Insulin is a protein-based hormone needed to allow glucose, or sugars, to be taken up by the body's cell tissues and used as energy. Insulin gets released by the pancreas. Insulin production, along with diet, regulates how much glucose is in the bloodstream, for it is insulin that enables cells to take the glucose out of the blood and past their cell walls and inside the cells. Glucose is the first fuel that the body burns, and the brain lives on it.
If you are low in insulin production or cannot utilize insulin properly, the sugars mostly just stay in your bloodstream and build to very high levels. This leads to the symptoms of diabetes: excess weight or obesity; dehydration (the body tries to flush out the excess sugars); eventual harm to your body (nerves, kidneys, and/or heart); lack of energy and lack of mental powers (lack of cellular fuel); chronic skin infections; gum disease/tooth decay; foot infections (poor circulation); and blurry vision.
One way of managing type 2 diabetes and minimizing these complications is taking commercially prepared insulin to force more insulin into your bloodstream. Various types of medication are also available, such as the commonly-used Metformin or Glucophage. While it's not uncommon for type 2 diabetics to use medication or insulin, it is only one part of a treatment regimen, and it's sometimes not needed at all - some people are able to control diabetes without the need for medication.
Diet and exercise, along with extra careful monitoring of one's body for any signs of escalating symptoms, are the strongest methods of minimizing the ill effects of diabetes. The goal is to regulate the intake of glucose so that blood sugar does not fluctuate too far out of normal range throughout the day. This will include paying attention to foods' glycemic index, a measurement of how many and what types of carbohydrates are contained in a given portion of the food in question. Carbohydrates are starches and sugars, and they come in two different types: simple and complex. Simple are easier to digest, complex more difficult. Complex "carbs" give longer lasting energy (to everybody, not just diabetics) and only demand a slow, gradual release of insulin into the bloodstream.
A diabetic will, therefore, want to have a diet heavy on fresh whole fruits (not juices) and vegetables and whole grains like whole grain bread, whole wheat pasta, and brown rice. Commercially-prepared foods like canned fruits and vegetables have to be monitored closely - these are very often quite high in refined sugars or salt (diabetics must watch salt intake because of how easily they are dehydrated). Refined foods like white bread, white rice, and sugar should be minimized in the diet. Of course, soda pop and other sweets must be minimized. Dairy products must also be watched closely because they contain a lot of simple carbs as well. Portion control is important for both regulating the carbohydrate intake as well as for overall weight maintenance. Extra calories add up and can lead to weight gain, which makes diabetes harder to control.
Finally, exercise helps to control blood sugar levels. Diabetics need to get plenty of physical exercise in order to prevent their bodies from storing too much glucose. Even simple exercising that blends into your daily life (such as gardening, or walking or riding a bicycle to do chores) are beneficial to help get blood sugar down.