Background and ObjectivesA plasma transfusion dose should be weight‐based (10–20 mL/kg), which equates to three to four units in an average‐sized adult; therefore, the transfusion of single units under most circumstances is sub‐therapeutic.Materials and MethodsThis retrospective observational study examined the prevalence of single‐unit plasma transfusion in adults within a 12‐hospital system from 1 January 2018, to 31 December 2019.ResultsDuring the study period, 5791 patients received plasma transfusions. The overall prevalence of single‐unit plasma was 17.1% for 988 patients. The majority, 3047 (52.6%), occurred at one hospital, 2132 (36.9%) among five hospitals and 612 (10.7%) at the remaining six hospitals. Cardiac and gastrointestinal (GI)/transplant transfused 2707 (46.8%), combined respiratory, neurological, orthopaedic and congenital/dermatology/other comprised 2133 (36.9%) of the six hospitals that transfused less than 200 patients, four (66.7%) transfused single units above the overall prevalence.ConclusionIn this hospital system, more than one in six patients received a transfusion of a single plasma unit. Six of the 12 hospitals had 89.5% of the patients who were transfused plasma. Six service lines transfused 83.7% of all patients receiving plasma. Hospitals that infrequently transfused plasma were more likely to under‐dose.