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Hematology

Red cell distribution width

How much your red cells vary in size, expressed as a percentage spread around the average.

Unit %Typical adult range 11.5–14.5 %
What it is

How much your red cells vary in size, expressed as a percentage spread around the average.

Why it matters

It often moves before MCV does, which makes it the earliest index to shift in developing iron deficiency.

Reading the number

A raised RDW with a normal MCV means two populations of cells are averaging out -- classically iron deficiency and B12 deficiency together. A high value is a prompt to look at the rest of the panel, never a finding on its own.

What moves it
iron storesB12 and folate statusrecent transfusionrecent bleeding
Read alongside
Mean corpuscular volumeFerritinVitamin B12HemoglobinRed blood cells
When to raise it

Worth mentioning a rise alongside a hemoglobin that is drifting down.

Tracking only, not a diagnosis. The range above is a typical adult reference range — the range printed by the lab that ran your test is the one that applies to you. Discuss anything that concerns you with your doctor.

Also known as

On a report in another language.

A lab report names this analyte in its own language. Vitals Vault recognises each of these and files them all under Red cell distribution width.

RDWAmplitude de Distribuição EritrocitáriaErythrozytenverteilungsbreite

Track your red cell distribution width over time.

Red cell distribution width is one of 165 analytes Vitals Vault charts over time. Import a lab report in any language and this number lands on a timeline only you can read.

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Tracking only. This app is not medical advice. Always discuss results and future analysis with your doctor.

Catalog entry last updated 2026-08-27. Browse all 165 metrics.