RDW
RDW measures how much your red blood cells vary in size. It helps distinguish between types of anemia.
Category: Complete Blood Count
Also known as: rdw, red cell distribution width, rdw-cv
Reference range: 11.5–14.5 % (Source: ABIM)
Standard unit: %
High values may indicate
High RDW (anisocytosis) may indicate iron deficiency, vitamin B12 or folate deficiency, mixed anemias, or recent blood transfusion.
Low values may indicate
Low RDW is generally normal and indicates uniform red blood cell size.
Frequently asked questions
- What is a normal RDW level?
- A typical reference range for RDW is 11.5–14.5 % (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is RDW measured in?
- RDW is most commonly reported in %. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do RDW reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track RDW over time?
- Yes. Upload results from any lab and BloodId charts your RDW over time against its reference range, so you can see whether the trend is rising, falling, or stable.