Red Blood Cell Distribution Width (RDW) by Electrophoresis

Why RDW Matters in Blood Health

Red blood cells (RBCs) are typically uniform in size, but certain health issues can cause them to vary widely. This variation, known as red blood cell distribution width (RDW), is often checked alongside other blood tests to assess overall health. For example, RDW can be elevated in conditions like anemia, iron deficiency, or vitamin B12/folate deficiencies, where red cells may be either too large or too small.

When Your Doctor Might Order This Test

Your doctor may request an RDW test if you have symptoms like fatigue, pale skin, or unusual tiredness. It’s also often included in routine blood panels when evaluating anemia or other blood-related concerns. Sometimes, RDW is checked alongside hemoglobin or other RBC measurements to get a clearer picture of your blood health.

What to Expect Before or After the Test

This test is usually done on a simple blood draw from a vein in your arm. No special preparation is needed, but you may want to avoid eating or drinking for a short time before the procedure if instructed. Afterward, you might experience mild bruising or soreness at the site, but this usually fades quickly.

Common Conditions Linked to High or Low RDW

An elevated RDW often points to conditions like iron deficiency anemia, megaloblastic anemia (due to vitamin B12 or folate deficiencies), or certain types of chemotherapy side effects. A normal RDW doesn’t rule out all causes of anemia, but it helps narrow down possibilities. Low RDW is less common but may occur in rare cases of inherited RBC disorders.