Reference ranges
RDW reference range
Reference ranges describe the interval a laboratory prints next to your result. They are not a diagnosis of what is “normal” for you personally — your clinician interprets results in context.
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What RDW measures
This CBC value reflects the spread, not the average, of red blood cell sizes in your sample.
Why ranges differ
Laboratories set their own reference intervals using their methods, equipment, and population data. That is why the range on your Quest report may differ from a LabCorp report — always use the interval printed on your source document.
Common units
RDW is often reported in %. Confirm units on your original report before comparing values across time.