Clarilab

Blood count

RDW test

Also called red cell distribution width

How much your red cells vary in size.

Typical range
11.5–14.5%.
Usual recheck
About 3 months when out of range

Why it's done

A high RDW with small cells points towards iron deficiency.

What a high result can mean

Mixed cell sizes: early iron, B12 or folate deficiency, or recent blood loss.

Got a report with RDW?

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More blood count tests

Complete blood count (CBC)Counts your red cells, white cells and platelets, and measures haemoglobin. HemoglobinThe protein in red blood cells that carries oxygen. White blood cellsThe cells that fight infection. PlateletsCell fragments that help blood clot. Red blood cellsThe number of oxygen-carrying red cells. Hematocrit (HCT/PCV)The share of your blood made up of red cells.