Mentzer Index Calculator for Anemia

Clinical Calculator

Mentzer Index Calculator

Use this screening calculator to help differentiate iron deficiency anaemia from beta-thalassaemia trait using complete blood count values.

Formula: Mentzer Index = MCV ÷ RBC count
How to Use the Calculator+
  1. Enter the patient’s MCV value in femtolitres (fL).
  2. Enter the patient’s RBC count in ×1012/L or million/µL.
  3. Select Calculate Mentzer Index to view the index and screening interpretation.

Calculate the Mentzer Index

Unit: fL
Unit: ×1012/L or million/µL

Frequently Asked Questions

What does the Mentzer Index measure?+
The Mentzer Index compares mean corpuscular volume with the red blood cell count to help screen microcytic anaemia patterns.
What does a Mentzer Index below 13 suggest?+
A value below 13 is commonly used as a screening clue that beta-thalassaemia trait may be more likely.
What does a Mentzer Index above 13 suggest?+
A value above 13 is commonly used as a screening clue that iron deficiency anaemia may be more likely.
Is the Mentzer Index diagnostic?+
No. It is a screening tool and should be interpreted together with history, examination, ferritin, iron studies, blood film, and thalassaemia testing.
What happens when the index is exactly 13?+
An index of exactly 13 is considered borderline and requires careful interpretation with confirmatory investigations.
Sensitivity and Specificity Reminder+

Reported performance varies according to study population, age group, pregnancy status, and local prevalence of iron deficiency anaemia and thalassaemia trait.

One commonly cited study in pregnant women reported sensitivity/specificity of 91% / 83% for iron deficiency anaemia and 83% / 91% for beta-thalassaemia trait.

Use the result together with clinical assessment and confirmatory investigations, particularly when the result is borderline or the clinical picture does not fit.

References and Clinical Notes+
  • Mentzer WC. Differentiation of iron deficiency from thalassaemia trait. Lancet. 1973.
  • Interpret results together with complete blood count indices, peripheral blood film, ferritin, iron studies, haemoglobin analysis, and clinical assessment.
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