Introduction Metformin-associated lactic acidosis (MALA) is a classic side effect of metformin and is known to be a severe disease with a high mortality rate. The treatment of MALA with dialysis is controversial and is the subject of many case reports in the literature. We aimed to assess the prevalence of MALA in a 16-bed, university-affiliated, intensive care unit (ICU), and the effect of dialysis on patient outcome. Methods Over a five-year period, we retrospectively identified all patients who were either admitted to the ICU with metformin as a usual medication, or who attempted suicide by metformin ingestion. Within this population, we selected patients presenting with lactic acidosis, thus defining MALA, and described their clinical and biological features. Results MALA accounted for 0.84% of all admissions during the study period (30 MALA admissions over five years) and was associated with a 30% mortality rate. The only factors associated with a fatal outcome were the reason for admission in the ICU and the initial prothrombin time. Although patients who went on to haemodialysis had higher illness severity scores, as compared with those who were not dialysed, the mortality rates were similar between the two groups (31.3% versus 28.6%). Conclusions MALA can be encountered in the ICU several times a year and still remains a life-threatening condition. Treatment is restricted mostly to supportive measures, although haemodialysis may possess a protective effect.