Drugs that protect against cardiovascular events in the patient with diabetes may also positively or negatively affect glycaemic control in the patient with established diabetes and may induce the development of diabetes in the predisposed patient. Mainly through increasing insulin resistance, beta‐blockers, statins and high‐dose diuretics have the potential to worsen glycaemic control. Dihydropyridine calcium channel blockers, low‐dose diuretics, vasodilating beta‐blockers, alpha‐blockers and pitavastatin have little or no effect on glycaemic control. Blockers of the renin‐angiotensin‐aldosterone system, colesevelam, ranolazine and verapamil, through slowing breakdown of bradykinin, vasodilation, increasing cholecystokinin levels, blocking sodium channels and decreasing beta cell apoptosis, may improve glycaemic control and avoid the development of diabetes.