How is diabetes diagnosed?

Diabetes is usually diagnosed through 2 abnormal pathology results or through 1 abnormal pathology result in the presence of symptoms of hyperglycaemia (high blood glucose levels – more about this a little later).

The abnormal results could be:

  • Abnormal fasting blood glucose levels (FBGLs), usually taken first thing in the morning
  • Abnormal non-fasting blood glucose levels (BGLs – also referred to as post-prandial blood glucose levels (PPBGLs) or random BGLs), these can be taken at any time during the day.
  • A combination of an abnormal fasting level with an elevated post-prandial BGL.

Some people are recommended to get an oral glucose tolerance test (OGTT) done.  When an oral glucose tolerance test is requested it is essential that the person is fasting, as the first sample of blood that is taken is the FBGL.  The patient is then given a sweet drink which contains 75g of glucose (in some cases a 50g or 100g load could also be used).  This drink must be consumed within 5 minutes and blood glucose levels are measured an hour and two hours after the drink.  It is important to remain seated throughout the OGTT as moving around could influence the results.  Some patients are asked to increase their carbohydrate intake for 3 days preceding the OGTT, in an effort to reduce the risk of false positive results, though generally these days’ people consume plenty of carbohydrates anyway and hence a special diet may no longer be required.  OGTTs are particularly popular to diagnose gestational diabetes.

As more research is being done, we learn more and more about diabetes and hence more and different forms of diabetes are discovered with time.  At the time of writing this I am aware that research is being undertaken to learn more about a type of diabetes referred to as Mitochondrial Diabetes and one referred to as Glucose-Kinase-C (or GCK for short).  But as yet, little remains known about these mixed and newer forms of diabetes and therefore I will not elaborate on these in this forum.

Steroid Induced Diabetes, No Other Diabetes After Transplant (NODAT), are a few of the other types of diabetes that have so far been identified.  There are different types of diabetes discovered on a regular basis and some experts in the field are suggesting we may need to look at reorganising groups of diabetes, based on the physical problem that occurs, to get clearer diagnoses for people, but at the time of writing this they are far from reaching a consensus on this topic.

If you have recently been diagnosed with diabetes or if you have had diabetes for some time, but your levels are not quite to target or you have some questions: call Carolien for more information: 0402 126 212 or email:

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