Understanding RDW: Normal vs Optimal Ranges

?What is RDW?

RDW (red cell distribution width) measures the variation in the size of red blood cells. A high RDW means there is greater variability in cell size (anisocytosis). This can indicate mixed deficiencies, early iron or B12/folate deficiency, or haemolytic conditions.

!Why It Matters

RDW is one of the most underappreciated CBC indices. Research has shown that elevated RDW is a powerful predictor of all-cause mortality — even in people without obvious anaemia. A high RDW with normal haemoglobin may indicate mixed deficiency states (iron + B12 simultaneously) where their effects on MCV cancel each other out. It is also elevated in chronic inflammatory conditions.

Reference Ranges

Lab normal ranges may vary between laboratories. Optimal and longevity targets are based on research literature and should be interpreted with your physician.

Symptoms of Imbalance

• High RDW alone causes no symptoms

How to Improve Your Levels

• 1Identify and correct mixed nutritional deficiencies
• 2Check ferritin, B12, and folate if RDW is elevated
• 3Treat underlying inflammatory conditions

When to Test

Part of complete blood count. Interpret in context of other CBC indices.

Related Biomarkers