Complete Blood Count (CBC)

Monocytes

Also written as: absolute monocyte count, monos

The immune system's cleanup crew - white cells that clear debris and become tissue macrophages.

What it measures

The number of monocytes in the blood. Monocytes are large white blood cells that clear debris, dead cells, and microbes, and that move into tissues to become macrophages, the long-lived cleanup cells of the immune system.

Why a doctor orders it

It is reported as part of the white cell differential on a complete blood count rather than ordered by itself. Clinicians usually read it as one piece of the overall white cell picture rather than in isolation.

What is generally associated with a higher result

Broadly associated with recovery from an infection, with chronic inflammation, and with smoking. A mild, isolated rise is common and often transient. Only a persistent and marked elevation tends to prompt evaluation for blood disorders.

What is generally associated with a lower result

Broadly associated with acute infections and corticosteroid medicines. Isolated low values are generally not pursued.

Everyday things that move this number

Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:

  • Recovering from a recent infection, when counts commonly rise
  • Smoking
  • Corticosteroid medicines
  • Physical stress
  • Time of day

Questions to take to your appointment

  • Is this an isolated finding, or part of a broader pattern across the white cell types?
  • Could an infection I recently got over explain it?
  • How does this compare with my previous differentials, if I have any on file?

Build a printable questionnaire with your own results →

Where to read more

MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .

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