# Mentzer Index Calculator

URL: https://speedycalculator.com/calculators/health/mentzer-index/
Last updated: 2026-10-30

> The Mentzer index calculator divides MCV by the red cell count to help tell thalassaemia trait (index below 13) from iron-deficiency anaemia (above 13) in people with small red blood cells.

## Inputs

- MCV (fL)
- Red blood cell count (×10¹²/L)

## Results

- Mentzer index
- Suggests

## Formula

```
Mentzer index = MCV (fL) ÷ RBC (×10¹²/L)
< 13: thalassaemia trait more likely · > 13: iron deficiency more likely
```

## Explanation

In thalassaemia trait the marrow makes many small red cells, so the count is normal or high; in iron deficiency it makes fewer cells. The index is a quick screen – iron studies and haemoglobin electrophoresis confirm the diagnosis.

### How to use the Mentzer Index Calculator

- **MCV**
- **Red blood cell count**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter MCV and red cell count.

### Inputs explained

FieldWhat to enterMCVIn fLRed blood cell countIn ×10¹²/L

### Example values

How the main result changes when **MCV** changes and everything else stays at the example values above:

MCV (fL)Mentzer index519.16812.18515.210218.2
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — MCV: 68 fL; Red blood cell count: 5.6 ×10¹²/L.

Results — **Mentzer index = 12.1**; Suggests = Thalassaemia trait more likely.

## Key terms

- **Thalassaemia trait**: Carrier state of thalassaemia with mild microcytosis.

## FAQ

**How accurate is the Mentzer index?**
Useful as a first screen, but it misclassifies some patients.

**Can both conditions occur together?**
Yes – iron deficiency can coexist with thalassaemia trait.

**What confirms thalassaemia?**
Haemoglobin electrophoresis or HPLC, and sometimes genetic testing.


## Sources

- [Mentzer WC Jr. Differentiation of iron deficiency from thalassaemia trait. Lancet, 1973](https://pubmed.ncbi.nlm.nih.gov/4123004/)