This document provides information about glucose tolerance tests (GTT), including the procedure, interpretation of results, and types of GTTs. It discusses how GTTs are used to evaluate a person's ability to metabolize glucose by measuring their blood glucose levels at intervals after a glucose load. A standard oral GTT involves fasting overnight, drinking a glucose solution, and having blood drawn over 2 hours to analyze glucose tolerance. Results are interpreted based on blood glucose thresholds at each time point. Variations include IV GTT for patients with malabsorption and mini GTT involving only two blood samples.

1. GLUCOSE TOLERANCE
TEST
MRS. SUDHA GAUTAM
ASSOCIATE PROFESSOR
K.D. COLLEGE OF NURSING & PARAMEDICAL
SCIENCES, MATHURA

2. INTRODUCTION
• The ability to utilize carbohydrates can be determined by Glucose
Tolerance Test (GTT)
• At first, fasting blood glucose is estimated.
• Then loading dose of glucose is given.
• The blood glucose levels are estimated at regular intervals after giving
the glucose load to the client.
• In cases of Insulin Deficiency, blood glucose levels get elevated due to
impaired glucose utilization.

3. A) DECREASED GLUCOSE TOLERANCE
• Non- utilization of carbohydrate load is observed in conditions causing
hyper-glycemia such as –
Diabetes Mellitus
Hyperactivity of anterior pituitary and adrenal cortex
Hyperthyroidism
Stress

4. B) INCREASED GLUCOSE TOLERANCE
• Increased carbohydrate tolerance is observed in conditions that lead to
hypo-glycemia such as –
Hypopituitarism
Hyperinsulinism
Hypothyroidism
Adrenal Cortical Hypofunction
Decreased gastro intestinal absorption like celiac disease.

5. INDICATIONS FOR GTT
• In asymptomatic persons with sustained or transient glycosuria.
• In clients with symptoms of Diabetes but glycosuria or hyperglycemia
is absent.
• Clients with family history but no symptoms or positive blood
findings.
• In persons 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. CONTRAINDICATIONS OF ORAL GTT
• In proven cases of diabetes mellitus the test is not required
• GTT is required in doubtful cases and is not recommended for follow
up of patients.
• The test should not be carried out in acutely ill patients.

7. PRECAUTIONS FOR GTT
• The patient is instructed to have a good carbohydrate diet for 2 – 3
days prior to the test.
• Further more a diet containing about 50 - 75 grams of carbohydrate
should be taken on the evening prior to the test.
• Patient is advised not to take drugs that may influence the blood
glucose levels for at least 2 days prior to the test.
• Patient should abstain from smoking during the test as it may
negatively impact the blood glucose levels.
• Strenuous exercises on the previous day is to be avoided and till the
day testing is done.

8. TYPES OF GLUCOSE TOLERANCE TEST
• Standard Oral Glucose Tolerance Test
• I/V Glucose Tolerance Test
• Mini Glucose Tolerance Test

9. A. PROCEDURE FOR ORAL GTT
• The diagnosis of diabetes can be made on the basis of individuals
response to the oral glucose load, commonly referred to as Oral
Glucose Tolerance Test.
• The test is conducted preferably in the morning (ideal 09:00 AM to
11:00 AM)
• A fasting blood sample is drawn and urine is collected.
• The patient is given 75 grams of glucose orally dissolved in about 300
ml of water and it is to be drunk in about 5 minutes.
• Blood and urine samples are collected at 30 minutes interval for at
least 2 hours.
• All blood samples are subjected to glucose estimation while urine
samples are qualitatively tested for glucose.

10. ORAL GTT RESULT/ INTERPRETATION

11. ORAL GTT RESULTS/ INTERPRETATION
Mg/ DL
AFTER
EATING
2- 3 HOURS
AFTER EATING
BLOOD GLUCOSE CHART
NORMAL
FASTING
80 - 100 170 - 200 120 - 140
IMPAIRED
GLUCOSE 101 - 125 190 - 230 140 - 160
DIABETIC 126 + 220 - 300 200 +

12. GRAPHICAL REPRESENTATION

13. B. I/V GLUCOSE TOLERANCE TEST
• This test is undertaken for patients with malabsorption disorders
(Celiac Disease or Enteropathies)
• In such cases glucose cannot be well absorbed
• The result of GTT becomes inconclusive.
• It is carried by giving 25 gm of glucose dissolved in 100 ml distilled
water as i/v injection within 5 minutes.
• Completion of infusion takes 0 time.
• Blood samples are taken at 10 minutes interval for the next hour.
• The peak value is reached within a few minutes and the value returns
to normal in 45- 60 minutes.

14. I/V GTT INTERPRETATION
• In normal individuals blood glucose level returns to normal within 60
minutes.
• In diabetes mellitus, decline is slow.
• The initial values are attained in 120 minutes

15. FACTORS AFFECTING GTT
a) Acute Infections
b) Liver Diseases
c) Hyperthyroidism – There is steep rise in the curve.
d) Hypothyroidism – A flat curve is obtained in hypothyroidism.
THYROID HORMONE increases the absorption of glucose from the gut.
e) Starvation

16. MINI OR MODERN GTT
• As per WHO recommendations in Mini GTT minimum 2 samples are
collected-
a. Fasting (Zero Hour)
b. 2 Hour Post glucose load
• Urine samples are also collected during the same time
• The diagnosis is made from the difference observed in the two results

17. MINI GTT TEST RESULT INTERPRETATION
TIME OF SAMPLE
COLLECTION
NORMAL PERSON CRITERIA FOR
DIAGNOSING
DIABETES
MELLITUS
CRITERIA FOR
DIAGNOSING IGT
FASTING <110 mg/dl
<(6.1 mmol/L)
>126 mg/dl
>(7.0 mmol/L)
110 – 126 mg/dl
2 hours after glucose
load
<140 mg/dl
<(7.8 mmol/L)
> 200 mg/dl 140 – 199 mg/dl

18. PRECAUTIONS 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,
contraceptives drugs, glucocorticoids, niacin and phenytoin should be
avoided on that day.
CRITERIA FOR DIAGNOSIS OF DIABETES MELLITUS
A random plasma glucose concentration ( > 200 mg/dl ) accompanied by
classic symptoms of DM ( polyuria, polydipsia, weight loss) is sufficient
for the diagnosis of DM.

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