Laboratory trend in vitamin D status in Ireland: Dual concerns about low and high 25OHD

Serum 25-hydroxyvitamin D (25OHD) is the pre-eminent estimate of vitamin D status that we have been measuring in a hospital laboratory setting since the 1970s. We previously evaluated the trend in 25OHD results in our laboratory from 1993 to 2013. Using a time series analysis of monthly average 25OHD results the trend was modelled, and this was used to forecast monthly average 25OHD from 2014 to 2016. In this study, all 25OHD results from 2014 to 2016 were retrieved (n = 67,922) and trimmed to 40,307 results after duplicates were excluded. The average monthly actual 25OHD was almost identical to the average monthly forecast 25OHD (p = 0.028) with a strong correlation between the actual 25OHD and forecast 25OHD (r = 0.69, p < 0.001). This upward trend is attributed to higher oral intake of vitamin D. We have a dual concern: policies to prevent hypovitaminosis D must be offset by strategies to avert hypervitaminosis D.