OBJECTIVES: The objective of this study was to compare costs and resource utilization of patients experiencing post-admission dehydration (PAD) to those who do not experience PAD. METHODS: All adult inpatient discharges excluding those with suspected dehydration present on admission (ICD-9-CM codes for dehydration: 276.0, 276.1, 276.5X present on admission) were identified from the Premier database(CY2011). Patients with missing information on important variables were excluded. PAD patients were identified using ICD-9-CM codes. PAD and no PAD(NPAD) groups were matched on propensity score adjusting for demographics (age, gender, race, medical, elective patients), patient severity (APR-DRG severity scores) and hospital characteristics (geographic location, bed-size, teaching and urban hospital). Costs (total and departmental), days of stay in hospital(LOS), incidence of mortality and Catheter-Associated Urinary Tract Infection(CAUTI) were compared between groups using t-test for continuous variables and chi-squared test for categorical variable. Sub-groups of medical and surgical population were also matched and analyzed separately. RESULTS: Total of 86,398(2.1%) of all the selected patients experienced PAD. Post-matching mean total cost were significantly higher for the PAD group compared to NPAD group($33,945 vs. $22,380, p<0.0001). Mean costs associated with room & board, central supply, surgery, pharmacy and other miscellaneous departments were also significantly higher for PAD group(all p<0.0001). Compared to NPAD group, PAD group had higher mean LOS days(12.9 vs. 8.2) and also had a higher incidence of CAUTI(0.6 vs. 0.5%) and in-hospital mortality(8.6% vs. 7.8%) (all p<0.05). The results for sub-group analysis were also significant for total costs(Medical patients: $22,065 vs. 15,700; Surgical patients: $45,728 vs. $32,091) and LOS days(Medical patients: 11.4 vs. 8.3; Surgical patients: 17.8 vs. 11.4) (all p<0.05). CONCLUSIONS: PAD has a potential to add significant burden to hospital costs and resources. Adopting strategies aimed at avoiding PAD may help in reducing hospital cost and resource burden and may improve patient outcomes.