Glucose tolerance tests are also used to diagnose diabetes. The OGTT is used to screen for or diagnose diabetes in people with a fasting blood glucose level that is high, but is not high enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.

1. Glucose Tolerance Test
Mr. Abhijit Bhoyar
Assistant Professor
Department of
Child Health
Nursing
Part-I
Glucose Tolerance Test
Mr. Abhijit Bhoyar
Assistant Professor
Department of
Child Health
Nursing
Part-I

2. Specific Learning Objectives
At the end of the lecture, the students will be
able to
• Define Glucose Tolerance Test.(GTT).
• Explain the decreased and increase glucose tolerance.
• Define Glucose Tolerance Test.(GTT).
• Enumerate indications of Glucose Tolerance
Test.(GTT).

3. Cont.…..
• Enlist Contraindications of Glucose Tolerance Test.(GTT).
• Identify the factors affecting Glucose Tolerance Test
(GTT).
• Describe the preparation for Glucose Tolerance
Test.(GTT).
• Explain the procedure of Glucose Tolerance Test.(GTT).
• Explain the Glucose Tolerance Test curve and its types.

4. Introduction
• The ability to utilize carbohydrates can be
determined by Glucose tolerance test.
• Initially fasting blood glucose is estimated
• A loading dose of glucose is given.
• The blood glucose levels are estimated at regular
intervals after the glucose load.
• In conditions of insulin deficiency, blood glucose
levels get elevated due to impaired utilization of
glucose.

5. Decreased Glucose tolerance
• Decreased carbohydrate tolerance (non-utilization
of carbohydrate load) is observed in conditions
causing hyperglycemia,
• for example: Diabetes mellitus, Hyperactivity of
anterior pituitary and adrenal cortex, Hyperthyroidism
and Stress.

6. Increased Glucose Tolerance
• Increased carbohydrate tolerance is observed in all
conditions that cause hypoglycemia-
Hypopituitarism
Hyperinsulinism
Hypothyroidism
Adrenal cortical hypofunction
Decreased gastro intestinal absorption like sprue
celiac disease.

7. Glucose tolerance test
Glucose tolerance means the ability
of the body to utilize glucose in blood circulation.
The glucose tolerance test, also known as the oral
glucose tolerance test, measures body's response to
sugar (glucose).
• The glucose tolerance test can be used to screen for
type 2 diabetes.

8. Indication of Glucose tolerance test
In asymptomatic persons with sustained or transient glycosuria.
In persons with symptoms of diabetes but no glycosuria or hyperglycemia.
Persons with family history but no symptoms or positive blood findings.
In persons with or without symptoms of diabetes mellitus showing one
abnormal blood findings.
In patients with neuropathies or retinopathies of unknown origin.
In women with H/o having delivered large babies.

9. Contraindications of glucose tolerance test
• In proven cases of diabetes mellitus the test is not
required.
• GTT is required only in doubtful cases, it is not
recommended for follow up of patient.
• The test should not be carried out in acutely ill
patients.

10. Factors affecting GTT
a) Acute infections- Cortisol is secreted, the curve is
elevated and prolonged.
b) Hypothyroidism- A flat curve is obtained in
hypothyroidism.
c) Thyroid hormone increases the absorption of
glucose from the gut.
d) Starvation- There is rise of counter regulatory
hormones, which show increased glucose
tolerance.

11. Some more Precaution Before GTT
• For proper evaluation of the test, the subjects should
be normally active and free from acute illness.
• Medications that may impair glucose tolerance
include diuretics, contraceptive drugs,
glucocorticoids, niacin, and phenytoin should be
avoided on that day.

12. Types of glucose tolerance test
Standard Oral
glucose
tolerance test
Intra Venous
Glucose
tolerance test
Mini Glucose
tolerance test

13. Preparation of Patient
• Patient should on carbohydrate rich unrestricted diet for 3
days.
• Patient should be ambulatory with normal physical
activity.
• Medications should be discontinued on the day of
testing.
• Exercise, smoking and tea or coffee are not allowed
during test period.
• OGTT carried out in the morning after patient has fasted
overnight for 8-14 hours.

