Background: Oxygen is a widely used drug in the hospital setting. However, international audits suggest that oxygen administration practices are often not compliant with prescribed standards. This can place patients at risk and cause serious adverse events. Aim: To analyse data related to recent practices of oxygen prescription and administration at Royal Perth Hospital (RPH), Western Australia. The results of this audit aim to guide further research on possible interventional studies implementing key solutions. Methods: All patients who received care in the Acute Medical Unit at RPH between 1 September and 14 September 2015 were included in this audit. Patients who were given supplemental oxygen during their admission were selected for further review of records. Appropriate medically indicated target oxygen saturations for each patient were judged under consultation with a respiratory specialist. Results: A total of 65 patients received oxygen supplementation within the study period; 36 of these patients (55.4%) had target oxygen saturations prescribed by doctors, and 25% of the prescribed targets were judged to be inappropriate. In total, 49 patients (75.4%) were exposed to a potential risk from oxygen therapy due to prescription error and/or delivery error. A real risk was identified in 19 patients (29.2%) as they received oxygen at levels outside their appropriate medically indicated target range. Conclusion: The current practices of oxygen prescription and administration within RPH are suboptimal. Patients are placed at risk of oxygen toxicity due to deviation from oxygen prescription guidelines.