Interpret Your Red Cell Distribution Width Results
Enter your RDW value below and get an instant, free AI interpretation — a plain-English explanation checked against WHO/IFCC reference ranges.
Medical Disclaimer
This AI-generated interpretation is for educational purposes only and does not constitute medical advice, diagnosis, or treatment. Results may vary based on individual health factors not captured here.
Always consult a qualified healthcare professional before making any health decisions. Read full disclaimer →
Red Cell Distribution Width Normal Ranges
RDW measures the variability in red blood cell size (anisocytosis).
| Reference Range | Unit | Notes |
|---|---|---|
| 11.5 – 14.5 | % | RDW-CV (coefficient of variation) |
Why Doctors Order the Red Cell Distribution Width Test
RDW is particularly useful for distinguishing iron deficiency anemia (high RDW, low MCV) from thalassemia trait (normal RDW, low MCV). In iron deficiency, new small cells appear alongside old normal cells, creating size variation.
How to Enter Your RDW Result
Enter your RDW value in %, exactly as shown on your lab report.
What a Low or High RDW Can Be Associated With
Below the reference range
- Not clinically significant (low RDW means cells are uniformly sized)
Above the reference range
- Iron deficiency anemia (most common cause)
- Vitamin B12 deficiency
- Folate deficiency
- Mixed nutritional deficiency
- Hemolytic anemia (with reticulocytosis)
These are common associations, not a diagnosis. A single result is read alongside your symptoms, history and other tests — discuss it with your doctor.
What Can Change Your RDW Result
Before you read too much into a result, consider whether any of these applied:
- Recent blood transfusion (introduces different-sized cells)
- Reticulocytosis (young cells are larger, increasing variation)
- Cold agglutinins (clumps may be miscounted)
Preparing for the test: No preparation needed. Automatically calculated from CBC.
Symptoms That Often Prompt RDW Testing
- Symptoms of the underlying anemia type
- Fatigue
- Pallor
Want the full clinical guide to Red Cell Distribution Width?
Reference ranges, causes, symptoms, preparation, and FAQs.