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

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.