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White blood cell differential

Also called: WBC differential, CBC with diff, Differential count

A white blood cell differential counts each type of white blood cell. It helps show whether a problem looks like a bacterial infection, a virus, an allergy, or something else.

SampleA small tube of blood from a vein in your arm
Fasting?Usually not needed
ResultsOften the same day
Good to knowOne result rarely tells the whole story. Your provider looks at your results together with your symptoms, exam, and other tests.

What the test is

It's usually done with a CBC.

Results are given as a percentage of all white cells and as an absolute count.

What it measures

  • Neutrophils, which fight bacteria
  • Lymphocytes, which fight viruses
  • Monocytes, which clean up damaged cells
  • Eosinophils, which rise with allergies and parasites
  • Basophils, which play a role in allergic reactions

Why it's done

  • To look into a high or low white count
  • To check for infection, allergy, or inflammation
  • To monitor blood disorders and some treatments

Getting ready and what happens

  • No special preparation is needed.

How the test is done

  • A health worker cleans the skin, puts a band around your arm, and draws blood from a vein with a small needle. It takes a few minutes.

What the results mean

ResultTypical range for adults
NeutrophilsAbout 1,500 to 8,000 per microliter (about 40% to 70%)
LymphocytesAbout 1,000 to 4,800 per microliter (about 20% to 40%)
MonocytesAbout 2% to 8%
EosinophilsAbout 1% to 4%
BasophilsAbout 0.5% to 1%

Normal ranges vary from lab to lab and can differ by age, sex, and pregnancy. Your report lists your lab's own range next to each result. A result a little outside the range is often not a problem.

High neutrophils

Common with bacterial infections, stress, injury, and steroid medicines.

Low neutrophils

Can follow viral infections or be caused by some medicines or chemotherapy. Very low counts raise infection risk.

High lymphocytes

Common with viral infections like mono. Lasting high counts in older adults can need more testing.

High eosinophils

Often from allergies, asthma, eczema, some medicines, or parasites.

When a result needs quick action

Call 911Fever of 100.4°F or higher with a very low neutrophil count, especially during chemotherapy

Questions to ask your provider

  • What do my results mean for me?
  • Do I need to repeat this test or have other tests?
  • What could be causing my result?
  • Should the test be repeated in a few weeks?

Risks

A blood draw is very safe. You may have slight pain or a small bruise where the needle went in.

Related conditions

Related tests

Sources

Last updated 2026-11-13.