Diabetes mellitus (DM) is a chronic metabolic disorder characterised by elevated blood glucose levels (hyperglycaemia), caused by an imbalance between insulin supply and demand. Insulin is required to facilitate the entry of glucose into cells so that it can be utilised for cellular metabolism and growth. This study aimed to obtain an overview of patients’ knowledge regarding complications of diabetes mellitus at Daya General Hospital, Makassar, conducted from 14 to 28 January 2013. It was a descriptive analytical study using a crosssectional method with a sample size of 42 respondents who met the selection criteria through purposive sampling. Data were collected via a questionnaire. The collected data were processed and analysed using computerised methods with appropriate statistical tests. Data analysis included univariate and bivariate analyses using the Chi-Square test, with a significance level of α=0.05. H0 was rejected if p<0.05 and accepted if p>0.05. The results of this study indicate that there is a relationship between health education and knowledge (p = 0.003 < α = 0.05) and inpatient experience (p = 0.004 < α = 0.05) with patients’ knowledge of DM complications. Thus, the better the health education and the patient’s inpatient experience, the better the patient’s knowledge of DM complications.