The characteristics and mortality outcomes of patients admitted to South African intensive care units (ICUs) owing to medical conditions are unknown. Available literature is derived from studies based on data from high-income countries. To determine ICU utilisation by medical patients and evaluate the scope of admissions and clinical associations with hospital mortality in ICU patients 12 years and older admitted to an Eastern Cape tertiary ICU, particularly in the subset with HIV disease. A retrospective descriptive one-year cohort study. Data were obtained from the LivAKI study database and demographic data, comorbidities, diagnosis, and mortality outcomes and associations were determined. There were 261 (29.8%) medical ICU admissions. The mean age of the cohort was 40.2 years; 51.7% were female. When compared with the surgical emergencies, the medical subgroup had higher sequential organ failure assessment (SOFA) scores (median score 5 v. 4, respectively) and simplified acute physiology score III (SAPS 3) scores (median 52.7 v. 48.5), a higher incidence of acute respiratory distress syndrome (ARDS) (7.7% v. 2.9%) and required more frequent dialysis (20.3% v. 5.5%). Of the medical admissions, sepsis accounted for 32.4% of admission diagnoses. The HIV seroprevalence rate was 34.0%, of whom 57.4% were on antiretroviral therapy. ICU and hospital mortality rates were 11.1% and 21.5% respectively, while only acute kidney injury (AKI) and sepsis were independently associated with mortality. The HIV-positive subgroup had a higher burden of tuberculosis (TB), higher admission SOFA and SAPS 3 scores and required more organ support. Among medical patients admitted to ICU, there was a high HIV seroprevalence with low uptake of antiretroviral therapy. Sepsis was the most frequently identified ICU admission diagnosis. Sepsis and AKI (not HIV) were independent predictors of mortality. Co-infection with HIV and TB was associated with increased mortality. The epidemiology and outcomes of adults who are critically ill from medical conditions in South African intensive care units was previously unknown but has been described in this study. The association of sepsis, TB, HIV and acute kidney injury with mortality is discussed.