Background Insulin is a high-risk medicine, associated with hospital medication errors. Pharmacists play an important role in the monitoring of patients on insulin. Objective To analyse interventions made by hospital pharmacists that were associated with insulin prescribing for inpatients with diabetes. Method Retrospective audit of pharmacist interventions for adult inpatients for an 8-month period, 1 June 2019–31 January 2020. Pharmacist interventions recorded in the electronic medication management system by inpatient unit and dedicated high-risk medicine pharmacists were extracted, screened, and analysed. Results Of 3975 pharmacist interventions 3356 (84.43%) were recorded by high-risk medicine pharmacists and 619 (15.57%) by inpatient unit pharmacists. July and August 2019 had the highest numbers of interventions with 628 and 643 (15.80 and 16.18%) respectively. Most of the interventions, namely 3410 (85.79%) were classified as medicine optimisation interventions and 565 (14.21%) as prescribing errors. In the medicine optimisation intervention category, 2985 (75.09%) were due to insulin not charted for ongoing administration. Conclusion This study provides insights into pharmacist interventions for inpatients on insulin, showing that high-risk medicine pharmacists recorded most interventions. The classification of the insulin interventions into medicine optimisation and prescribing errors provides useful information for the training of prescribers in insulin management.