What Is a RDW Blood Test? An RDW blood test – also known as a red blood cell distribution width blood test – is a measure of the difference in your red blood cells’ size and volume. RDW is one part of ...

Talk to your doctor if you have signs of anemia, such as excessive fatigue, because it may be helpful to have a red cell distribution width (RDW) along with a complete blood count (CBC) test. Be ...