What is diabetes?

Diabetes is a chronic condition marked by high levels of glucose in the blood. It is caused either by the inability of the body to produce insulin (a hormone made by the pancreas to control blood glucose levels) or by the body not being able to use insulin effectively, or both. The main types of diabetes are explained in Box 1.

Box 1: Types of diabetes

Type 1 diabetes

Type 1 diabetes is a lifelong autoimmune disease that usually has onset in childhood or early adolescence. The exact cause is unknown but it is believed to be the result of an interaction of genetic and environmental factors. A person with type 1 diabetes requires daily insulin replacement to survive, except in cases where a pancreatic transplant occurs.

Type 2 diabetes

The most common form of diabetes, generally having a later onset than type 1 diabetes, people with type 2 diabetes produce insulin, but do not produce enough, and/or cannot use it effectively. It involves a genetic component, but is largely preventable and is often associated with lifestyle factors including physical inactivity, poor diet, being overweight or obese, and tobacco smoking. Type 2 diabetes can be managed with changes to diet and exercise, oral glucose-lowering medications, non-insulin injectable glucose-lowering medications, insulin injections, or a combination of these methods.

Gestational diabetes

Gestational diabetes is characterised by glucose intolerance of varying severity that develops or is first recognised during pregnancy, mostly in the second or third trimester. It usually resolves after the baby is born, but can recur in later pregnancies and significantly increases the risk of developing type 2 diabetes in later life, both for the mother and the baby. Gestational diabetes can be often managed with changes to diet and exercise, while some cases require treatment with medication.

Other types of diabetes

Other types of diabetes are relatively uncommon, and are most typically related to certain conditions or syndromes that result in defects in insulin secretion, insulin action, or both. For some people with other types of diabetes, adequate glycaemic control can be achieved through diet and exercise or use of other medications. Some however, may also require insulin to manage their blood glucose.