BackgroundManaging medications inappropriately when patients have oral intake restrictions can cause patient harm. This study evaluated the impact of a medication policy separating fasting from nil by mouth with respect to giving oral medications in patients fasting before a diagnostic or interventional procedure.MethodsThe policy stipulated that ‘fasting’ means oral medications should be given with a sip of water up to 1 hour before a procedure, unless there is a clinical reason to withhold, while ‘nil by mouth’ means nothing to be given orally, including medications.The policy was implemented in Surgical areas in February 2015 and Medical areas in March 2015 at a tertiary referral hospital in Melbourne, Australia, and included bedside signs, clinical champions and education sessions.The study was conducted in 2020. Admission and medication records were matched for non-elective procedure patients from January 2014 to May 2016. The monthly proportion of doses omitted inappropriately and overall omissions pre/post-policy implementation were compared using segmented regression.ResultsPre-implementation, the proportion of doses withheld inappropriately and total omissions in medical areas were 18.1% and 28.0%, respectively. Post-implementation, an absolute reduction of 13.4% (95% CI 9.0% to 17.7%) and 11.1% (95% CI 2.6% to 19.6%), respectively, was seen. Post-implementation linear trend showed a 0.3% (95% CI 0.0% to 0.6%) increase in inappropriate omissions but not overall omissions.In Surgical areas, pre-implementation proportions for inappropriate and overall omissions were lower than Medical areas’. Post-implementation, there was an absolute decrease in doses withheld inappropriately (8.3%, 95% CI 0.8% to 15.7%, from 11.9% pre-implementation) but not total omissions.ConclusionsDistinguishing fasting from nil by mouth appeared to provide clarity for some staff: a reduction in inappropriate omissions was seen post-implementation. Although the small increase in post-implementation linear trend for inappropriate omissions in Medical areas suggests sustainability issues, total omissions were sustained. The policy’s concepts require verification beyond our institution.