What Are Granulocytes on a Blood Test?

What it means

Granulocytes are white blood cells that carry tiny packets, called granules, inside them. Under a microscope these packets look like grains, which gives the cells their name. There are three kinds: neutrophils, eosinophils and basophils. Neutrophils are by far the most common, so a granulocyte count mostly reflects them.

Some blood count machines report granulocytes as one group instead of listing each type separately. When you see the word on a complete blood count (CBC), the lab is telling you how many of these cells it found, usually as a number per volume of blood and as a percentage of all white cells. A related line, "immature granulocytes" (IG), counts younger cells that have left the bone marrow early.

Granulocytes are not the same as lymphocytes or monocytes, the other main white cell groups, which have no obvious granules. A granulocyte result and a neutrophil result on the same report are often close to each other, but they are not identical.

Where you may see it

• The white cell differential section of a complete blood count (CBC)
• Printouts from smaller clinic analyzers that list "GRAN" or "GRA%" next to lymphocytes and monocytes
• Hospital blood results that add an "Immature granulocytes" or "IG%" line