Background: Thiamine supplementation is recommended for patients with alcohol use disorder (AUD). The authors hypothesize that critically ill patients with AUD are commonly not given thiamine supplementation. Objective: To describe thiamine supplementation incidence in patients with AUD and various critical illnesses (alcohol withdrawal, septic shock, traumatic brain injury [TBI], and diabetic ketoacidosis [DKA]) in the United States. Design: Retrospective observational study. Setting: Cerner Health Facts database. Patients: Adult patients with a diagnosis of AUD who were admitted to the intensive care unit with alcohol withdrawal, septic shock, TBI, or DKA between 2010 and 2017. Measurements: Incidence and predicted probability of thiamine supplementation in alcohol withdrawal and other critical illnesses. Results: The study included 14 998 patients with AUD. Mean age was 52.2 years, 77% of participants were male, and in-hospital mortality was 9%. Overall, 7689 patients (51%) received thiamine supplementation. The incidence of thiamine supplementation was 59% for alcohol withdrawal, 26% for septic shock, 41% for TBI, and 24% for DKA. Most of those receiving thiamine (n= 3957 [52%]) received it within 12 hours of presentation in the emergency department. The predominant route of thiamine administration was enteral (n = 3119 [41%]). Limitation: Specific dosing and duration were not completely captured. Conclusion: Thiamine supplementation was not provided to almost half of all patients with AUD, raising a quality-of-care issue for this cohort. Supplementation was numerically less frequent in patients with septic shock, DKA, or TBI than in those with alcohol withdrawal. These data will be important for the design of quality improvement studies in critically ill patients with AUD.