The purpose of this study was to determine whether institutionalized older individuals taking proton pump inhibitors (PPI) for more than 12 months were more likely to have vitamin B(12) deficiency than individuals not taking PPI, and whether cyanocobalamin nasal spray would improve their vitamin B(12) status. Participants were long-term care residents aged 60-89 years. PPI users (n = 17) were treated with cyanocobalamin nasal spray for 8 weeks; non-PPI users (n = 19) were not treated but were followed for the same time duration. Serum samples from all subjects were analyzed for vitamin B(12) and serum methylmalonic acid (sMMA) at baseline and the end of the 8-week treatment. There was a significant difference in mean vitamin B(12), sMMA, and frequency of deficiency between control and intervention groups at baseline. After treatment, there was an increase (p = 0.012) in serum vitamin B(12) concentration, and a decrease (p = 0.004) in frequency of deficiency in PPI users. Thus, we found that institutionalized older individuals on PPI for more than 12 months may be more likely to be vitamin B(12) deficient than non-PPI users. Additionally, treatment of PPI users with cyanocobalamin nasal spray for 8 weeks could improve vitamin B(12) status.