Background: Taking into account the multi-directional beneficial effects of vitamin D₃ and its widespread deficiency, regular supplementation is recommended. However, more and more attention is being paid to the risk of overdose with supplemented vitamin D₃ and the associated serious health consequences. Material and Methods: The concentration of 25-hydroxyvitamin D (25(OH)D) is a routine test recommended upon admission to the Geriatrics Clinic of Wroclaw Medical University. The aim of the study was to analyze the results from January 2018 to June 2023. Additionally, information on the reported symptoms, gender and age of people with an increased level of vitamin D₃ was collected. Results: Analyzing a group of 1400 patients, it was noted that within 5 years, vitamin D₃ concentrations exceeding the recommended level were recorded in 7 patients, including 3 with toxic levels. All abnormal results occurred in women. The most frequently reported symptoms included general weakness, lower limbs and joint pain, sleep disorders, low mood. People with toxic concentrations reported dizziness. In seniors there is a gradual increase in vitamin D concentration and its deficiency is less common. Higher concentrations were recorded in the group of older seniors, and concentrations considered toxic occur in the population >74 years of age. Supplements and drugs with vitamin D are most often used without consulting a doctor, without determining the appropriate dose, or without assessing the concentration of 25(OH)D in the serum. Conclusions: To prevent vitamin D deficiency in seniors, doses >4000 IU daily are not recommended. It is advisable to check all medications and supplements taken at each doctor’s visit in terms of duplicating treatment with vitamin D. It is advisable to assess the status of vitamin D supply the concentration of 25(OH)D in order to select the appropriate dose. Assessment of 1,25-dihydroxyvitamin D concentration is recommended in cases of vitamin D toxicity. Med Pr Work Health Saf. 2024;75(3):286–292