Glucose tolerance test

Possible interpretation of the results

Interpretation of basal blood glucose values ​​and glucose tolerance test is performed according to ADA (American Diabetes Association) criteria:

At least two abnormal glucose tolerance tests are required to diagnose diabetes.

The glucose tolerance test is useful not only for diagnosing diabetes but also for identifying patients with impaired glucose tolerance (IGT).

People with IFG (increased glucose tolerance) as well as individuals with IGT are part of an intermediate group who, although they do not meet the diagnostic criteria for diabetes, have too high a glucose level to be considered normal. These people were previously considered to have prediabetes, but according to the new ADA (2010) recommendations, IFG and IGT should not be considered as independent clinical units, but as high-risk categories in the development of diabetes and cardiovascular disease. IFG and IGT are associated with obesity (especially in the abdomen), high blood pressure, and dyslipidemia (high triglycerides and low HDL-cholesterol). Increased physical activity, weight loss, and the intake of certain pharmacological agents prevent or slow down the development of diabetes in people with glucose intolerance.

Other clinical conditions related to glucose tolerance:

• Decreased glucose tolerance may occur with high blood sugar: postgastrectomy, excessive glucose uptake, type III, IV and V hyperlipidemia, hemochromatosis, Cushing's disease, CNS damage.
• Decreased glucose tolerance with hypoglycemia may occur: von Gierke's disease, severe liver disease, elevated epinephrine levels.
• Increased glucose tolerance with a flattened curve (obtained from blood glucose readings 30, 60, 90, 120, 180 min) may occur: Hyperplasia or pancreatic islet cell carcinoma, malabsorption (Sprue, celiac disease, Whipple disease), Addison's disease, Hippo's disease, Hypo Liver disease.

Diagnostic limitations

The test has limited relevance in the diagnostics of diabetes in children and is rarely used for this purpose.

• Smoking can increase glucose levels.
• A modified diet (eg weight loss regimen) can lower glucose tolerance and lead to "false diabetes".
• Infectious diseases and surgery can affect glucose tolerance, so testing is recommended within 2 weeks of an acute episode.
• Other pathological conditions that can lead to false pathological results during the glucose tolerance test: duodenal ulcer, gastrectomy, hypokalemia, hypermagnesemia.