Diagnosis of diabetes
Diabetes is diagnosed by measuring the amount of glucose in a blood sample. The test is usually performed after an overnight fast. If the glucose level is above 7 mmol/litre on a fasting glucose test, diabetes is diagnosed.
If the results of this initial test are not clear, a second test called an oral glucose tolerance test may be used. This test measures the amount of glucose in the blood before and after a glucose drink has been given. If the glucose level is equal to or greater than 11.1 mmol/litre two hours after the drink, diabetes is diagnosed.
The type of diabetes (whether type 1, type 2 or gestational) will normally be apparent from signs and symptoms that are present at the time of diagnosis, and from the person’s age – type 1 diabetes is associated with younger age and type 2 with older age.
Type 1 diabetes typically occurs with a pattern of symptoms that develop rapidly, and may be accompanied by unexpected weight loss. The presence of a substance called ketones in the urine is another characteristic feature of type 1 diabetes – ketones are unlikely to be found in type 2 diabetes. In some cases, a test for antibodies to pancreatic cells may be done to distinguish type 1 diabetes from type 2.
People with type 2 diabetes tend to develop symptoms more slowly. They are likely to be overweight or to have some other sign of the metabolic syndrome, a medical condition associated with type 2 diabetes. Other signs of the metabolic syndrome are an increased waistline, high blood pressure, low levels of HDL cholesterol (a type of cholesterol that protects against heart disease) and high levels of triglycerides, another type of fat that is found in the bloodstream.
Diabetes that is diagnosed for the first time in a woman who is pregnant is, by definition, gestational diabetes.