A high RDW coefficient of variation (RDW-CV) means your red blood cells vary in size, typically above 14.5%. This measurement reflects the range of your red blood cell sizes, expressed as a percentage.
Red blood cell distribution width (RDW) measures the variation in size of your red blood cells. The coefficient of variation (CV) standardizes this measurement as a percentage, allowing comparison across different blood tests. A higher percentage indicates greater variability in cell size.
| Type | Measurement | Typical Range |
|---|---|---|
| RDW-CV | Percentage | 11.5%-14.5% |
| RDW-SD | Femtoliters (fL) | 41-51 fL |
While RDW-CV is more commonly reported, RDW-SD measures absolute size variation in femtoliters. Both indicate red blood cell size variability but use different units.
A high RDW-CV often accompanies anemia, particularly iron-deficiency anemia or vitamin B12 deficiency. It can also signal chronic diseases, inflammation, or bleeding. Doctors use RDW alongside other blood tests, like hemoglobin and mean corpuscular volume (MCV), to diagnose and monitor conditions.
For example, a patient with fatigue and pallor might have low hemoglobin, high RDW-CV, and low MCV, suggesting iron-deficiency anemia. Treatment with iron supplements typically normalizes these values over time.
Some assume high RDW-CV always indicates severe illness. However, it can also result from benign causes like recent blood donation or pregnancy. Always evaluate it alongside other blood test results and clinical symptoms.
During my annual check-up, my doctor noted an elevated RDW-CV. Further testing revealed mild iron deficiency, likely due to dietary changes. Adjusting my diet normalized the RDW-CV within months, confirming its role as an early warning sign.