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Types of diabetes

There are two main types of diabetes: Type 1 (which used to be called insulin dependent diabetes or juvenile diabetes) and Type 2 (which used to known as non-insulin dependent diabetes or adult onset diabetes). In addition, gestational diabetes is a term used to describe diabetes which is recognised for the first time during pregnancy. Pancreatic disease or damage can also cause diabetes if the insulin producing beta cells are destroyed.

Type 1 diabetes is present in about 0.5% of the population in Australia. Most cases of type 1 diabetes are diagnosed in those under the age of 30. Symptoms often develop abruptly and the diagnosis is often made following an emergency admission to hospital. The patient may be seriously ill, even unconscious, with very high glucose levels and high levels of ketones (byproducts that result from the use of fat as an alternative energy source when glucose is unavailable). Type 1 diabetics make very little or no insulin. Any insulin producing beta cells patients have at the time of diagnosis are usually completely destroyed within 5 to 10 years leaving them entirely reliant on insulin injections.

The exact cause of type 1 diabetes is unknown, but a family history of diabetes, viruses that injure the pancreas, and autoimmune processes (where the body's own immune system destroys the beta cells) are all thought to play a role. Type 1 diabetics may have more severe medical complications than other forms of diabetes. For instance, currently 40% of those with type 1 diabetes develop serious kidney problems leading to kidney failure by the age of 50.

Type 2 diabetes is estimated to be present in over 5% of the population of Australia but about half of those affected do not know they have the disease. Type 2 diabetics do make their own insulin but it is not in a sufficient amount to meet their needs because their body has become resistant to its effects. At the time of diagnosis they may have typical symptoms of diabetes, especially thirst, weight loss or may be passing large amounts of urine, or they may not have any symptoms, and diagnosis may be made on finding high glucose concentrations in the blood. It generally occurs later in life, in those who are obese, sedentary and over 45 years of age. Risk factors include:

  • Weight excess / obesity
  • Lack of exercise
  • Family history of diabetes
  • Any abnormality of glucose tolerance – the Oral Glucose Tolerance Test (OGTT-see later) may identify individuals whose ability to handle a high glucose meal is not normal but is not sufficiently abnormal to identify them as diabetic
  • Ethnic groups - more common in indigenous Australian, Polynesian, Asian and African-Caribbean communities
  • Gestational diabetes during pregnancy or baby weighing more than 9 pounds
  • High blood pressure
  • High triglycerides, high cholesterol, low HDL

Because the population of the western world is becoming more obese and not getting enough regular exercise, the number of those developing type 2 diabetes is rising and, of particular concern is its development in young people.

Gestational diabetes is usually a temporary type of hyperglycaemia seen in some pregnant women, usually during the second or third trimester. The cause is unknown, but it is thought that some hormones from the placenta increase insulin resistance in the mother causing elevated blood glucose levels. In Australia, gestational diabetes is usually diagnosed by an oral glucose tolerance test performed between the 24th and 28th week of pregnancy or earlier if the woman is at high risk. If gestational diabetes is not treated, the baby is likely to be larger than normal, be born with low glucose levels, and be born prematurely. Gestational diabetes also raises the risk of eventually developing type 2 diabetes, for both the mother and the baby.

Impaired fasting glucose or impaired glucose tolerance (sometimes referred to as ‘pre-diabetes’) are conditions which can only be detected by use of the oral glucose tolerance test and are characterised by glucose levels that are higher than normal, but not high enough to be diagnosed as diabetes. Usually these individuals do not have any symptoms but if nothing is done to lower their glucose levels, they are at great risk of developing diabetes. Recognising these conditions is important as recent evidence shows that progression to diabetes can be markedly reduced by simple measures such as a small amount of weight loss and exercise.

Last Review Date: May 9, 2015