Aim: Recent data has shown that vitamin D increases insulin sensitivity; however, there is little evidence about the effects of this treatment on elderly people with impaired fasting glucose. The aim of the present study was to investigate the effect of vitamin D treatment on insulin sensitivity and metabolic parameters in elderly people with impaired fasting glucose. Methods: A total of 28 elderly patients were enrolled into the vitamin D treatment group. The control group included 23 age-, sex- and body mass index-matched elderly participants. The vitamin D treatment group was treated with vitamin D3 according to serum concentrations of 25(OH)D. Results: With supplementation, 96.0% of patients achieved a mean serum 25(OH)D concentration of 123.2 +/- 59.9 nmol/L. After 4.7 +/- 2.5 months of treatment, there was a significant decrease in homeostasis model assessment of insulin resistance, insulin and glucose concentrations in the vitamin D treatment group (P = 0.007, P = 0.007, P = 0.037, respectively). Vitamin D treatment significantly increased high-density lipoprotein cholesterol (P = 0.037), but did not cause statistically significant differences in other lipid parameters. Conclusion: We found that vitamin D treatment might modify insulin sensitivity in the elderly with impaired fasting glucose. Geriatr Gerontol Int 2012; 12: 454460.