What is Red Cell Distribution Width? Your Complete Guide
Measures how much variation there is in the size of your red blood cells. A high number means your red blood cells are very uneven in size.
💡Simply Explained
RDW checks if all your red blood cells are the same size or if they're all different sizes — like checking if all the balls in a ball pit are the same size or a mix of big and small ones.
📏Normal Range
Typical reference range. Your lab may use slightly different values.
⬆️What High Red Cell Distribution Width Means
Possible Causes
- Iron deficiency anemia (most common)
- B12 or folate deficiency
- Mixed nutritional deficiency
- Recent blood transfusion
- Early response to iron/B12 treatment
Foods That Can Help
- Depends on the underlying cause — iron, B12, or folate rich foods accordingly
⬇️What Low Red Cell Distribution Width Means
Possible Causes
- Generally not clinically significant
- Very uniform red blood cells (normal variant)
Foods That Can Help
- No specific dietary changes needed
🏃Lifestyle Actions
If Your Red Cell Distribution Width Is High
- Get iron, B12, and folate tested to find the root cause
- High RDW with normal MCV may indicate early iron deficiency
If Your Red Cell Distribution Width Is Low
- No action needed — uniform red blood cells are normal
🩺When to See a Doctor
High Red Cell Distribution Width
Not urgent on its own. Use it as a clue alongside other CBC values to guide further testing.
Low Red Cell Distribution Width
Low RDW is not a concern.
🎯Did You Know?
RDW can help distinguish iron deficiency (high RDW) from thalassemia trait (normal RDW) — two conditions that otherwise look very similar on a blood test!
❓Frequently Asked Questions
What is Red Cell Distribution Width?
RDW checks if all your red blood cells are the same size or if they're all different sizes — like checking if all the balls in a ball pit are the same size or a mix of big and small ones.
What is the normal range for Red Cell Distribution Width?
The typical normal range for Red Cell Distribution Width is 11.5–14.5 %.
What causes high Red Cell Distribution Width?
Iron deficiency anemia (most common). B12 or folate deficiency. Mixed nutritional deficiency.
What causes low Red Cell Distribution Width?
Generally not clinically significant. Very uniform red blood cells (normal variant).
How can I check my Red Cell Distribution Width levels?
You can check your Red Cell Distribution Width levels with a routine blood test. Upload your lab report to ScanHealth for an instant, plain-language explanation.
Check Your Red Cell Distribution Width Results Instantly
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Upload Your ReportThis guide is for informational purposes only and does not constitute medical advice. Reference ranges may vary by lab. Always consult a qualified healthcare provider for diagnosis and treatment.