Annals of Clinical Biochemistry > Volume 45, Number 1 > Pp. 106-110

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kimball, S. Articles by Vieth, R. Search for Related Content PubMed PubMed Citation Social Bookmarking                      What's this?

Case Report

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

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}utoronto.ca

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 biochemical responses confirmed that an increase in urinary calcium:creatinine ratio precedes hypercalcaemia as serum 25(OH)D concentrations rise.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?