Annual vitamin D testing increased 54.1% and very high results more than doubled over 5 years at a Barcelona tertiary hospital, with hypercalcemia occurring in 4.3% of cases with very elevated 25(OH)D, predominantly associated with calcifediol supplementation.
Annual vitamin D testing volume increased substantially over the study period at a Barcelona tertiary hospital.
Median serum 25(OH)D levels rose over the study period, indicating a rightward population-level shift in vitamin D status.
The number of very high vitamin D results (>100 ng/mL) more than doubled during the study period.
Hypercalcemia occurred in 4.3% of cases where calcium measurements were available alongside very elevated vitamin D levels.
Calcifediol supplementation was the predominant supplement associated with hypervitaminosis D and hypercalcemia cases.
Spanish pharmacovigilance alerts have highlighted vitamin D overdosing as a recognized safety concern.
The authors recommend selective serum calcium surveillance when 25(OH)D is greatly elevated.
This research suggests that vitamin D testing and supplementation have increased substantially in recent years, with potentially harmful consequences for some patients. Analyzing over 185,000 vitamin D blood test results from a large hospital in Barcelona between 2020 and 2025, the researchers found that the number of tests performed grew by more than half, average vitamin D levels in patients rose, and the number of people with dangerously high vitamin D levels more than doubled. Among those with very high vitamin D levels, about 1 in 23 also had high blood calcium (hypercalcemia), a condition that can cause symptoms such as fatigue, nausea, kidney problems, and confusion. The research also suggests that a specific form of vitamin D supplement called calcifediol was involved in the vast majority of cases with very high vitamin D levels and in most of the cases where high blood calcium developed. Calcifediol is a more potent and faster-acting form of vitamin D than the more commonly known cholecalciferol (vitamin D3), and it appears to have been frequently prescribed in dosing schedules that may not have provided enough time between doses, potentially leading to accumulation in the body. The practical implication of this research is that vitamin D testing may be occurring more often than is medically necessary, and that supplementation — particularly with calcifediol — may sometimes be prescribed without sufficient caution about dosing intervals or follow-up monitoring. The authors suggest that clearer prescribing guidelines, more selective use of vitamin D testing, and monitoring of blood calcium levels in patients with very high vitamin D results could help reduce the risk of toxicity.
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Upload Your LabsFabregat-Bolufer A, Martín-Alonso C, Escolà-Rodríguez A, Morales-Ruiz M. (2026). Overdiagnosed and oversupplemented: the iatrogenic rise of vitamin D toxicity.. European journal of endocrinology. https://doi.org/10.1093/ejendo/lvag088