What is the relationship between Red Cell Distribution Width (RDW) and iron deficiency?

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Last updated: April 14, 2025 • View editorial policy

From the Guidelines

RDW is a useful indicator of iron deficiency, particularly when its levels are high, as it reflects the variation in size of red blood cells, which increases in iron deficiency anemia. According to the European Consensus on the Diagnosis and Management of Iron Deficiency and Anaemia in Inflammatory Bowel Diseases 1, a wide size range of red cells, indicated by a high RDW, can help identify iron deficiency, especially in situations where microcytosis and macrocytosis co-exist, resulting in a normal MCV. Key points to consider when evaluating RDW in relation to iron deficiency include:

  • RDW is an indicator of the variation in size of red blood cells, which can be elevated in iron deficiency anemia
  • A high RDW can precede other changes in iron deficiency and can be detected before hemoglobin levels fall significantly
  • RDW should be interpreted alongside other iron parameters like ferritin, transferrin saturation, and hemoglobin levels for a complete assessment of iron status
  • An elevated RDW combined with low MCV strongly suggests iron deficiency anemia
  • Regular monitoring of RDW can help track response to iron supplementation therapy, as noted in the context of managing iron deficiency in inflammatory bowel diseases 1.

From the Research

RDW and Iron Deficiency

  • RDW (Red Cell Distribution Width) is a measure of variability in red blood cell size, and it is affected by iron deficiency 2, 3, 4.
  • Iron deficiency contributes to elevated RDW, and RDW can be used as a prognostic marker in chronic heart failure (CHF) patients with iron deficiency 2.
  • Studies have shown that RDW is significantly associated with transferrin saturation and C-reactive protein levels, indicating that RDW can be a useful marker for iron deficiency 2.

Relationship between RDW and Iron Deficiency

  • RDW increases with the development of iron deficiency, and it can be used to diagnose iron deficiency anaemia 3.
  • The sensitivity of RDW for the diagnosis of iron deficiency anaemia is 77.1%, and the specificity is 90.6% 3.
  • RDW is inversely related to haemoglobin level and transferrin saturation in iron deficiency anaemia patients, indicating that higher RDW values reflect more severe iron deficiency 4.

Treatment of Iron Deficiency and RDW

  • Treatment with intravenous ferric carboxymaltose (FCM) decreases RDW in iron-deficient CHF patients 2.
  • Ferrous sulfate treatment also decreases RDW and increases hemoglobin concentration in infants and children with nutritional iron-deficiency anaemia 5.
  • RDW can be used to monitor the response to iron therapy and to assess the severity of iron deficiency 2, 4.

RDW as a Prognostic Marker

  • Elevated RDW is associated with higher mortality risk in hemodialysis patients, and it is a stronger predictor of mortality than traditional laboratory markers of anemia 6.
  • RDW can be used as a prognostic marker in various clinical settings, including CHF and hemodialysis patients 2, 6.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.