Can a 25(OH)D3 level of 556 ng/mL be asymptomatic? A case report of incorrect supplementation

A BSTRACT Vitamin D3 is crucial for various physiological functions in the body, playing a vital role in the maintenance and regulation of the skeletal, immune, muscular, and nervous systems. Excessive supplementation of Vitamin D3, despite its well-documented health benefits, can lead to toxicity. In severe cases, toxicity manifests as hypercalcemia, hypercalciuria, and multi-organ dysfunction. This report presents a case involving a 58-year-old woman with postmenopausal osteoporosis, who developed markedly elevated serum 25(OH)D3 levels of 556 ng/mL due to uncontrolled cholecalciferol supplementation. Notably, the patient remained asymptomatic, with no abnormalities detected in calcium–phosphate metabolism tests. Vitamin D3 levels normalized spontaneously five months after cessation of supplementation. This case underscores the importance of regular medical oversight when using cholecalciferol, particularly over-the-counter preparations, to monitor calcium–phosphate balance parameters and prevent potential complications.