Related Experiment Video
Updated: May 19, 2026

A Method of Trigonometric Modelling of Seasonal Variation Demonstrated with Multiple Sclerosis Relapse Data
Published on: December 9, 2015
Overdiagnosed and oversupplemented: the iatrogenic rise of vitamin D toxicity
Aleix B Fabregat-Bolufer1,2, Carlos Martín-Alonso1, Alba Escolà-Rodríguez3
1Biochemistry and Molecular Genetics Department, Biomedical Diagnostic Center (CDB), Hospital Clínic de Barcelona, 08036 Barcelona, Catalonia, Spain.
Abstract:
Spanish pharmacovigilance alerts have highlighted vitamin D overdosing. We retrospectively analysed adult serum 25(OH)D results from a Barcelona tertiary hospital (2020-2025), measured using a VDSCP-certified immunoassay. For results >100 ng/mL (250 nmol/L), concomitant calcium, phosphorus, albumin, alkaline phosphatase and parathyroid hormone were retrieved. Hypercalcemia was defined as albumin-corrected calcium >10.5 mg/dL. Among 185 604 results, annual testing increased by 54.1% and median 25(OH)D rose from 25.3 to 28.6 ng/mL. Very high results more than doubled (31 [0.14%] to 108 [0.31%]; n = 393). Calcium was available in 324/393 results, and hypercalcemia occurred in 14/324 (4.3%). Calcifediol was documented in 183/201 (91.0%) hypervitaminosis D patients with available supplementation data and in 12/14 (85.7%) hypercalcemic cases, often in short-interval dosing regimens. Rapid test growth paralleled a rightward shift and expanding high-concentration tail, supporting evidence-based requesting, clearer intermittent-dosing and supplementation instructions, and selective serum calcium surveillance when 25(OH)D is greatly elevated.
Related Concept Videos
Role of Skin in Vitamin D Synthesis
The solar UV B rays (290-315 nm) are absorbed by the skin, and 7-dehydrocholesterol (provitamin D3) photolyzes it to previtamin D3, which undergoes a rapid transformation to vitamin D3(cholecalciferol).
Vitamins
Hyperthyroidism I: Introduction
Hyperthyroidism II: Pathophysiology
Drug Toxicity: Dose-Dependent Reactions
Drug Toxicity: Risk factors