White cell count
at the bedside
- airway, breathing, circulation; full vitals including temperature
- the patient, not the number → sick or well, fever, new symptoms
- real? → compare with previous counts; a single odd value: repeat with a blood film
- neutrophils → ANC = WBC × neutrophil fraction; it is the ANC that matters
escalate now if
- fever with ANC < 0.5 ×10⁹/L, or expected to fall below → febrile neutropenia, antibiotics within the hour → fever
- WBC > 100 ×10⁹/L, or blasts on the film → hyperleukocytosis, hematology now
- new low hemoglobin or platelets with an abnormal WBC → marrow process, hematology
- high WBC with hypotension, confusion or a raised lactate → sepsis → fever, hypotension
- result on your lab’s critical-value list → see the patient now (limits differ by lab)
differentials
- high, reactive → infection, steroids, stress after surgery or a seizure, smoking, asplenia, G-CSF, epinephrine, lithium
- high, worrying → above 30 without a cause, immature cells, other cytopenias, spleen or nodes, weight loss, night sweats
- low neutrophils → chemotherapy, drugs (carbimazole or methimazole, clozapine, metamizole, TMP-SMX, sulfasalazine, beta-lactams, vancomycin), sepsis, viral illness, B12 or folate deficiency, marrow disease
- mild, stable for years, patient well → may be a Duffy-null associated neutrophil count (DANC): no added infection risk; decided by old counts and the clinical picture, not by ancestry; new, moderate or severe, or with symptoms → work it up
- falsely high → platelet clumps or nucleated red cells counted as white cells; the film settles it
- ANC 1.0–1.5 mild · 0.5–1.0 moderate · < 0.5 severe
focused check
- symptoms → fever, sore throat or mouth ulcers, cough, dysuria, abdominal pain, bruising
- drug chart → steroids, chemotherapy (date of last cycle), antithyroid drugs, clozapine, new antibiotics
- exam → mouth, skin, lines and wounds, perianal pain (no rectal exam if neutropenic), lymph nodes, spleen
send now
- repeat CBC with differential and blood film → confirms, finds blasts, clumps, toxic changes
- cultures → fever or unwell, before antibiotics
- very high WBC → RFT, urate, phosphate, calcium, LDH, coagulation (tumour lysis, DIC)
treat
hyperleukocytosis
- hematology now; leukostasis looks like hypoxia, infiltrates, confusion, headache, visual change
- IV fluids; red cell transfusion only after discussion with hematology (raises viscosity)
- potassium may be falsely high and gas PaO₂ falsely low; trust SpO₂ and a plasma potassium
neutropenia without fever
- stop a likely culprit drug (antithyroid, clozapine) with the team; do not rechallenge
- tell the nurse: any temperature ≥ 38.0 °C → call now
- ANC < 0.5 new and unexplained → hematology today
marrow process
- two or more lines low, or blasts → hematology; hemoglobin drop, platelet drop
reactive rise, patient well
- look for the source, not the number; no antibiotics for a count alone
- on steroids and well → expected; repeat with the treating team
- hand over → WBC and ANC trend, film result, drug stopped, fever trigger
evidence
Verify indication, dose, allergies, interactions, renal/hepatic function and local protocols before prescribing.
free the on-call checklist covers the whole shift on one printable page.
studying for the IM exam? the IM Rapid Review covers this in the same format. see the sample chapter.
updated Oct 2026file lab/cbc-white-cell-count