Introduction and objective:
Vitamin D requirements are not always met by diet and transdermal synthesis. The consequences of its deficiency include bone demineralization, immune system dysfunction, or muscle weakness and pain. Therefore, in many cases, adequate supplementation is recommended. However, an increased awareness of society and prevalence of supplementation frequently lead to its abuse. The aim of the study is to highlight the issue of vitamin D supplementation in society with a particular focus on the causes and consequences of its excessive intake.

Brief description of the state of knowledge:
There is limited information on the prevalence of vitamin D intoxication. However, the available data indicate that the number of cases has increased in recent years. The reason for excess of vitamin D is the intake of very high doses of the vitamin, which may be caused by manufacturing errors and accidental or intentional overdose. It appears to be particularly dangerous when parents give excessive doses to their children. Hypervitaminosis D can lead to serious health consequences, including cardiac arrhythmias, kidney failure, neurological disorders, or even death. During supplementation, it is important to choose licensed preparations, which contain recommended dosages, as overuse of vitamin D not only has no benefit, but can also be harmful.

Summary:
Vitamin D is essential for normal body function. Both its insufficiency and excess should be considered harmful for human health. Only licensed products should be used for supplementation, as their dosage is consistent with the recommended guidelines of health organisations.