About Red Cell Distribution Width
RDW (Red Cell Distribution Width) measures the variability in red blood cell size — a high RDW means your cells vary widely in size (anisocytosis), which is an early sign of nutritional deficiency or mixed anaemia. RDW rises early in iron, B12, and folate deficiency, often before haemoglobin drops to anaemic levels, making it a sensitive early-warning marker. A high RDW is also an independent predictor of cardiovascular mortality, infection severity, and all-cause mortality — reflecting underlying systemic inflammation and nutrient deficiency.