Red Cell Distribution Width (RDW): A measure of the variation in size between red blood cells. Useful in evaluating the cause of, and therapy for, anemia. Increased values may indicate a number of things including vitamin B12, folic acid, or iron deficiency.

Llewellyn, William (2011-08-04). Anabolics E-Book Edition (Kindle Locations 2897-2899). Molecular Nutrition. Kindle Edition.