In primary care, anemia is a common clinical diagnosis in daily practice. Considering the types of anemia, iron deficiency anemia and beta thalassemia trait are among the most common causes in microcytic anemias. The Menzter Index, obtained by dividing the mean erythrocyte volume by the number of erythrocytes, is an important guiding parameter in the differential diagnosis of iron deficiency anemia and beta thalassemia trait. Not to miss the diagnosis of beta thalassemia trait is important for the prevention of complication development due to unnecessary treatment of iron deficiency anemia. In our case report, we wanted to draw attention to the fact that the same patient was treated with iron deficiency anemia many times until the diagnosis of beta thalassemia trait, but could not get a cure from the treatments. It is evaluated that these two microcytic anemia can be encountered frequently in clinical practice and Menzter Index should be taken into consideration while making differential diagnosis.

Keywords: Thalassemia, anemia, iron deficiency, Mentzer index