Self-prescribed high-dose vitamin D3: effects on biochemical parameters in two men

Ann Clin Biochem 2008;45:106-110
© 2008 Association for Clinical Biochemistry


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Case Report

Samantha Kimball 1 2  and
Reinhold Vieth 1 2 3

1 Department of Nutritional Sciences, University of Toronto, Toronto, Canada M5S 3E2;
2 Department of Pathology and Laboratory Medicine, Mt Sinai Hospital, Toronto, Canada M5G 1X5;
3 Department of Laboratory Medicine and Pathology, University of Toronto, Toronto, Canada M5S 3E2

Corresponding author: Dr Samantha Kimball, Department of Pathology and Laboratory Medicine, Mt Sinai Hospital, Toronto, Canada M5T 3L9. Email: samantha.kimball{at}

The lowest observed adverse effect level for vitamin D, said to cause hypercalcaemia in normal adults, is officially 95 µg/day. Serum 25-hydroxyvitamin D (25[OH]D) concentrations associated with hypervitaminosis D remain undefined. Reported 25(OH)D concentrations resulting from prolonged excessive vitamin D3 intakes have exceeded 700 nmol/L. We report self-prescribed high dose of vitamin D3 over 5–6 years by two men. Subject 1 had been taking 100 µg/day for 3 years followed by 3 years of 200 µg/day. Serum 25(OH)D concentrations averaged 130 nmol/L while taking 100 µg/day of vitamin D3. While taking 200 µg/day of vitamin D3, mean serum 25(OH)D concentrations were 260 nmol/L with no hypercalcaemia or hypercalcuria over the 6 years of vitamin D3 intake. Subject 2 was a 39-year-old man diagnosed with multiple sclerosis. He initiated his own dose-escalation schedule. His vitamin D3 intake increased from 200 to 2200 µg/day over 4 years. The first evidence of a potential adverse effect was that urinary calcium:creatinine ratios showed an increasing trend, which preceded serum calcium concentrations above the reference range (2.2–2.6 mmol/L). His serum 25(OH)D concentration was 1126 nmol/L when total serum calcium reached 2.63 mmol/L. He stopped vitamin D3 supplementation at this point. Two months later, all biochemistry values were within reference ranges; serum 25(OH)D concentrations fell by about one-half, to 656 nmol/L. These results help to clarify the human response to higher intakes of vitamin D3. Close monitoring of biochemicalresponses confirmed that an increase in urinary calcium:creatinineratio precedes hypercalcaemia as serum 25(OH)D concentrationsrise.

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