The best way to check if you have diabetes or are at risk is to visit your local health centre. They can check your blood glucose (sugar) levels there and assess any symptoms you may have.
This chart shows the different levels of blood glucose, what are safe levels and what are dangerous levels depending on when you last ate. Your health worker can explain this in more detail when you are getting tested.
Even if you have no symptoms at all, it is important to get tested as you may still have diabetes.