Content of commercially available, single-ingredient vitamin D dietary supplements

With the increased Institute of Medicine recommendation for vitamin D, more consumers are taking vitamin D from over-the-counter or prescription sources. The purpose of this study was to determine the content of commercially available, single-ingredient vitamin D supplements. Eleven commercially available dietary supplement calciferol products were purchased, repackaged, and analyzed for vitamin D content in a laboratory that was blinded to brand or manufacturer of the supplement. Vitamin D was extracted and isolated for analysis by a high-performance liquid chromatography method. Measured vitamin D content was compared with the stated label amount of vitamin D. The percentage of actual vitamin D contained in the supplements ranged from 82% and 119% of the stated label amount. Despite anecdotal reports of products with substantial content deviations from the labeled amount, no remarkable departures from labeled content were found in this set of vitamin D preparations.