One of the main fat-soluble vitamins is vitamin D, whose primary function is the regulation of calcium-phosphate metabolism and mineralization of bone tissue. Vitamin D occurs in two forms: vitamin D2 (ergocalciferol) – found in plants and fungi (mainly yeasts) and vitamin D3 (cholecalciferol) – produced in animals. Hypovitaminosis of vitamin D leads to metabolic bone diseases in children and adults and can also affect the incidence of many chronic diseases such as: multiple sclerosis, diabetes, rheumatoid arthritis, bronchial asthma, cancer, atherosclerosis, coronary artery disease and heart failure. The aim of the current study was to assess the content of vitamin D in dietary supplements available in pharmacies and supermarkets in the EU. The evaluation involved analysing the ratio of vitamin D content in supplements in relation to the typical demand of the organism. This study assessed 15 popular over-the-counter dietary supplements in the form of tablets, capsules, lozenges and lollipops for children as well as in the form of effervescent tablets. On the basis of the labels on the packaging, the vitamin D content of the supplements was assessed in relation to the dietary demands of the body. Self-administration of over-the-counter multivitamin supplements is not an optimal way to increase vitamin D levels. It is recommended, therefore, that individuals requiring vitamin D supplementation seek specialist medical advice to optimal treatment strategies.