Summary: This article focuses on an important problem of the modern healthcare system, which is iron deficiency in elderly patients. It is estimated that iron deficiency anemia affects 10% of people over the age of 65 and even every second person over the age of 85. There are probably many more patients with undiagnosed iron deficiencies of various etiologies. Focusing on geriatric patients, it is necessary to distinguish absolute iron deficiency from functional deficiency, which was also done in this study. The article also presents diagnostic problems, various clinical implications of chronic iron deficiency in the elderly, its most common causes, and therapeutic options. Attention was also paid to specific groups of geriatric patients, such as patients prepared for surgery, cardiological patients, or those suffering from neoplastic diseases. The most important reasons for the deterioration of the quality of life in elderly patients with iron deficiency were discussed. Attempts were made to draw attention to the scale of the problem, which should be not only of interest to hematologists but to doctors and specialists in various fields, including oncologists, surgeons, cardiologists, primary care physicians, laboratory diagnosticians, psychiatrists, psychologists, nutritionists, and many others. The facts presented in this paper prove the need to develop new diagnostic and therapeutic standards responding to the needs of an aging society, which would enable effective treatment and improve the quality of life of elderly patients.