Background: Vitamin D intoxication (VDI) is a rare cause of kidney injury, but it can have fatal consequences. We would like to present two cases of patients in whom high doses of vitamin D intake led to significant health problems. Case Presentation: The first case is a 68-year-old woman taking approximately 20,000 IU of vitamin D daily. On admission, laboratory tests showed elevated renal function parameters, hypercalcemia, and elevated serum vitamin D concentration. The second case was a 71-year-old man intoxicated with vitamin D two and a half years earlier, as a consequence the patient was included in the chronic hemodialysis program. Because of a potentially reversible cause of kidney disease – signs of tubulointerstitial nephritis and persistent high serum vitamin D concentration, attempt of hemodialysis withdrawal was made, steroid therapy was administered, without expected effect. Discussion: A persistent problem is supplementing with high doses of vitamin D without medical supervision. It is estimated that a significant number of people in the U.S. population takes more than 4,000 IU of vitamin D per day. These are the doses that have been linked to numerous health benefits by unverified sources, even though in recent years scientific studies have been able to refute some of these claims. Based on the two cases we have presented, we want to emphasize how serious the consequences of vitamin D intoxication can be. Conclusions: Vitamin D intoxication may cause acute kidney injury, and in some cases may lead to end-stage renal failure and require renal replacement therapy.