HEALTH: the lowdown on impaired glucose tolerance

If your doctor has diagnosed impaired glucose tolerance, it doesn’t mean you have diabetes, but it does mean taking care of your body. It’s a warning sign, says Professor Kerryn Phelps.

Impaired glucose tolerance (IGT) is also known as pre-diabetes because once you have it you have a much higher risk of developing type 2 diabetes, as well as cardiovascular disease. Two million Australians have pre-diabetes and one in three will go on to develop type 2 diabetes, unless they make some changes.

If you have impaired glucose tolerance it means your body does not process glucose (a form of sugar) effectively. There are usually no symptoms, so the first clue is a blood test that shows your blood glucose is higher than the ideal range, but not high enough to be diagnosed as diabetes. As

GPs, there are some patients that we monitor more closely for impaired glucose tolerance. These include women with polycystic ovary syndrome (PCOS) or a history of gestational (pregnancy) diabetes, and patients who are overweight, have a

family history of diabetes or heart disease, and people with a sedentary lifestyle.

Your body relies on the hormone insulin, produced in your pancreas, to transport glucose into body cells to provide the energy you need for all of your body functions. Impaired glucose tolerance happens when the pancreas either does not release enough insulin or the cells become resistant to the insulin.

If you have a blood test that shows a higher glucose level than we would like to see, the next step is to arrange what we call a two-hour oral glucose tolerance test (or OGTT). You go for a fasting blood test, usually before breakfast, to get a baseline reading. You then drink a standard dose of glucose (a very sweet drink) and wait one hour for another blood test, then at two hours you have a third blood test. This is to see how your body deals with the glucose load over time.

If your glucose level is elevated after two hours, but not high enough to be in the diabetes range, then you fit the criteria for impaired glucose tolerance. What do you do next? The box, right, gives practical solutions for this common condition.