Red Cell Distribution Width
Learn about RDW for red blood cell size variation and anemia classification. Monitor blood health diversity patterns effectively.
What is Red Cell Distribution Width?
Red Cell Distribution Width (RDW) measures the variation in red blood cell size within your blood sample. This parameter indicates how uniform your red blood cells are, with higher values reflecting greater size variation (anisocytosis). RDW is particularly valuable for differentiating between various types of anemia.
Why is it Tested?
Doctors order RDW as part of every complete blood count to help classify anemia types, assess nutritional deficiencies, and evaluate bone marrow function. It’s especially useful for distinguishing iron deficiency anemia from thalassemia and monitoring treatment response in various blood disorders.
Normal Ranges
Reference ranges vary by lab, but general adult guidelines:
- Adults: 11.5–14.5%
Normal RDW values indicate relatively uniform red blood cell sizes, reflecting stable red cell production and adequate nutrition.
Reference ranges vary by authority. Track yours across multiple standards with automatic unit conversions in LabsVault.
What do Abnormal Results Mean?
Abnormal results are not a diagnosis. Always discuss your results with a qualified healthcare provider before making any medical decisions.
Normal RDW
Normal RDW values suggest:
- Uniform red blood cell population
- Stable erythropoiesis (red cell production)
- Adequate nutritional status
- Normal hemoglobin synthesis
High RDW
Elevated RDW indicates greater red cell size variation and may suggest:
- Iron deficiency anemia (most common cause)
- Vitamin B12 or folate deficiency
- Mixed nutritional deficiencies
- Hemolytic anemia
- Recent blood transfusion
- Recovery from anemia treatment
How to Track Over Time
Tracking RDW helps monitor anemia treatment effectiveness and nutritional status. Declining RDW during iron or vitamin supplementation indicates successful treatment, while rising values may signal developing nutritional deficiencies or blood disorders requiring investigation and intervention.
Track your Red Cell Distribution Width results over time
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