Know Your Blood Parameter : Red Cell Distribution Width

1. Parameter Name 

Red Cell Distribution Width (RDW)

2. Test Type 

Blood

3. Normal Range

• RDW-CV: 11.5% – 14.5%

• RDW-SD: 39 – 46 fL (some labs may vary)

  
  

4. High Levels Indicate 

Increased variability in red blood cell size — seen in iron deficiency anemia, vitamin B12/folate deficiency, recent blood loss, or bone marrow disorders like myelodysplastic syndromes.

5. Low Levels Indicate 

Usually not clinically significant; may indicate uniform red cell size which could still be abnormal if all are uniformly small (microcytic anemia).

6. Why It's Tested 

To assess red blood cell size variation, aiding in the diagnosis and classification of different types of anemia.

7. Associated Symptoms (if abnormal) 

Fatigue, weakness, pallor, dizziness — symptoms depend on the underlying cause of anemia.

8. What To Do If Abnormal 

Follow up with iron studies, vitamin B12/folate levels, or reticulocyte count based on clinical suspicion. Consult a physician for appropriate diagnosis and treatment.

9. Common Conditions Related 

Iron deficiency anemia, pernicious anemia, thalassemia, chronic liver disease.

10. Nutrition or Lifestyle Connection 

Adequate intake of iron, B12, folate, and overall balanced nutrition is essential. Supplementation may be needed based on deficiencies.

11. References (APA Format)

• Pagana, K. D., & Pagana, T. J. (2021). Mosby’s diagnostic and laboratory test reference (15th ed.). Elsevier.

• MedlinePlus. (2023). Red Cell Distribution Width (RDW). U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/rdw-red-cell-distribution-width/

• Mayo Clinic. (2022). Complete blood count (CBC). https://www.mayoclinic.org/tests-procedures/complete-blood-countChernecky, C. C., & Berger, B. J. (2013). Laboratory Tests and Diagnostic Procedures (6th ed.). Saunders.