OBJECTIVES: The rising prevalence of overweight and obesity has led to an increase in related metabolic disorders; most notably t2dm. We sought to determine how the cost of medication for this condition varies within a cohort of patients attending Galway University Hospital, according to age, gender, BMI and co-morbidity status. METHODS: We identified a subgroup of 185 adult type 2 diabetes patients attending our university hospital-based diabetes clinic, for whom detailed information about drug therapy and comorbidities (obesity, hypertension, dyslipidaemia) was available. We modelled the lifetime costs of medications for each patient, taking account of age, gender and comorbidity. The analysis compares the lifetime cost of medication of those patients who are obese relative to those who are overweight and of those with fewer to those with more co-morbidities; specifically obesity, hypertension and dyslipidaemia. RESULTS: We found that obesity is associated with a higher cost of medication relative to being overweight. Those with a BMI range of 35-39.9 had the highest mean cost of medication, costing on average €615 more than those who are overweight (p<.01). The highest cost of medication was associated with those aged 50-65- non-significant. Among those having all three co-morbidities compared to those having only t2dm there was a significant difference in the cost of medication costing on average an extra €418 (p<.05).  CONCLUSIONS: These results suggest that the health economic costs associated with t2dm are differential with respect to the BMI status of affected individuals. These findings are of use in understanding the drug related burden of illness associated with obesity, t2dm and also the burden associated with being obese when one has t2dm compared to not being obese and having it. This study generated interesting data which will need to be replicated in larger prospective multicentre cohort studies.