INTRODUCTION: Oxygen guidelines recommend a target saturation range (SpO METHODS: We audited SpO RESULTS: Of 1,045,958 observations from patients with an oxygen prescription, 107,724 (10.3 %) had a target range of 88-92 % (at risk of hypercapnia). 26,668 of these observations (24.8 %) involved oxygen use. 89.6 % of the SpO SUMMARY: We found that excessive oxygen administration was much commoner than insufficient oxygen therapy for hospital patients at risk of hypercapnia. Excessive oxygen use implies an increased risk of harm to these patients, increased cost, and potentially delayed discharges.