Summary: Iron (Fe) is a microelement necessary for life. A 70 kg man has approximately 3.5 g of Fe (65–75% contains hemoglobin, 10-20% myoglobin, cytochromes, etc., and the rest is stored by the liver, macrophages and bone marrow). We consume 15–20 mg of Fe in our diet (of which 1–2 mg/day is absorbed). They balance absorption loss with shed enterocytes and colonocytes, and in women, with menstruation. Fe is absorbed only in the duodenum and its damage usually leads to sideropenic anemia. Fe assimilation is regulated by the crypt and hepcidin-related mechanisms. The requirement for Fe in infants is 1–15 mg/kg body weight/day, and in premature babies – 2–15 mg/ kg body weight/day, from 1 to 10 years of age 10 mg/day, and from 10 years of age – 12–15 mg/day. Menstruating women need about 15 mg/day, and pregnant women even 30 mg/ day. Meeting the demand is difficult due to the low content of Fe in the diet and its varying bioavailability depending on its form (heme, Fe2+, Fe3+). Fe deficiency affects approximately 1.5–1.8 billion people around the world. Treatment of Fe deficiency and sideropenic anemia usually requires the use of oral Fe preparations. Most of them require high dosages, blacken teeth, cause nausea, abdominal pain and constipation, and unabsorbed Fe leads to dysbiosis. Damage to the duodenal villi (e.g. in celiac disease) may dramatically reduce the effects of oral therapy. To bypass these barriers, liposomal technology was used, creating, among others, sucrosomal iron. It is absorbed not only in the duodenum and regardless of the concentration of hepcidin. Sucrosomal Fe penetrates the enterocyte, between enterocytes and additionally through M cells, and therefore requires four times lower doses and causes side effects much less frequently (in less than 9% of treated patients). Another method that can overcome the barriers related to oral Fe supply is the use of Lactobacillus plantarum 299v.