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Glucose tolerance test
This document provides information about the glucose tolerance test (GTT), also known as the oral glucose tolerance test (OGTT). It defines the GTT as a standardized test used to diagnose diabetes mellitus in doubtful cases. The document outlines the indications for an OGTT as having symptoms of diabetes, inconclusive fasting blood sugar levels, pregnancy with excessive weight gain or history of large or miscarried babies. Contraindications are a confirmed diabetes diagnosis or using it for follow-up. Preparation involves a high carbohydrate diet before the test and fasting overnight. The test involves collecting fasting and 2-hour blood and urine samples after a glucose drink. Diagnosis of diabetes is made if fasting blood sugar is over 126 mg/dl or
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Glucose tolerance test
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- 2. CONTENTS DEFINITION INDICATIONFOR OGTT CONTRAINDICATION FOR OGTT PREPARATION OF THE PATIENT CONDUCTING THE GLUCOSE TOLERANCE TEST NORMAL VALUES ANND INTERPRETATION DIAGNOSTIC CRITERIA FOR DM
- 3. DEFINITION GTT iswell standardised test, and is highly useful to diagnose diabetes mellitus in doubtful cases Commonly referred to as oral glucose tolerance test (OGTT)
- 4. INDICATION FOR OGTT Patient has symptoms suggestive of diabetics mellitus Fasting blood sugar value is inconclusive (between 110 and 126 mg/dl) During pregnancy, excessive weight gaining is noticed, with a past history of big baby (more than 4 kg) or past history of miscarriage To rule out benign renal glucosuria
- 5. CONTRAINDICATION FOR OGTT Thereis no indication for doing OGTT in a person with confirmed diabetics mellitus GTT has no rule in follow-up of diabetics It is indicated only for the initial diagnosis The test should not be done in ill patients
- 6. PREPARATION OF THE PATIENT The patient is instructed to have good carbohydrate diet for 3 days before to the test Diet containing about 30-50 gm of carbohydrate should be taken on the evening before to the test (otherwise carbohydrate may not be tolerated even in a normal person) Patient should avoid drugs likely to influence the blood glucose levels Patient should not do smoking during the test
- 7. PREPARATION OF THE PATIENT(cont…) High effort exercise on the previous day is to be avoided Patient should not take food 8 PM the previous night Should not take any breakfast, this is to ensure 12 hours fasting
- 8. hours1 2 3 0 50 100 15 0 20 0 250 30 0 350 Renal threshol d Normalperson Alimentary glycouria Impaired GT Diabetes mellitus Plasmaglucose mg/dl
- 9. CONDUCTING THE GLUCOSE TOLERANCETEST 1. AT ABOUT 8 am, a sample of blood is collected in the fasting state, urine sample is also obtained 2. Glucose load dose: the dose is 75 g anhydrous glucose (82.5 g of glucose monohydrate) in 250- 300 ml of water 1. When the test is done in children, the glucose dose is adjusted as 1.75 g/kg body weight 3. Sample collection 4. WHO recommendation is to collect only for the fasting and two hours post glucose load samples of blood and urine, this is called as mini-GTT
- 10. NORMAL VALUES ANND INTERPRETATION In a normal person, fasting plasma glucose is 70- 110 mg/dl The glucose level rises and reaches a peak within hour and come down to normal fasting level by 2- 2:30 hrs, this is due to secretion of Insulin in response to the elevation in blood glucose None of the glucose sample shows the any evidence of glucose
- 11. DIAGNOSTIC CRITERIA FOR DM If the fasting plasma sugar is more than 126 mg/dl or more than one occasion If two hour post glucose load value of OGTT is more than 200 mg/dl If both fasting and 2 hrs values are above this level If the random plasma level is more than 200 mg/dl, on more than one occasion
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