Introduction: The goals of this retrospective cohort study of 129,443 persons admitted to Calgary acute care hospitals 2013-2021 were to ascertain correlations of “potentially inappropriate medi-cations” (PIMs), “potential prescribing omissions” (PPOs) and other risk factors with readmissions and mortality. Methods: Processing and analysis codes were built in Oracle Database 19c (PL/SQL), R and Excel. Results: The percentage dying during their hospital stay rose from 3.03% during the first to 7.2% during the 6th admission. The percentage dying within 6 months of discharge rose from 9.4% after the first to 24.9 after the sixth admission. Odds ratios (adjusted for age, gender and comorbidities) for readmission were the post-admission number of medications (1.16; 1.12-1.12), STOPP PIMs (1.16; 1.15-1.16); AGS Beers PIMs (1.11; 1.11-1.11) and START omissions not corrected with a prescription (1.39 (1.35-1.42). Odds ratios for mortality were post-admission number of medications (1.04; 1.04-1.05), STOPP PIMs (0.99; 0.96-1.00); AGS Beers PIMs (1.08; 1.07-1.08) and START omissions not corrected with a prescription (1.56 (1.50-1.63). START omissions corrected with a prescription correlated with a dramatic reduction in mortality (0.51; 0.49-0.53). Odds ratios for readmissions for the second through 39th admission were consistently higher if START PPOs were not corrected for the second admission (1.41; 1.36-1.46), third (1.41;1.35-1.48); fourth 1.35;1.28-1.44); fifth 1.38; 1.28-1.49); sixth (1.47;1.34-1.62) and 7th through 39th admission (1.23; 1.14-1.34). For all admissions when a pre-scription was given to correct START PPOs ORs for mortality within six months of discharge were dramatically improved (0.51; 0.49-0.53). This was also true for the second (0.52; 0.50-0.55; fourth (0.56; 0.52-0.61; fifth (0.63; 0.57-0.68); sixth (0.68; 0.61-0.76); and 7th through 39th admissions (0.71; 0.65-0.78). Conclusions: PPOs should be corrected by prescriptions and teams of family physicians, pharmacists and nurses should focus on patients’ understanding of their illnesses, medications and ability for self-care.