2. Introduction of Glucose Tolerance
test
A Glucose tolerance test (GTT) is a procedure that
determine whether a patient can use and store glucose
normally.
The test is usually use to test for diabetes mellitus, insulin
resistance, impaired pancreatic beta cell function, and
some times reactive hypoglycemia or rarer disorders of
carbohydrate metabolism.
This test version of the test, an oral glucose tolerance test
(OGTT) is standard dose of glucose is ingested by mouth ,
and blood levels are checked two hours later.
3. What is glucose tolerance test
The oral glucose tolerance test (OGTT) is a 2 hour
test. It checks blood glucose levels. It examines the
blood sugar before and 2 hours after you have had a
sweet drink. It how exactly your body processes sugar.
Other usual tests such as random blood sugar or
Hb1Ac test, glucose tolerance tests are usually
prescribed fro those who are pregnant.
4. Definition
The glucose tolerance test (GTT) is performed to
determine how your body responds to glucose . You
drink a glucose solution, and your blood is taken at
intervals to see how quickly the glucose is removed
from the blood.
5. Indication of glucose tolerance test
Patients with a family history of diabetes.
Patients with delayed healing of wounds ( specially on
the lower legs or feet)
Patients who have transient glycosuria or
hyperglycemia during pregnancy, myocardial infection,
surgery and stress.
Patients with or without symptoms of diabetes mellitus
showing one abnormal blood finding
in patients with neuropathies or retinopathies of
unknown origin.
In women with H/o having delivered large babies.
6. Contra indication of OGTT test
In proven case of diabetes mellitus the test is not
required.
GTT is required only in doubtful case, it is not
recommended for follow up of patient.
Patient with serious concurrent infections or end of
ocrine disorders, because glucose in tolerance will be
observed even though these patients may not be
diabets.
The test should not be carried out in acutely ill patients.
7. Precaution of patient during GTT test
Or patient preparation
The patient instructed to have good carbohydrate diet
for 3 days prior to the test.
Diet containing about 30-50gram of carbohydrate
should be taken on the evening prior to the test.
The patient should avoid drugs likely to influence the
blood glucose levels for at least 2 days prior to the test.
Patient should abstain from smoking during the test.
Strenuous exercise on the previous day is to be
avoided.
The exercise is also to be avoided on the same day
prior to the test.
8. Types of glucose tolerance test
1. Standard oral glucose tolerance test
2. I/V Glucose tolerance test
3. Mini Glucose tolerance test
9. Procedure of std. oral glucose tolerance
test
At about 8 am the fasting blood and urine samples are
collected. These are called zero samples.
A loading dose of 75g. Anhydrous glucose dissolved in
250-300 ml of lemon juice or water is given to the
patient
In children 1.75g of glucose /kg body weight is given.
Instruction the patients to ingest the entire glucose
load.
10. Procedure
Tell the patient that he or she cannot eat anything until
the test is completed.
However encourage the patient to drink water. No
other liquids should be taken during the testing period.
Inform the patient that tobacco , and smoking are not
allowed .
Collect a venous blood & urine sample at 30 min.
interval for 2 hours or up to 3 hours.
Glucose is estimated in all the blood samples.
Urine is analyzed for the presence of glucose.
11. Normal glucose tolerance curve
Time Fasting ½ hr 1 hr after
taking
glucose
1 ½ 2 hr 2 ½ hr
Blood sugar
( mg/dl)
75 130 140 100 65 70
Urine sugar -ve -ve -ve -ve -ve -ve
• Fasting blood glucose zero hour sample is 75mg/dl
•Which is well within the normal range 60- 100mg/dl
•There is rise of blood glucose after glucose load and the
peak value is observed at I hours. This is due to absorption
of glucose from the intestine
12. Normal glucose tolerance curve
Insulin is released upon increase of blood glucose
level. There is fall in blood glucose with time due to
glucose utilization promoted by insulin
The normal blood glucose level is achieved after 250
min.
