Introduction  Many studies have demonstrated the prevalence of vitamin D insufficiency in the older population.

Objective  This study sought to determine whether supplementation with intramuscular vitamin D improved 25OH vitamin D levels significantly.

Subjects  Ninety female inpatients aged over 65 years were assigned to receive 300,000 IU of intramuscular vitamin D3 (cholecalciferol) or no intervention.

Methods  Baseline 25OH vitamin D and intact parathyroid hormone (iPTH) levels were taken and repeated 3 months after supplementation.

Results  Patients who received treatment showed a significant improvement in 25OH vitamin D levels, from 25.5 to 81 nmol/L with 11% remaining deficient. No patient became hypercalcaemic after treatment.

Conclusions  Vitamin D deficiency is common throughout all age groups in the Irish population and particularly the older female population who have increased risk of osteoporosis and fractures. Intramuscular vitamin D significantly improves 25OH vitamin D levels compared to no treatment and may combat non-compliance with oral medication.