You glance at your blood test results and notice a string of abbreviations: CBC, MCV, RDW. Some are familiar, but others feel like a secret code. RDW, in particular, sounds technical, but it actually reveals something surprisingly simple about your red blood cells. What Does RDW Mean? RDW stands for Red Cell Distribution Width . It measures how much your red blood cells vary in size. When cells are similar in size, RDW is normal. When there’s a wide mix of big and small cells, RDW goes up. Since healthy red blood cells should stay fairly consistent in size, too much variation can hint at an underlying problem. Why Do Doctors Check RDW in a Blood Test? Doctors rely on RDW to gather clues about different types of anemia and blood-related issues. On its own, RDW doesn’t give a full answer, but it becomes powerful when combined with other CBC numbers. RDW can help with: Identifying iron, folate, or vitamin B12 deficiencies. Distinguishing different types of anemia. P...