Mentzer Index Calculator

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Mean Corpuscular Volume from a CBC report. Normal adult range is 80-95 fL. Values below 80 fL indicate microcytosis.
fL
Red Blood Cell count from a CBC report, in millions per microliter. Normal range: 4.7-6.1 (men), 4.2-5.4 (women).
x10⁶/μL
Used to show the appropriate normal RBC reference range.
Mentzer IndexIDA likely
13.85

MCV divided by RBC count

InterpretationIron deficiency anemia more likely
Normal RBC range4.7-6.1 x10⁶/μL (men)
MCV statusLow (microcytosis) - consistent with either IDA or thalassemia
13.85
Thalassemia likely<13IDA likely13+

Mentzer Index: 13.85 - Iron deficiency anemia more likely

  • A Mentzer Index above 13 indicates both MCV and RBC are low, a pattern typical of iron deficiency anemia where insufficient iron limits both cell size and cell production.
  • Confirm with serum ferritin (below 30 ng/mL is highly specific for iron deficiency), transferrin saturation, and TIBC.
  • Consider dietary iron intake, blood loss (gastrointestinal, menstrual), and absorption issues as root causes.
  • The Mentzer Index has approximately 91% sensitivity and 83% specificity for this interpretation (PMC9121960 meta-analysis). It is a screening tool, not a standalone diagnosis.

Next stepShare these results with a haematologist or clinician. Definitive diagnosis requires hemoglobin electrophoresis, serum ferritin, and iron studies. Do not start iron supplementation or make clinical decisions based on this index alone.

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