How to do a glucose tolerance test

Methods of oral glucose tolerance test

1. OGTT should be performed on an empty stomach in the early morning after 8 hours without any calorie intake. Oral administration of 75 grams of anhydrous glucose powder dissolved in 250-300 ml of water or 2 taels of standard steamed bread. If 1 molecule of water glucose is used, the dose is 82.5. For children, give 1.75 per kg of body weight, with a total amount not exceeding 75. Drink the sugar water within 5 minutes. Start timing from the first sip of sugar, and draw blood from the forearm to measure blood sugar before, and half an hour, one hour, two hours, and three hours after taking the sugar. During the trial, the subjects were not allowed to drink tea or coffee, smoke, or do strenuous exercise, but they did not need to stay in bed. Blood samples should be sent for examination as soon as possible.

2. Within 3 days before the test, the daily carbohydrate intake should be no less than 150. Starting from 7-9 am, the subjects took 75% of anhydrous glucose powder dissolved in 300ml of water orally after fasting (8-10 hours). If 1 molecule of water glucose is used, the amount would be 82.5%. For children, give 1.75 per kg of body weight, with a total amount not exceeding 75. Drink the sugar water within 5 minutes.

3. Start timing from the first sip of sugar, and draw blood from the forearm to measure blood sugar 2 hours before and after taking the sugar. During the trial, the subjects were not allowed to drink tea or coffee, smoke, or do strenuous exercise, but they did not need to stay in bed. Blood samples should be sent for examination as soon as possible. During the 3 days before the test, the daily carbohydrate intake should be no less than 150. Stop taking any drugs that may affect OGTT, such as birth control pills, diuretics, or phenytoin sodium, for 3-7 days before the test.

2. Clinical Significance

1. Normal glucose tolerance: FBG ≤ 6.1mmol/L, OGTT 2-hour blood glucose < 7.8mmol/L.

2. Impaired fasting glucose (IFG): FBG 6.1-6.9 mmol/L, OGTT 2-hour blood glucose <7.8 mmol/L.

3. Impaired glucose tolerance (IGT): FBG <7.0mmol/L. Impaired glucose tolerance (IGT) is seen in: ① the transition stage between abnormal glucose metabolism and diabetes (or prediabetes); ② severe liver disease; ③ others: hyperthyroidism, pancreatitis, pancreatic cancer, etc.

4. Increased glucose tolerance: more common in endocrine dysfunction, such as hypothyroidism, hypopituitarism, etc.

3. Notes

1. During the trial, patients should avoid strenuous exercise and physical labor, rest quietly, not smoke, and fasting from food and water.

2. For patients suspected of reactive hypoglycemia, extend the test time and measure blood sugar 4 and 5 hours after taking sugar.

3. Observe the patient's reaction after taking sugar. If the patient becomes pale, nauseous, or faints during the test, the test should be stopped. If the above symptoms appear 3 to 4 hours after taking sugar, hypoglycemia should be considered. Blood should be drawn immediately to check blood sugar. The patient should be advised to eat foods such as porridge and steamed buns, and changes in the condition should be closely observed.

4. Blood sugar should be tested immediately after being collected.