The term ‘diabetes’ means excessive urination and the word ‘mellitus’ means honey. Diabetes mellitus is a lifelong condition caused by a lack, of insulin. Insulin is a hormone that is made by your pancreas. Insulin opens your cells, letting sugar in. For a patient with diabetes the pancreas makes too little insulin to allow all the sugar in your blood to get into your muscle and other cells to produce energy. If sugar can't get into the cells to be used, it builds up in the bloodstream. Therefore, one of the main characteristics of diabetes is high blood sugar levels.

There are two main types of diabetes: type 1 or insulin-dependent diabetes mellitus (IDDM), and type 2 formally know as non-insulin-dependent diabetes mellitus (NIDDM).

Type 1: This form has a sudden start usually before the age of 40, but can occur at any age. The beta cells in the pancreas which produce insulin are killed off by the person’s own body. Insulin treatment is essential for life and will always have to be taken. Without insulin, blood glucose levels become too high and fat is broken down as another source of energy. This results in the production of ketone bodies which, can lead to ketoacidosis. This in turn can cause nausea, vomiting and drowsiness, and can lead to diabetic coma. Insulin is currently given by injection or pump.

Type 2: This is the form that most people with diabetes have. It affects mostly people over the age of 40 and has a slow start that may go undiagnosed. People with type 2 diabetes still secrete insulin, though there is almost always some reduction in the quantity produced.

In Ireland, it is estimated that there are 200,000 people with diabetes and a further 200,000 who have diabetes but are unaware that they have the condition. A further 250,000 people have impaired glucose tolerance or "pre-diabetes" of which 50% will develop diabetes in the next 5 years if lifestyle changes are not made.