Vitamin D deficiency is one of the important risk factors for the development of osteoporosis and fractures. The high prevalence of hypovitaminosis in elderly people in old age pnesioners homes was proved in several investigations, similarly as the favourable effect of vitamin D (800 IU/day) and calcium supplementation on a decline of fracture risk. Risk factors of hypovitaminosis such as an inadequately varied diet; low exposure to sunlight, chronic liver and kidney disease and treatment affecting the metabolism and clearance of vitamin D are very frequent in elderly patients hospitalized in medical departments. In the submitted trial the authors assessed in a group of 38 patients, mean age 70 years, hospitalized at the medical department at the end of the winter period the vitamin D3 serum level. They found a significant reduction of the concentration of 1.25 hydroxyvitamin D3 (p < 0.01) in the investigated group. The results of the trial, along with data in the literature on the high prevalence of hypovitaminosis D in the European population, indicate the need to introduce this simple cheap and safe therapeutic modality into routine practice.