Summary: Anemia is defined as a reduction in the total number of red blood cells or a decrease in hemoglobin concentration below the established reference range for age and sex. Microcytic anemia secondary to iron deficiency represents the most common form of anemia in the pediatric population. The etiology of iron deficiency includes increased physiological demand in the context of insufficient dietary intake, impaired gastrointestinal absorption, chronic blood loss, or nutritional deficiencies. The standard approach to routine laboratory diagnostics includes a panel of three tests: complete blood count with peripheral blood smear, reticulocyte count, and serum ferritin concentration. A decreased ferritin concentration (below 12 μg/L in children under 5 years of age; below 15 μg/L in children over 5 years) is indicative of depleted iron stores. Indications for iron supplementation as prophylaxis are categorized into absolute and relative indications. The recommended prophylactic dosage is 2 mg of elemental iron per kilogram of body weight per day. Treatment efficacy is typically assessed by an increase in reticulocyte count exceeding 2% and a rise in hemoglobin concentration by at least 1 g/dL within 10–14 days of initiating iron therapy. In cases where normalization of erythrocyte parameters does not occur within 2–3 weeks of treatment, the initial diagnosis should be reassessed and further diagnostic workup undertaken. Detailed diagnostics of iron status parameters is not recommended in asymptomatic children who do not belong to a recognized risk group.