Anemia is a state of reduced hemoglobin concentration in the blood with a normal or reduced number of erythrocytes. In such a condition, the blood's ability to transport oxygen is reduced due to the reduced concentration of hemoglobin, which causes tissue hypoxia, which triggers numerous compensatory mechanisms. According to the morphological classification, we distinguish between normocyticnormochromic, microcytic-hypochromic and macrocytic anemias. Based on the mechanism of anemia, a large number of anemias are distinguished. Some of them are the result of disorders of erythrocyte maturation, increased or accelerated decomposition of erythrocytes, hematopoietic stem cell diseases. The most common form of anemia is pernicious anemia, which is caused by iron deficiency. Laboratory diagnosis of anemia includes everyday basic and specific hematological and biochemical tests, cytological tests, and more recently molecular diagnostics. Basic tests, such as KKS with determination of reticulocyte indicators and morphological examination of peripheral blood smear, perform a primary search, respectively determine the presence of anemia and gain insight into the activity of erythrocytopoiesis.