This Mentzer index calculator helps to distinguish between the two common causes of anemia: thalassemia vs iron deficiency anemia. To use the tool, you need only basic morphology, such as red blood cell count (the amount of erythrocytes in one mm3) and the mean corpuscular volume (MCV) of an erythrocyte.

Below, you'll find more information on what thalassemia is, what causes thalassemia, thalassemia vs. anemia from iron deficiency, thalassemia MCV normal ranges, and instructions on using this tool.

What is thalassemia? Thalassemia vs iron deficiency anemia

Thalassemia and iron deficiency are both causes of low levels of hemoglobin (Hb), a protein in red blood cells which carries oxygen. Although symptoms of both are the same, depending on the severity of anemia, their origin is completely different:

  1. The thalassemia definition states that it's a genetic condition passed on from either one or both parents, which expresses itself as a lowered hemoglobin production. The two main types, alpha- and beta-thalassemia, differ on the location of the mutation. There are four genes for alpha globin or two genes for beta globin, and the severity of anemia depends on the number of missing genes.

    It may be diagnosed with a complete blood count, hemoglobin electrophoresis, or genetic testing to confirm the mutation.

    The disruption in globin formation does not impact the number of RBCs (red blood cells), yet they're smaller and rupture easier. Therefore in thalassemia, MCV (mean corpuscular volume) is reduced, while the RBC count remains within normal ranges.

  2. Iron deficiency anemia is caused by lack of iron, most often due to blood loss, pregnancy or an inadequate diet. Iron is crucial in hemoglobin production and, subsequently, proper oxygen transportation. As the marrow doesn't get enough iron, it produces fewer and smaller erythrocytes (microcytic). Both RBC count and MCV are reduced.

Thalassemia MCV values

The normal MCV ranges are:

  1. Adults, children, and older people: 80-95 fl.
  2. Newborns: 96-108 fl.

The unit fl stands for femtoliter.

The main difference between thalassemia vs anemia from iron deficiency is in the RBC count. In thalassemia, this parameter remains normal, while if iron levels are low, there are fewer erythrocytes than usual. If you have wondered how to test for thalassemia, this is an answer. In both types of anemia, MCV is lower than the normal range. This anemia calculator can help you find out which of these two diseases is more probable.

What is alpha thalassemia? What is beta thalassemia?

Let us briefly explain what causes thalassemia. As we mentioned above, thalassemia results from a mutation in one of the genes responsible for globin production. Two proteins (alpha and beta globin) form hemoglobin, and depending on which globin is impaired, we can distinguish two different types of thalassemia definitions:

  1. Alpha thalassemia - The alpha globin protein is missing or altered; this most often occurs in the region of Southeast Asia, the Middle East, China, and Africa.
  2. Beta thalassemia - A gene defect in the beta-globin protein; most often affects people in the Mediterranean.

When we look at the type of inheritance, there are:

  1. Thalassemia major - Both genes have a defect, which means that both parents have passed on the mutated gene.
  2. Thalassemia minor - Only one gene is transferred from the parents. Most often, they do not present any symptoms, yet carry the disease.

Anemia consequences

Anemia symptoms differ depending on the severity, i.e., how high the hemoglobin levels are.

Hemoglobin levels
12-16 g/dl for women
14-18 g/dl for men
≥10 g/dl
8-10 g/dl
6.5-7.9 g/dl
Life threatening
<6.5 g/dl

At first, the symptoms may be subtle, yet once anemia becomes more severe, they become more visible. What to look for?

  1. Fatigue and generalized weakness throughout the day. As RBCs carry less oxygen, less O2 reaches your tissues, including muscles, impairing their function and making them weaker.
  2. Pale or yellowish skin.
  3. Irregular heartbeats, palpitations or maybe a really fast heartbeat.
  4. Difficulties catching your breath even during easy exercises.
  5. Dizziness or lightheadedness, headaches, often due to lowered blood pressure.
  6. Chest pain.
  7. Feeling cold, especially in the hands and feet, caused by weakened blood circulation.
  8. Problems with concentration, work, and studying.
  9. Pica syndrome. This one is interesting! Low iron levels in your body cause urgent cravings for weird foods, like chalk, ice, clay, or dirt.

Mentzer index calculator and formula

This anemia calculator is based on a simple calculation from two values: mean corpuscular volume, MCV (given in femtoliters - fl) and red blood cell count, RBC (in a million per mm3). The Mentzer index formula is the following:

Mentzer index = MCV / RBC

So, how to test for thalassemia? If the result is <13, thalassemia is more probable. Otherwise, if the result is >13, then iron deficiency anemia is the most probable. If the index equals 13, the test results are inconclusive. Our Mentzer index calculator will display an appropriate comment regarding your result.


How to calculate Mentzer index?

To calculate Mentzer index, divide MCV by RBC. The Mentzer index formula is:

index = MCV / RBC

where MCV is the mean corpuscular volume given in femtoliters, and RBC is the red blood cell count in a million per mm³. The index higher than 13 indicates an iron deficiency, while thalassemia causes this index to be lower than 13.

How does thalassemia cause anemia?

Thalassemia is a genetic disease inherited from either one or both parents. It impairs globin synthesis, either affecting the alpha- or beta-globin. The body still produces a normal amount of red blood cells, yet they're smaller and more easily ruptured. As a result, oxygen transportation is worse.

Is thalassemia hemolytic anemia?

Yes, thalassemia is hemolytic anemia. It means that red blood cells are destroyed more easily, and faster than they're produced.

What MCV is in iron deficiency anemia?

In iron deficiency anemia, MCV levels are lower than 80 fl. The normal range is between 80 – 95 fl. Low MCV means that the red blood cells are smaller than normal. On the contrary, high MCV is present in people with vitamin B12 deficiency anemia.

Dominika Miszewska, PhD candidate
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