Background: Concerns have been raised about the quality of the diabetes in-patient service. Nurse prescribing creates an opportunity to improve care for these patients. Aim The aim was to compare in-patients with diabetes who received standard care and an intervention group who had their medicines managed by a Diabetes Specialist Nurse prescriber. Methods: A quasi-experiment was conducted using six wards in a single hospital trust. In-patient care of a convenience sample of patients was evaluated before (n=187) and after (n=265) a Diabetes Specialist Nurse prescriber provided a medicines management intervention. Prospective data were collected to measure insulin and oral hypoglycaemic medication errors and length of stay. Using a smaller sub-sample of participants, sample 2 (n=56), additional data were collected to evaluate the intervention on self-efficacy, patients information needs, and to determine the types of medicines information important to patients. Data collection methods included documentary evidence, modified retrospective case-record review and questionnaires. Findings: Errors were significantly reduced by more than 50% in the intervention group (p < 0.05). The median length of stay was reduced by two days. The total number of errors and length of stay were affected by admission category (p<0.001). In sample 2, self-efficacy scores were increased but the extent to which patients information needs were met was inconclusive. Participants rated similar categories of medicines information as important. Conclusion: A medicines management intervention provided by a Diabetes Specialist Nurse prescriber can have a positive effect on patient safety and quality of care in-patients with diabetes receive. This model of care has important implications in terms of maximising resource use and providing a more flexible and accessible model of service delivery. In order that the contribution of nurse prescribing can be fully realised further evaluation of the intervention is required.