An Outbreak of Vitamin D Toxicity in a Family: Report of 3 Cases From Unregulated Fortification

Vitamin D toxicity is a rare but potentially life-threatening cause of PTH-independent hypercalcemia. While most cases result from inappropriate supplement use, food-related exposures are increasingly recognized. We report a cluster of 3 adults from the same household who presented within 3 days with severe hypercalcemia and acute kidney injury. All had markedly elevated 25-hydroxyvitamin D, suppressed intact PTH, and a shared history of consuming locally sourced, unpackaged cooking oil. Liquid chromatography-tandem mass spectrometry analysis of the retained oil confirmed toxic vitamin D₃ contamination at 1286 μg/mL (SI: ∼3.34 × 10⁶ nmol/L). Treatment included IV fluids, calcitonin, and denosumab; 1 required dialysis. All recovered fully. This case series highlights the need to consider dietary sources in familial hypercalcemia and underscores the importance of regulating food fortification and edible product safety.