Oral Glucose tolerance test is a diagnostic method for diabetes.
When fasting blood glucose concentration does not reach the diagnostic criteria for diabetes but there is suspicion of diabetes, this test can be performed. Common methods include intravenous glucose tolerance test (IVGTT) and oral glucose tolerance test (OGTT). Currently, hospitals mostly adopt the OGTT.
1.Indications for OGTT:
Individuals with normal or slightly elevated fasting blood glucose who occasionally have positive urine sugar; follow-up patients with previously reduced glucose tolerance; patients suspected of having diabetes; individuals with elevated blood glucose after meals but not reaching the diagnostic criteria; and differentiation of other types of diabetes.
2.OGTT method:
In recent years, the World Health Organization (WHO) has established that adults should use 75g of glucose (children according to 1.75g/kg of body weight, with a total amount not exceeding 75g), mix it with 250~350ml of water after drawing fasting blood, and drink it all within 5 minutes. Blood samples are taken from the vein to measure blood glucose at 0.5, 1, 2, and 3 hours after drinking the sugar water, and the test can be extended to 4-5 hours if necessary. Generally, urine is collected during each blood draw to check for urine sugar.
3.Precautions for OGTT:
Do not overly limit carbohydrate intake before the test and avoid stimulating foods. Fast for 10-16 hours before the test, rest for half an hour before the test, and exclude other secondary factors that may cause elevated blood glucose, such as endocrine diseases. At least 3-7 days before the test, refrain from using corticosteroids, thiazide diuretics, salicylate preparations, oral contraceptives, and other medications that may affect the test results. During the test, in hot weather, separate the samples and store them in a refrigerator (4°C) or directly determine the results to avoid the impact of temperature on the results.
4.OGTT results:
Normal individuals (15-50 years old) have fasting blood glucose levels of 3.9-6.1mmol/L, with the peak blood glucose concentration occurring at 0.5-1 hour, generally less than 9.4mmol/L. Some people advocate <10mmol/L. The blood glucose level returns to normal range or less than 7.2mmol/L at 2 hours, and drops to normal at 3 hours. The urine sugar qualitative test is negative each time.
