How much is too much? Two contrasting cases of excessive vitamin D supplementation

Area of Science:

• Endocrinology
• Clinical Pharmacology
• Nutritional Science

Background:

• Hypervitaminosis D is a condition of excessive vitamin D levels.
• This report details two distinct cases of vitamin D toxicity.

Observation:

• Patient 1, a 75-year-old man, experienced symptomatic hypercalcemia, cardiac injury, and elevated vitamin D (243 ng/ml) from daily ergocalciferol (vitamin D2) and calcium-citrate for one year.
• Patient 2, a 60-year-old woman, had very high vitamin D (479 ng/ml) from daily cholecalciferol (vitamin D3) for over 10 months but remained asymptomatic.

Findings:

• These cases highlight the wide variability in individual responses to prolonged supraphysiologic vitamin D concentrations.
• Defining a specific toxic threshold for vitamin D is challenging due to differing patient outcomes.

Implications:

• Patient pharmacodynamics, or how an individual's body processes a drug, significantly influence the clinical effects of high-dose vitamin D therapy.
• Clinical management of vitamin D supplementation requires consideration of individual patient variability.