Reviewing the cases of 548 patients over the age of 60 who were admitted at South Glasgow University Hospital during a four-year period, the researchers found that 97.8 per cent had vitamin D levels below normal.
In around a quarter of the group studied, levels were so low that they were "effectively unrecordable", said the authors in the online issue of Current Medical Research and Opinion (DOI: 10.1185/030079905X59148).
Vitamin D currently only makes up 4 per cent of all vitamin sales and lags well behind calcium in terms of bone health supplements. But increasing evidence underlines its importance in protecting against fractures.
In a second prospective study phase, the researchers looked at vitamin D levels among the first 50 patients admitted to the hospital with an osteoporosis fracture after November 2004.
More than 80 per cent had vitamin D levels below 70 nmol/L and 72 per cent had vitamin D levels below 50 nmol/L.
"Although numbers were too small to justify extensive subgroup analyses, the mean vitamin D level in the 13 patients with hip fracture was lower than in the 37 with non-hip fractures," said the researchers.
They conclude: "It may be that vitamin D represents a correctable risk factor for fragility fracture in the elderly, possibly specifically for the hip."