Research Objectives Assess utilization and impact of a specialized oral nutrition supplement (ONS) containing arginine, glutamine, and hydroxymethylbutyrate (HMB) on wound healing. Design Retrospective analysis comparing treatment group (51 patients, 161 wounds) receiving standard care plus a specialized ONS for ≥14 days and comparison group (136 patients, 263 wounds) receiving standard care. Between group differences evaluated using t-tests and mixed models with inverse probability weighting. Setting Inpatient rehabilitation hospital. Participants 187 adult patients admitted between 1/2018-12/2019 with ≥1 measured wound and ≥2 wound care nurse assessments. Interventions Specialized oral nutrition supplement administered for 14 days. Main Outcome Measures Wound healing was measured in weekly intervals by decrease in wound surface area (superficial) or volume (non-superficial) in past 1 week. Results While no age differences were reported between groups (50.9 vs 51.0 years, p=1.0), the treatment group had a higher percentage of male patients (90.2% vs 69.9%, p<0.01). Treatment group patients had more wounds (3.3 vs 2.0, p<0.01), lower functional independence measure scores (35.7 vs 40.3, p=0.082), and a higher case mix index (2.3 vs. 2.0, p=0.008) at baseline. Average inpatient stay (44. 8 vs 39.9 days, p=0.36) and wound area at baseline (22.0 vs 13.1 cm2, p=0.18) were higher, but not statistically different, in the treatment group. Treatment group wounds significantly decreased in area (61.0% vs 34.6%, p=0.01) compared to comparison group wounds. The odds of a decrease in wound size were higher in the treatment versus comparison group (OR = 24.1, p<0.01). Conclusions Patients receiving specialized ONS had more wounds and higher acuity level than those in the comparison group but had a significant reduction in wound size. There are several limitations in this retrospective study, including baseline functional and wound size differences. However, these findings support the benefits of specialized ONS in improving wound healing for patients with pre-existing wounds. Author(s) Disclosures KW Kerr, S Sulo and JL Nelson are Abbott employees and stockholders. Study financially supported by Abbott. Assess utilization and impact of a specialized oral nutrition supplement (ONS) containing arginine, glutamine, and hydroxymethylbutyrate (HMB) on wound healing. Retrospective analysis comparing treatment group (51 patients, 161 wounds) receiving standard care plus a specialized ONS for ≥14 days and comparison group (136 patients, 263 wounds) receiving standard care. Between group differences evaluated using t-tests and mixed models with inverse probability weighting. Inpatient rehabilitation hospital. 187 adult patients admitted between 1/2018-12/2019 with ≥1 measured wound and ≥2 wound care nurse assessments. Specialized oral nutrition supplement administered for 14 days. Wound healing was measured in weekly intervals by decrease in wound surface area (superficial) or volume (non-superficial) in past 1 week. While no age differences were reported between groups (50.9 vs 51.0 years, p=1.0), the treatment group had a higher percentage of male patients (90.2% vs 69.9%, p<0.01). Treatment group patients had more wounds (3.3 vs 2.0, p<0.01), lower functional independence measure scores (35.7 vs 40.3, p=0.082), and a higher case mix index (2.3 vs. 2.0, p=0.008) at baseline. Average inpatient stay (44. 8 vs 39.9 days, p=0.36) and wound area at baseline (22.0 vs 13.1 cm2, p=0.18) were higher, but not statistically different, in the treatment group. Treatment group wounds significantly decreased in area (61.0% vs 34.6%, p=0.01) compared to comparison group wounds. The odds of a decrease in wound size were higher in the treatment versus comparison group (OR = 24.1, p<0.01). Patients receiving specialized ONS had more wounds and higher acuity level than those in the comparison group but had a significant reduction in wound size. There are several limitations in this retrospective study, including baseline functional and wound size differences. However, these findings support the benefits of specialized ONS in improving wound healing for patients with pre-existing wounds.