Patients develop Type 2 diabetes because of a combination of genetic susceptibility and lifestyle triggers. However, the genetics behind Type 2 diabetes are complicated and still incompletely understood. Unlike other genetic traits (for example, eye colour), its inheritance is not easily predicted. There are thought to be multiple genes involved in the inheritance of diabetes and the interplay between these genes is still incompletely understood. This is why someone with diabetes may not necessarily have parents or siblings with diabetes, however they are more likely to. Certain ethnic groups such as South Asians, Indians and Aboriginal Australians have a greater tendency to develop Type 2 diabetes.

There's a strong link between lifestyle and the manifestation of Type 2 diabetes. Type 2 diabetes is known to be associated with excess weight, sedentary lifestyle and a high carbohydrate diet. Lifestyle measures underpin the success of all other treatments of diabetes.