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Red Cell Distribution Width (RDW) Analyzer

Written by the Elysia Tools team · Last updated：2026-08-08

This tool is for informational purposes only and does not constitute medical, financial, or legal advice; consult a qualified professional for advice.

Analyze Red Cell Distribution Width (RDW) with MCV to help differentiate anemias. RDW-CV reference ≈ 11.5–14.5%, RDW-SD ≈ 39–46 fL (lab-dependent). Elevated RDW reflects anisocytosis. Classic Bessman patterns: high RDW + low MCV → iron deficiency anemia (IDA), which raises the RDW early — before MCV/Hb fall; normal RDW + low MCV → thalassemia trait (uniform microcytosis). Other patterns: high RDW + high MCV → megaloblastic anemia (B12/folate), MDS, drugs, hemolysis with reticulocytosis, preleukemia, or mixed populations (combined iron + B12 deficiency, post-transfusion); high RDW + normal MCV → early/mixed nutritional deficiency, dimorphic anemia, marrow recovery; normal RDW + normal MCV → anemia of chronic disease is classically normocytic. Interpret with Hb, ferritin, Hb electrophoresis, and clinical context. Based on Bessman 1983 and Teixeira 2014. Not medical advice.

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Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category
Health
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes

Overview

The Red Cell Distribution Width (RDW) Analyzer evaluates RDW-CV or RDW-SD together with MCV to identify common red-cell size patterns that may help differentiate anemias. Results use laboratory-dependent reference ranges and are not medical advice.

When to use

  • Compare RDW with MCV when reviewing a complete blood count for anemia patterns.

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Screen for patterns such as high RDW with low MCV or normal RDW with low MCV.
  • Use as an initial interpretation aid before reviewing ferritin, Hb electrophoresis, hemoglobin, and clinical findings.

    • How it works

    1. 1Select the RDW form: RDW-CV in percent or RDW-SD in fL.
    2. 2Enter the measured RDW value and MCV in fL.
    3. 3The analyzer compares RDW and MCV with approximate reference ranges and classifies the pattern.
    4. 4The result is returned as JSON with RDW status, MCV category, pattern category, and model information.

    Use cases

    • Reviewing microcytic anemia patterns by combining RDW with MCV.
    • Comparing possible iron deficiency and thalassemia-trait patterns.
    • Organizing CBC findings before follow-up laboratory evaluation.

    Examples

    1. Iron deficiency pattern

    Clinician reviewing a CBC

    Background

    A CBC shows an RDW-CV of 18% and an MCV of 74 fL.

    Problem

    Classify the relationship between elevated RDW and low MCV.

    How to use

    Select RDW-CV (%), enter 18 for RDW and 74 for MCV, and keep decimal places at 1.

    {"rdwForm":"cv","rdw":18,"mcv":74,"decimalPlaces":1}

    Outcome

    The JSON result reports elevated RDW with low MCV and classifies the pattern as high RDW plus low MCV, consistent with dimorphic microcytosis. Ferritin and other clinical data are needed for confirmation.

    2. Thalassemia-trait pattern

    Laboratory learner

    Background

    A CBC shows an RDW-CV of 13% and an MCV of 68 fL.

    Problem

    Determine whether the microcytosis is accompanied by increased red-cell size variation.

    How to use

    Select RDW-CV (%), enter 13 for RDW and 68 for MCV, and keep decimal places at 1.

    {"rdwForm":"cv","rdw":13,"mcv":68,"decimalPlaces":1}

    Outcome

    The JSON result reports normal RDW with low MCV and classifies the pattern as uniform microcytosis, a classic thalassemia-trait pattern. Ferritin and Hb electrophoresis may be needed for evaluation.

    FAQ

    What inputs does the RDW Analyzer require?

    It requires an RDW form, an RDW value, and an MCV value in fL. Decimal places are optional.

    What is the difference between RDW-CV and RDW-SD?

    RDW-CV is the coefficient of variation reported as a percentage. RDW-SD is the distribution width reported in fL.

    What does a high RDW with low MCV suggest?

    It is a classic pattern of iron deficiency anemia, although other mixed or dimorphic processes are possible.

    What does a normal RDW with low MCV suggest?

    It indicates relatively uniform microcytosis, a classic pattern associated with thalassemia trait.

    Is this analyzer a medical diagnosis?

    No. Interpret the result with hemoglobin, ferritin, Hb electrophoresis, laboratory ranges, and clinical context.

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