Red Cell Distribution Width (RDW)
- Sample Type
- Standard
- Fasting
- No
- Unit
- %
RDW is a numerical measure of the variation in size (volume) of red blood cells, a condition known as anisocytosis. Within a Complete Blood Picture, RDW is a vital tool for the differential diagnosis of anemia. While the MCV (Mean Corpuscular Volume) tells you the average size, the RDW tells you how much the sizes vary. It is often the first indicator of nutritional deficiencies (Iron, B12, or Folate) before the hemoglobin level even drops.
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Enter your lab result to see where you stand compared to the standard reference range.
Why Context Matters
RDW can be falsely elevated if there are fragmented RBCs, cold agglutinins (clumping), or if the patient has recently received a blood transfusion (mixing donor and recipient cells of different ages/sizes).
Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.
Clinical References
Source-of-truth databases and clinical guidelines for Red Cell Distribution Width (RDW):
Official Sources
Research & Guidelines
Related Indicators
Medically Reviewed by Dr. Binoy Babu, MBBS
Board Certified Doctor • 10+ Years Clinical Experience
Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.
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