerned Should You Be?

It’s reasonable to be concerned, mainly because infection risk rises as counts fall. A very low white blood cell count over time means you can get infections more easily and should take precautions to avoid exposure. ^[8] When neutrophil levels are very low, common bacteria can cause serious illness, so prompt attention to fever or infection signs is crucial. ^{[9] [10]}

Warning Signs to Act On

• Fever of 100.4°F (38°C) or higher, chills/sweats, new or worsening cough, shortness of breath, sore throat, mouth ulcers, painful urination, redness or swelling around a line or wound. Seek care promptly. ^[10]
• Any fever after cancer therapy should be treated as possible neutropenic fever and needs rapid antibiotics, especially if there are signs of low blood pressure, confusion, or organ problems. ^[11]

What Your Care Team May Do

• Monitor with complete blood counts (CBC) and differential, paying special attention to neutrophils. ^[3]
• Use preventive strategies during high‑risk periods, such as antimicrobial prophylaxis in selected patients to reduce febrile neutropenia and bloodstream infections. [PM13]
• Consider white blood cell growth factors (G‑CSF) in certain regimens to shorten the duration of severe neutropenia and lower infection risk. [PM21]
• Treat febrile neutropenia quickly with empiric, broad‑spectrum antibiotics, often starting within 30–60 minutes when severe features are present, then adjust as results and clinical course evolve. ^{[11] [12] [13] [14]}

Practical Safety Tips

• Hygiene first: frequent handwashing and avoiding sick contacts reduce infection risk. ^[8]
• Food safety: choose well‑cooked foods, wash produce thoroughly, and avoid raw meats/seafood to lower exposure to germs. ^{[15] [16]}
• Skin and mouth care: gentle oral care, moisturize skin, and protect against cuts to reduce entry points for bacteria. ^{[15] [16]}
• Know your “nadir”: counts commonly dip 7–12 days after chemotherapy; take extra precautions then. ^[5]
• Call early: report fever or infection symptoms right away; waiting can allow rapid progression. ^[10]

Understanding the Numbers

Term	Typical Meaning	Why It Matters
White blood cell (WBC) count	Total infection‑fighting cells	Lower counts generally mean higher infection risk. [17]
Neutrophils (ANC)	Key WBC subtype against bacteria	ANC <1,000 = neutropenia; <500 = severe neutropenia. [2]
“Nadir”	Lowest point after chemo (often day 7–12)	Highest risk window for infections. [5]

Bottom Line

• Low white blood cells in leukemia often reflect the disease and its treatment and do increase infection risk, especially when neutrophils are very low. ^{[4] [3]}
• You can lower your risk by timely reporting of symptoms, following hygiene and food safety steps, and working with your team on preventive strategies like growth factors or prophylactic antibiotics when appropriate. [PM21] [PM13]
• Most importantly, treat any fever as urgent during low counts rapid evaluation and antibiotics can be lifesaving. ^{[11] [12] [14]}