14. Cont.….
• A fasting venous blood sample is collected in the
morning.
• Patients ingest 75 g of anhydrous glucose in 250-
300 ml of water over 5 minutes. ( for children, the
dose is 1.75 g of glucose per kg).

15. Cont…
• In the classical procedures, the blood and urine
samples are collected at half hourly interval of the
next three hours.
• A curve is plotted with the blood glucose levels on
the vertical axis against the time of collection on
the horizontal axis.
• The curve so obtained is called glucose tolerance
curve.

18. Procedure of Standard Oral glucose
tolerance test
• At about 8 a.m. the fasting blood and urine samples
are collected. These are called zero samples.
• A loading dose of 75 g. anhydrous glucose dissolved
in 250-300 ml of water is given to the patient.

19. Cont.….
• In children 1.75 g of glucose /kg body weight is
given.
• In the classical procedures, the blood and urine
samples are collected at half hourly interval of the
next two and a half hour or three hours.
• Glucose is estimated in all the blood samples.
• Urine is analyzed for the presence of glucose.

20. Glucose tolerance curve
• A curve is plotted with the blood glucose levels on
the vertical axis against the time of collection on
the horizontal axis.
• The curve so obtained is called glucose tolerance
curve.

24. 1. Normal Glucose Tolerance Curve
i) Fasting blood glucose (Zero hour sample)- is 90
mg /dl, which is well within the normal
range(Normal 60-100 mg/dl).
ii) There is rise of blood glucose after glucose load
and the peak value is observed at I hour. This is
due to absorption of glucose from the intestine.

25. Cont.….
iii) Insulin is released upon increase of blood glucose
level. There is fall in blood glucose with time due to
glucose utilization promoted by insulin.
iv) The normal blood glucose level is achieved after
150 minutes.

26. Cont….
A typical normal response shows following features.
• Initial fasting glucose within normal limits.
• The highest peak value is reached within 1 hour.
• The highest value does not exceed the renal
threshold (160-180 mg/dl).
• The fasting level is again reached by 2-2.5 hours.
• No glucose or ketone bodies are detected in any
specimen of urine.

27. 2. Diabetic Curve
• Fasting blood glucose is higher than normal
• The highest value is attained at 1 hour to 1 hour 30
minutes.
• The highest value exceeds the renal threshold
• Glucose is found in almost all the urine samples.
• The blood glucose level does not return to the
fasting level even within 2hour 30 minutes.

28. Response of diabetic patients
• Fasting blood glucose is definitely raised above 110
mg/dl.
• The highest value is reached after 1-1.5 hours.
• The highest value exceeds the renal threshold.
• The blood glucose level does not return to fasting level
within 2.5 hours. This is the most characteristic feature
of DM.
• Urine sample always contains glucose except in some
chronic diabetes or nephritis who may have raised renal
threshold.

30. Cont….
According to severity, GTC may be:
a) Mildely dibetic curve
b) Moderately severe diabetic curve
c) Severe diabetic curve

34. 3. Lag Curve
• Fasting blood glucose is normal.
• Sharp rise within 30 minutes to one hour
• The blood glucose levels exceed the renal
threshold.
• The decline is rapid and the normal levels are
attained back.
• Some of the urine samples contain glucose, where
the blood glucose is above the renal threshold.

35. Cause of Lag Curve
• Hyperthyroidism
• Pregnancy
• After gastro-enterostomy
• Early diabetes mellitus

36. 4. Curve for Renal Glucosuria
• Glucose appears in the urine at levels of blood
glucose much below renal threshold.
• Patients who show no glucosuria when fasting may
have glucosuria when blood glucose is raised.
It may be seen in :
• Renal disease and pregnancy
• Early diabetes

37. Expected Questions
Short
• Explain the decreased and increase glucose tolerance.
• Enumerate indications and contraindications of Glucose
Tolerance Test (GTT).
• Describe the procedure of Glucose Tolerance Test.(GTT).
Very Short
• Define Glucose Tolerance Test.(GTT).

38. References
1. Jacob Anthikad, Biochemistry for nurses 3rd ed.
2. Pankaja Naik, Essentials of Biochemistry, 1st ed.
3. Satyanarayan, Essentials of Biochemistry, 2nd ed.
4. A. C. Deb, Biochemistry, 4th ed.

39. THANK YOU