Anemia is a group of diseases characterized by a decrease in the number of circulating erythrocytes and/or hemoglobin per unit of blood volume below normal for a given age and gender. Chronic iron deficiency anemia (IDA) occurs more often (80–95% of all anemias) in real clinical practice. IDA is often found in the practice of a gastroenterologist and in patients of surgical departments. This review discusses the most significant aspects of the diagnosis and treatment of IDA in the practice of a gastroenterologist and surgeon. Parenteral iron preparations are indicated in cases where there are contraindications to the use of oral preparations or they are ineffective. In surgical practice (if it is necessary to quickly replenish iron in the body) and in gastroenterology (peptic ulcer and duodenal ulcer, a history of surgical interventions in the gastrointestinal tract, Crohn's disease, ulcerative colitis, malabsorption syndrome), parenteral iron preparations are considered as drugs of choice. The results of numerous international and Russian studies indicate the efficacy and safety of iron (III) hydroxide oligoisomaltosate as the drug of choice for the treatment of absolute or functional iron deficiency states in the absence of the effectiveness of oral iron preparations and, if necessary, rapid iron replacement.