The Importance of Fasting Glucose and Postprandial Blood Sugar on Diabetic Diagnosis

Two-hour postprandial blood sugar test (2-h PPBS) is also very important. It is easier to find problems at this time because the blood glucose is relatively higher. For patients with type II diabetes mellitus, their fasting glucose may be in a normal range, but their 2-h PPBS are quite high. Therefore, the 2-h PPBS are more important than fasting glucose sometimes. Unfortunately some hospitals do not realize the importance of 2-h PPBS and they only diagnosticate diabetes by fasting glucose. It causes many missed diagnosis. Healthy people’s 2-h PPBS are lower than 7.8mmol/L (140mg/dL) or will be considered elevation of blood glucose. The person might be diagnosed with diabetes if his 2-h PPBS is equal or greater than 11.1mmol/L (200mg/dL).

Normal range of fasting glucose is between 3.3~6.1mmol/L (60~110mg/dL), and the normal range of 2-h PPBS is between 3.3~7.8mmol/L (60~140mg/dL), values higher than these maximums are abnormal. Patients who are suspected diabetes mellitus need further examinations to clarify their glycometabolism. And glucose tolerance test is one important factor of those tests.

Oral glucose tolerance test (OGTT) measures the patient’s ability to metabolize glucose. OGTT should be done with an empty stomach. For this test, you will be asked to drink 300ml water with 75g glucose. Your blood will be taken before you drink. And then your blood will be taken after 30 minutes, 1 hour and 2hours respectively. These values of blood glucose help to diagnose diabetes. This concentration of glucose may not irritate the stomach. For children, their glucose intake is calculated by 1.75g/KG.

Things you need to prepare before the test:

1. Starting to ensure adequate carbohydrate 3 days before the test. Generally speaking, the carbohydrate intake should not less than 250g per day or the glucose tolerance will be lower factitiously.

2. Medications might affect the test should be stop for a period of time. These medications include diuretics, glucocorticoid hormone (cortisone) and oral contraceptives.

3. Nothing by mouth for 10~14 hours before the test (you can’t eat or drink anything after midnight before the test).

4. During the test, the liquid should be drunk in 5 minute after blood drawing.

5. No heavy exercise and much water intake during the test. No drinking of irritate beverages (wine, coffee) and smoking neither.

6. To cooperate the test on time.

It is obvious that both fasting glucose and postprandial blood glucose are important on the diagnosis of diabetes mellitus. Although venous blood glucose is the main factor to diagnose diabetes mellitus, fasting glucose and postprandial blood glucose as two adjunctive tests are also very important.

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