Mentzer Index
Enter mean corpuscular volume (MCV) and red blood cell (RBC) count to calculate the Mentzer index and interpret microcytic anemia etiology.
Use the RBC count reported in millions per microliter.
Mentzer index
12.36
Suggestive of thalassemia trait
Mentzer index <13 often points toward thalassemia trait. Order hemoglobin electrophoresis or genetic testing to confirm.
How to Use This Calculator
Collect CBC parameters
Obtain MCV and RBC count from a recent complete blood count performed on the same specimen.
Enter values in native units
Use MCV in femtoliters and RBC count in millions per microliter as reported by the laboratory.
Interpret with clinical context
Use Mentzer index along with ferritin, transferrin saturation, RDW, and family history to differentiate iron deficiency from thalassemia trait.
Formula
Mentzer index = MCV (fL) ÷ RBC count (×10⁶/µL)
Interpretation: <13 suggests thalassemia trait; >13 suggests iron deficiency anemia.
Full Description
The Mentzer index is a quick screening tool in microcytic anemia. By dividing MCV by RBC count, it highlights whether microcytosis stems from low RBC production (iron deficiency) or from microcytic RBCs with preserved counts (thalassemia trait). Use it as part of a broader diagnostic workup, recognizing that overlap can occur, especially with combined deficiencies or chronic disease.
Frequently Asked Questions
Is Mentzer index reliable in children?
Yes, it is frequently used in pediatrics. Confirm with iron studies and hemoglobin electrophoresis when results are borderline.
What if the patient has both iron deficiency and thalassemia?
Mixed disorders can blur the interpretation. In such cases, rely on ferritin, genetic testing, and clinical findings.
Can RDW help alongside Mentzer index?
Yes. Elevated RDW favors iron deficiency, whereas a normal RDW is more consistent with thalassemia trait.
Is this applicable to macrocytic anemias?
No. Mentzer index is designed for microcytic anemia evaluation. Use other algorithms for macrocytosis.