Background. The study of anemia causes in children born prematurely remains the urgent problem due to the continuous search for effective ways to prevent and treat it.Objective. The aim of the study is to study the anemia severity in premature infants, peripheral blood test results (MCV, MCH, MCHС), serum iron, and ferritin at different gestational periods.Materials and methods. 82 medical records of preterm infants were analyzed. 12 children were extremely premature (EР), 36 were very premature (VP), 27 were moderately premature (MP), and 7 were late premature (LP). The frequency of anemia, its severity, and laboratory indicators of iron metabolism were studied.Results. In EР infants, anemia developed in 100% (severe and moderate form in 16.7%, mild in 66.6%), in VP — in 94.6% (of which severe form in 5.6%, moderate — 22%, mild — 67%). Severe forms were not detected in children over 32 weeks of gestation. In infants with ЕР, the iron level at 2 weeks Me (median) 10.6 μmol/l [8.8–12.1], which is lower than in the comparison groups: VP — 15.9 [12.3–18.9] (p = 0.007), MP — 18,7 [15.8–20.5] (p = 0.0002), LP — 14,0 [16.2–23.8] (p = 0.011). Serum ferritin in the EР group is 58.4 μg/l [52.8–71.7], lower than the level in children with OH — 165.5 μg/l [77.3–195] (p = 0.03). The indicators MCV, MCH did not reflect the etiology of anemia, MCHC is reduced in all groups. With oral subsidization of 3-valent iron, its level increase in EР: before treatment — 10.65 μmol/l [8.2–12.1], after 2 weeks — 21.95 μmol/l [17.8–23,9] (p = 0.011).Conclusion. Severe and moderate degrees of early anemia of prematurity are diagnosed in the EР and VP groups. Significant deficiency of serum iron was detected in EР at the age of 2 weeks. MCHC less than 33.1% was registered in all gestational periods, it can be the marker of early anemia of prematurity. Iron supplement is required for EР.