Background Patients with opioid use disorder (OUD) who are hospitalized for serious infections requiring prolonged intravenous antibiotics may face barriers to discharge, which could prolong hospital length of stay (LOS) and increase financial burden. We investigated differences in LOS, discharge disposition, and charges between hospitalizations for serious infections in patients with and without OUD. Methods and findings We utilized the 2016 National Inpatient Sample—a nationally representative database of all discharges from US acute care hospitals. The population of interest was all hospitalizations for infective endocarditis, epidural abscess, septic arthritis, or osteomyelitis. The exposure was OUD, and the primary outcome was LOS until discharge, assessed by using a competing risks analysis to estimate adjusted hazard ratios (aHRs). Adjusted odds ratio (aOR) of discharge disposition and adjusted differences in hospital charges were also reported. Of 95,470 estimated hospitalizations for serious infections (infective endocarditis, epidural abscess, septic arthritis, and osteomyelitis), the mean age was 49 years and 35% were female. 46% had Medicare (government-based insurance coverage for people age 65+ years), and 70% were non-Hispanic white. After adjustment for potential confounders, OUD was associated with a lower probability of discharge at any given LOS (aHR 0.61; 95% CI 0.59–0.63; p < 0.001). OUD was also associated with lower odds of discharge to home (aOR 0.38; 95% CI 0.33–0.43; p < 0.001) and higher odds of discharge to a post-acute care facility (aOR 1.85; 95% CI 1.57–2.17; p < 0.001) or patient-directed discharge (also referred to as “discharge against medical advice”) (aOR 3.47; 95% CI 2.80–4.29; p < 0.001). There was no significant difference in average total hospital charges, though daily hospital charges were significantly lower for patients with OUD. Limitations include the potential for unmeasured confounders and the use of billing codes to identify cohorts. Conclusions Our findings suggest that among hospitalizations for some serious infections, those involving patients with OUD were associated with longer LOS, higher odds of discharge to post-acute care facilities or patient-directed discharge, and similar total hospital charges, despite lower daily charges. These findings highlight opportunities to improve care for patients with OUD hospitalized with serious infections, and to reduce the growing associated costs., In a study of nationally representative hospital discharges in the US included in the 2016 National Inpatient Sample database, June-Ho Kim and colleagues identify associations between opioid use disorder and factors related to hospitalization for the treatment of serious bacterial infections., Author summary Why was this study done? There has been an increase in hospitalizations in the United States for serious infections among patients with opioid use disorder. These infections typically require several weeks of intravenous antibiotics, which can eventually be administered at home or at facilities outside of the hospital if the patient has no other inpatient needs. However, patients with opioid use disorder are often kept in the hospital to finish their treatment, which could have significant financial costs, use hospital resources, and cause patient harm. We conducted this study in order to understand differences in length of hospital stay, type of hospital discharge, and related financial charges between patients with and without opioid use disorder in the US. What did the researchers do and find? We analyzed a cross-sectional dataset representative of all hospitalizations for serious infections in the US during 2016 and compared length of hospital stay, type of hospital discharge, and financial charges. From 95,470 estimated hospitalizations, patients with opioid use disorder stayed an average of 4 days longer in the hospital compared to those without the disorder, with a 39% lower likelihood of discharge from the hospital at any given length of stay. Patients with opioid use disorder were less likely to be discharged home and more likely to be sent to a post-acute care facility or to self-discharge. Although daily hospital charges were lower for patients with opioid use, charges for the total hospitalization were similar given the longer stays. What do these findings mean? These disparities in hospital stays and destinations after discharge suggest that people with opioid use disorder may lack post-discharge options such as skilled nursing facilities or home care for antibiotic infusions and thus remain in the hospital longer than their counterparts without opioid use disorder. Consideration should be given to expanding discharge options for people with opioid use disorder to reduce costly hospital stays and provide equitable care for serious infections.