The document defines and describes the glucose tolerance test (GTT), also known as the oral glucose tolerance test (OGTT). It provides information on: - Indications for the GTT include diagnosing diabetes in doubtful cases, during pregnancy with risk factors, and to rule out renal glycosuria. - Contraindications include confirmed diabetes and using it for follow-up rather than initial diagnosis. - The test involves fasting overnight, drinking a glucose load, and having blood samples taken at baseline and 2 hours to measure the blood glucose response. - Normal values are a fasting blood glucose below 110 mg/dL and a 2-hour post-load value below 140 mg/dL. Higher values meet

1. GLUCOSE
TOLERANCE
TEST
BY DR RAIHAN MANNAN
JR-1, DEPTT. OF PHYSIOLOGY
JNMCH, AMU, ALIGARH

2. CONTENTS
 DEFINITION
 INDICATION FOR OGTT
 CONTRAINDICATION FOR OGTT
 PREPARATION OF THE PATIENT
 CONDUCTING THE GLUCOSE TOLERANCE TEST
 NORMAL VALUES AND INTERPRETATION
 DIAGNOSTIC CRITERIA FOR DM
 GESTATIONAL DM

3. DEFINITION
 Glucose tolerance means ability of body to utilise
glucose
 GTT is well 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 glycosuria

5. CONTRAINDICATION FOR
OGTT
 There is no indication for doing OGTT in a person with
confirmed diabetics mellitus
 GTT has no role 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
 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

7. PREPARATION OF THE
PATIENT(cont…)

8. hours1 2 3
0
50
100
150
200
250
300
350
Renal
threshold
Normal
person
Black Alimentary
glycouria
Yellow
Renal
Glycosuria
Purple Diabetes
mellitus
Orange
Plasmaglucose(mg/dl)

9. CONDUCTING THE
GLUCOSE TOLERANCE
TEST► AT ABOUT 8 am, a sample of blood is collected in the
fasting state, urine sample is also obtained
► Glucose load dose: the dose is 75 g anhydrous glucose
(82.5 g of glucose monohydrate) in 250-300 ml of water
 When the test is done in children, the glucose dose
is adjusted as 1.75 g/kg body weight
► Sample collection
► 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
► The dose should be drunk within 5 minutes

10. NORMAL VALUES AND
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 on
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

12. Results:
 Fasting plasma glucose should be below 110 mg/dL
► Fasting levels between 110 and 125 mg/dL are borderline
"impaired fasting glycaemia"
► Fasting levels repeatedly at or above 126 mg/dL are diagnostic
of diabetes.
 A 1 hour GTT (Glucose Tolerance Test) glucose level below
180 mg/dL is considered normal
 For a 2 hour GTT (Glucose Tolerance Test) with 75g intake
► glucose level below 140 mg/dL is normal
► Blood glucose between 140 mg/dL and 200 mg/dL indicate
"impaired glucose tolerance”
► Blood glucose levels above 200 mg/dL at 2 hours confirm a
diagnosis of diabetes

13. ACOG recommends a two-step procedure:
► First step is a 50g glucose dose over one hour
► If blood glucose level is more than 140 mg/dL, it is followed
by a 100 gram glucose dose over 3 hours
► The diagnosis of gestational diabetes is then defined by a
blood glucose level exceeding the cutoff value on at least
two intervals, with cutoffs as follows:
► Before glucose intake (fasting): 95 mg/dL
► 1 hour after drinking the glucose solution: 180 mg/dL
► 2 hours: 155 mg/dL
► 3 hours: 140 mg/dL
GESTATIONAL DM

14. THANK YOU…