Diabetes is a chronic disease in which insulin production and/or tissue sensitivity to insulin is impaired. As a result, circulating blood sugar (glucose) levels rise (i.e. hyperglycaemia, an excess of sugar in the bloodstream).

Normally, when we eat or drink, the carbohydrates in our diet are digested and broken down into small sugar molecules called glucose. Glucose is then absorbed into the bloodstream, so that it can supply energy to various tissues and organs throughout the body, especially the muscles, brain and liver cells. The amount of glucose produced from a particular food or drink depends on its glycaemic index. Examples of food containing carbohydrates include starchy foods such as potatoes, bread, pasta, oats, fruits and vegetables.