INTRODUCTION: Mortality due to COVID-19 is higher among elderly patients with comorbidities. Even so, prognostication in COVID-19 remains limited. METHODS: We assessed 90-day mortality stratified by comorbidities, routine biochemical markers and oxygen need in a consecutive single-centre cohort from 2 March to 2 June 2020. RESULTS: We included 263 hospitalised patients with laboratory-confirmed COVID-19. On admission, fitness for intensive care was determined in 254 patients including 98 (39%) with a do-not-resuscitate order. Ninety-day overall mortality was 29%, whereas intensive care unit (ICU) mortality was 35% (14/40). Alcohol abuse, liver disease and elevated urea were strongly associated with mortality in univariable analyses. In a mutually adjusted multivariable analysis, we found an independent incremental increase in 90-day mortality with each increasing age by decade (hazard ratio (HR) = 1.5; 95% confidence interval (CI): 1.2-1.9), Charlson Comorbidity Index (CCI) score (HR = 1.2; 95% CI: 1.0-1.4), number of abnormal blood tests (HR = 1.2; 95% CI: 1.1-1.3) and l/min. of supplemental oxygen (HR = 1.1; 95% CI: 1.1-1.2). CONCLUSIONS: The overall mortality was similar to that of other hospitalised patients, whereas the ICU mortality was lower than expected. On admission, each additional age by decade, CCI score, number of abnormal blood tests and magnitude of supplemental oxygen were independently associated with increased mortality.