What Causes High Red Cell Distribution Width (RDW) Levels?

High red cell distribution width (RDW) levels may act as an early indicator of nutritional deficiencies, such as low folate levels, according to Medscape. In addition, it can indicate that someone is not getting enough vitamin B12 or iron.

Elevated RDW levels can also indicate:

  • Aplastic anemia
  • Chronic liver disease
  • Chemotherapy, antiviral and alcohol use
  • Immune hemolytic anemia

Doctors can use RDW test results to distinguish between uncomplicated anemia and uncomplicated thalassemia. However, the results act as a platform for further tests, and therefore are not definitive. High RDW levels also point towards the cause of megaloblastic anemia, allowing doctors to determine whether the cause is a folate or vitamin B12 deficiency.