13. The range of blood sugar levels in GTT seen in normal persons and
diabetic patients (WHO recommendation test dose 75 g glucose)
Normal Criteria for
diagnosing
diabetes mellitus
Normal in
pregnancy
Fasting <100mg/dl >140 mg/dl <115mg/dl
1 hr after glucose <160 mg/dl No definite level <190 mg/dl
2 hrs after glucode <140 mg/dl >200mg/dl <165 mg/dl
14. Diabetic patient after glucose load
Moderate diabetic curve
Fasting 30 min. 60 min 90 min. 120 min 150 min
Blood
glucose
140 200 280 260 220 170
Urinary
glucose
Nil ++ ++ ++ ++ nill
Fasting 30 min. 60 min 90 min. 120 min 150 min
Blood
glucose
230 300 345 365 350 330
Urinary
glucose
++ +++ +++ +++ +++ +++
Serve Diabetic curve
16. Diabetic curve of GTT
Fasting blood glucose is higher than normal
The highest value is attained at 1 hour to 1:30 hour
min.
The highest value exceeds the renal thershold.
Glucose is found in almost all the urine sample
The blood glucose level does not return to the fasting
level within 2 hr 30 min.
17. Abnormal glucose tolerance result
Renal glycosuria :-
Blood glucose level are within the normal limits but
urine glucose is positive.
Glucose tolerance curve normal.
Thus glucose is found in some of the samples
depending upon the renal threshold.
There is lowering or renal threshold due to renal
tubular defect in glucose absorption.
GTT is also useful in the diagnosis of this inherited
renal tubular defect.
18. Cause of renal glycosuria
Early diabetes mellitus
Pregnancy
Renal disease deficiency of carrier protein
Havey metal poisoning
Renal glycosuria can also be observe in children of
diabetic parents.
19. Lag curve
Fasting blood glucose normal
½ to 1 hr blood glucose crosses renal thershold.
1 ½ to 2 hr blood glucose normal.
½ to 1 hr urine glucose positive.
Example- increased glucose absorption from intestine and
after partial gastrctomy .
Cause of lag curve:
Hypothyroidism
Pregnancy
After gastro enterostomy
Early diabetes mellitus.
20. Flat curve
Fasting blood glucose <75mg/dl
All sample show low blood glucose
Urine glucose is negative.
Flat curve are seen in patients with hypo activity of
other endocrine. E.g. in hypopituitarism and addison
disease, malaabsrption.
21. Cause of lag curve
Hypothyroidism
Pregnancy
After gastro enterostomy
Early diabetes mellitus.
Flat curve
22. Gestational diabetic curve
Fasting blood glucose >150mg/dl
½ to 1hr blood glucose >190 mg/dl
1 ½ to2 hr blood glucose >165 mg/dl
½ to 1 hr urine glucose postive.
24. IV Glucose tolerance test
This test undertaken for patients with malabsorption.
Under these conditions oral glucose load is not well
absorbed and the results of oral glucose tolerance test
become inconclusive.
The values for the IV GT test differ slightly from those
of the oral GT test because IV glucose is absorbed
faster
25. Procedure
I/V glucose tolerance test is carried out by giving 25 g
of glucose dissolved in 100 ml intravenous injection
within 5 minutes.
Completion of infusion is taken as 0 time.
Blood sample are taken at 10 min. interval for the next
hour.
The peak value is reached within a few minutes and
the value touches to near normal in 45- 60 min.
26. Interpretation
In normal blood glucose level returns
Normal within 60 min.
In Diabetes mellitus , decline is slow
The initial values are attained in 120 min.
27. Mini GTT
As per current WHO recommendations, in the mini or
modern glucose tolerance test only two sample are
collected.
Fasting ( zero hour) and 2 hour post glucose load
Urine sample are also collected during the same tinme
The diagnosis is made from the variation .
Observed in these result.
28. Clinical Significant of GTT
Increase Glucose tolerance
Increase carbohydrate tolerance is observed in all condition
that cause hypoglycemia.
Hypopituitarism
Hyperinsulinism
Hypothyroidism
Adrenal Cortical Hypo function
