RDW (Red Cell Distribution Width)
Reviewed
A red cell distribution width test measures how much the volume and size of your red blood cells vary. It is often part of a complete blood count and helps diagnose or determine the cause of anemia and other blood disorders.
Preparation and collection
No special preparation is necessary.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- There is very little risk to a blood test; slight pain or bruising at the needle site may occur but usually resolves quickly.
- Normal RDW does not rule out anemia or other conditions; further evaluation is needed.
- RDW results are interpreted together with other blood tests, not in isolation.
What to do next
Discuss your RDW results with your healthcare provider, who will consider them along with other tests to determine if further evaluation or treatment is needed.
Evidence source
U.S. National Library of Medicine: RDW (Red Cell Distribution Width)