How Diabetes is Diagnosed

Your doctor can diagnose diabetes with simple blood and urine tests.

Diagnosis of type 1 diabetes

In type 1 diabetes, the diagnosis is suggested by such typical complaints as increased thirst and urination, sometimes followed by weight loss. The diagnosis can be made using two simple tests:

• a casual blood glucose level greater than 11mmol/L (millimoles per litre)
• a positive test for ketones in the urine

Ketones are acids produced from fat breakdown. High levels of ketones occur when there is not enough insulin in your system.

Diagnosis of type 2 diabetes

Type 2 diabetes may sometimes have the same symptoms as type 1 diabetes, or a woman may have frequent vaginal yeast infections. More often, however, there are no symptoms and the diagnosis is made on the basis of a blood glucose test. The recommended test is a fasting blood glucose. A fasting blood glucose is done after you have not eaten for at least eight hours. This means the test is usually done early in the morning. Any fasting blood glucose of 7 mmol or greater indicates diabetes.

A second blood test done on a different day is necessary to confirm the diagnosis, unless a high blood glucose level is accompanied by many symptoms of diabetes. A glucose tolerance test (described below) is not routinely needed to diagnose diabetes.

Diagnosis of Gestational Diabetes

Between the 24th-28th week of pregnancy, women may be screened for gestational diabetes. This screening test involves drinking a 50-gram glucose drink and having blood drawn one hour later. If the blood glucose reading is between 7.8mmol/L and 10.3 mmol/L, an oral glucose tolerance test should be done to confirm the diagnosis. If blood glucose is above 10.3 mmol/L, gestational diabetes is present and an oral glucose tolerance test is not required.

For the oral glucose tolerance test, you will be asked to fast overnight and then your blood glucose level will be measured. You will then be asked to take a drink containing 75 grams of glucose. Blood tests are done again one hour and two hours afterwards. At least two of the following blood glucose values need to be met or exceeded for GDM to be diagnosed:

• fasting value of 5.3mmol/L
• 10.6mmol/L after one hour
• 8.9mmol/L after two hours