OBJECTIVES: Quantify the reductions in diabetic related complications associated with the addition of colesevelam hydrochloride to metformin in patients with type-2 diabetes who have not achieved optimal control. METHODS: The quantification of the effects of pharmacologic intervention on glycaemic control in type-2 diabetics and the quantification that improved glycaemic control reduces the risk of diabetic-related complications was measured in the UK, Germany and the USA using Generalized Estimating Equations (GEE) on longitudinal data. The three models quantified that pharmacologic intervention reduced HbA1c by 0.99%, 0.92% and 0.89%, respectively, (P<0.01). The second set of models quantified that a 1% reduction in HbA1c reduced the rate of complications by 0.388%, 0.414% and 0.436% (P<0.01). Using these validated equations, the efficacy data from a clinical trial comparing the addition of colesevelam hydrochloride to metformin versus metformin alone in type 2 diabetic patients who lack optimal control despite treatment was converted into reductions in the onset new diabetic-related complications. 5000 bootstrap samples of 100 patients from each treatment group were replicated to measure and minimize bias. RESULTS: In the first year, the addition of colesevelam to metformin reduces the number of diabetic related complications by 10,757 in 100,000 type-2 diabetics who lack glycaemic control despite treatment. The most prevalent of those complications are manifestations of neurological dysfunction (0.0166), disorders of the peripheral circulation (0.0170) and ischemic heart disease (0.0178). Treatment with coleselevam in these patients who had not achieved optimal control reduced those events by 1790 neurological disorders, 1829 peripheral circulatory disorders and 1917 new cases of ischemic heart disease. The number of events avoided by year two and three accrued to 18,173 and 27,505 per 100,000 patients. CONCLUSIONS: Effective treatment by adding colesevelam to metformin quantifiably reduces HbA1c and complications in patients who have not achieved control.