🩸 Hematology

RDW: What It Means for Your Health

Red Cell Distribution Width measures how much your red blood cells vary in size (anisocytosis). A normal RDW means red blood cells are relatively uniform in size. An elevated RDW indicates mixed populations of small and large cells, which is a hallmark of certain anemias. RDW combined with MCV is a powerful diagnostic tool for classifying anemia type.

Full Name
Red Cell Distribution Width (RDW)
Normal Range
11.5–14.5 %
Also Known As
Red Cell Distribution Width, RDW-CV

Reference Range

LowNormal: 11.5–14.5 %High

Reference ranges may vary between laboratories, age groups, and sexes. The values shown are general adult reference ranges. Always compare your results to the specific range provided by your testing laboratory.

What Is RDW?

Red Cell Distribution Width measures how much your red blood cells vary in size (anisocytosis). A normal RDW means red blood cells are relatively uniform in size. An elevated RDW indicates mixed populations of small and large cells, which is a hallmark of certain anemias. RDW combined with MCV is a powerful diagnostic tool for classifying anemia type.

Commonly included in:

Complete Blood Count (CBC)

What Does High RDW Mean?

Above 14.5 %

Elevated RDW indicates significant variation in red blood cell size (anisocytosis). It is commonly elevated in iron deficiency anemia, B12/folate deficiency, mixed anemias, hemolytic anemias, and after blood transfusion. Recent research also links elevated RDW to increased cardiovascular disease risk and overall mortality.

What Does Low RDW Mean?

Below 11.5 %

A low RDW is rarely clinically significant and simply means that red blood cells are very uniform in size. This is generally considered normal.

Related Biomarkers in Hematology

Hemoglobin
Oxygen-carrying protein found inside red blood cells.
Range: 12–17.5 g/dL
Hematocrit
Percentage of blood volume occupied by red blood cells.
Range: 36–50 %
WBC
Total white blood cell count measuring immune system activity.
Range: 4.5–11 10^3/uL
RBC
Total number of red blood cells in your blood.
Range: 4–5.5 10^6/uL
Platelet
Blood cells responsible for clotting and wound healing.
Range: 150–400 10^3/uL
MCV
Average size of your red blood cells.
Range: 80–100 fL

Track Your RDW Over Time

Upload your blood test results to Hemoly and see how your RDW levels change over time. Get trend analysis, educational insights, and a personal health timeline.

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Medical Disclaimer

This information is for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult a qualified healthcare professional for interpretation of your blood test results and before making any health decisions.