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Red Cell Distribution Width
Abbreviation: RDW
Panel: Complete Blood Count (CBC) · All complete blood count tests
Typical adult reference range
| Conventional units | 11.5–14.5 % |
| SI units | 11.5–14.5 % |
Ranges vary between laboratories and methods — compare your result with the range printed on your own report.
What a high or low result can mean
High red cell distribution width: high values can be seen in iron, vitamin B12, or folate deficiency and after transfusion.
These are associations, not a diagnosis: the same result can have several causes, and your clinician interprets it with the rest of your results and history.
Good to know
Measures variation in red cell size.
Related tests — Complete Blood Count (CBC)
Please note: Reference ranges vary between laboratories, and between the methods and instruments they use — the range printed on your own report is the one your result should be compared with. A result outside the range is not by itself a diagnosis, and a result inside it does not rule out illness. These pages are an educational summary, not medical advice: always discuss your results with the clinician who ordered them, who can interpret them in the context of your health and history.