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Lab Med. 2018 Mar 21;49(2):123-129. doi: 10.1093/labmed/lmx077.

Vitamin D Toxicity: A 16-Year Retrospective Study at an Academic Medical Center.

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Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA.
Divisions of Pediatric Endocrinology, University of Iowa Stead Family Children's Hospital, Iowa City, IA.
Divisions of Pediatric Nephrology, Dialysis, and Transplantation, University of Iowa Stead Family Children's Hospital, Iowa City, IA.



Interest in vitamin D has increased during the past 2 decades, with a corresponding increase in laboratory testing of 25-hydroxyvitamin D [25(OH)D]. The vast majority of specimens tested display normal or deficient levels of 25(OH)D; concentrations rarely fall in the potentially toxic range.


We performed a retrospective investigation of elevated 25(OH)D levels during a 16-year period at the University of Iowa Hospitals and Clinics (UIHC), a 734-bed tertiary-/quaternary-care academic medical center in the midwestern United States. Detailed medical-record review was performed for patients with serum/plasma 25(OH)D concentrations higher than 120 ng per mL.


A total of 127,932 serum/plasma 25(OH)D measurements were performed on 73,779 unique patients. Of these patients, 780 (1.05%) had results that exceeded 80 ng per mL and 89 patients (0.12%) had results that exceeded 120 ng per mL. Only 4 patients showed symptoms of vitamin D toxicity. Three of these cases involved inadvertent misdosing of liquid formulations.


Symptomatic vitamin D toxicity is uncommon, and elevated levels of 25(OH)D do not strongly correlate with clinical symptoms or total serum/plasma calcium levels. Our study highlights the potential risks of the liquid formulation of vitamin D.

[Indexed for MEDLINE]

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