Type 1 Diabetes: Diagnosis

Also known as: Postprandial plasma glucose test.

What is it? A blood test which measures the body's ability to metabolize carbohydrates and produce insulin. Postprandial means after meal, and this test is administered two hours following a meal.

Why is this test performed? To screen for diabetes or confirm results from the fasting plasma glucose test. The test is also used to evaluate the effectiveness of medication or dietary therapy in those already diagnosed with diabetes.

How frequently should this test be performed? Once for diagnostic purposes, or as required when monitoring a treatment regime.

What is the "normal" range for results? Generally, levels of less than 145 mg/dl (8.1 mmol/L) are considered normal (when using the glucose oxidase or hexokinase laboratory methods). Normal results also vary by age. Individuals age 50 and older will have slightly higher levels than those under this age range. Certain medications and recent illnesses can influence glucose levels, and should be taken into consideration when interpreting test results.

What do abnormal results mean? Two-hour postprandial glucose values of 200 mg/dl or higher indicate diabetes. Further lab tests may be required to confirm this diagnosis. Other conditions which may result in an elevated result include pancreatitis, Cushing's syndrome, liver or kidney disease, eclampsia, and other chronic and acute illnesses.

A lab result which measures below the normal range can indicate problems such as reactive hypoglycemia, renal or hepatic insufficiency, hypopituitarism, or malabsorption syndrome, and will usually require further diagnostic testing.