Note that even if all the risk factors are present in the same person it doesn't mean that they will certainly develop diabetes.

It is important to have a good understanding of the risk factors associated with diabetes, that is, the circumstances that make it more likely that diabetes will develop. Knowing these risk factors can help you make a diagnosis, especially of Type 2 diabetes, and introduce treatment at an early stage. The main risk factors for Type 2 diabetes are listed below:

A family history of diabetes (genetic factors).
Being overweight or obese; the distribution of body fat also appears to be important, with fat around the abdomen seen as more of a risk than fat hips.
Lack of exercise.

There is some indication that a virus infection in early childhood might lead to Type 1 diabetes in some cases; the theory is that the virus in some way causes the person's own immune system to destroy the insulin-producing cells in their pancreas.