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Prakash Mishra
GLUCOSE TOLERANCE TEST

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 Glucose tolerance means ability to the body to
utilize glucose in blood circulation.
 Glucose tolerance test : The measurement
of plasma glucose before and after a specific
amount of glucose given orally should provide a
standard method to evaluate individuals and
specific values for normal and disease.
GLUCOSE TOLERANCE TEST

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 This test is used to assist in the diagnosis of diabetes
mellitus (DM).
 It is also used in the evaluation of patients with
hypoglycemia.
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USES

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 The GT test may be used for the following condition:
 Patients with a family history of diabetes.
 Patients who are massively obese.
 Patients with a history of recurrent infections.
 Patients with delayed healing of wounds (especially
on the lower legs or feet).
 Women who have a history of stillbirths, premature
births, or large babies.
 Patients who have transient glycosuria or
hyperglycemia during pregnancy or following myocar
dial infarction (MI), surgery, or stress.
INDICATION OF GLUCOSE TOLERANCE
TEST
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a) In proven cases of diabetes mellitus the test is not
required.
b) GTT is required only in doubtful cases, it is not
recommended for follow up of patient.
c) Patients with serious concurrent infections or end
ocrine disorders, because glucose intolerance will
be observed even though these patients may not
be diabetic.
CONTRAINDICATIONS

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Dizziness, tremors, vomiting, sweating, or
fainting may occur during testing.
 If these symptoms occur, a blood specimen
is obtained, and measure the blood glucose.
 If the glucose level is too high, the test may
need to be stopped and insulin administered
.
POTENTIAL COMPLICATIONS
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 Smoking.
 Stress
 Exercise during the test can affect glucose levels.
 Fasting or reduced caloric intake before the GT test can
cause glucose intolerance.
 Drugs
INTERFERING FACTORS
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 Standard Oral glucose tolerance test
 I/V Glucose tolerance test
 Mini Glucose tolerance test
TYPE OF GLUCOSE TOLERANCE TEST
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 Explain the procedure to the patient.
 Educate the patient about the importance of having adequat
e food intake with adequate carbohydrates (150 g) for at
least 3 days before the test.
 Instruct the patient to fast for 12 hours before the test.
 Instruct the patient to discontinue drugs (including tobacco)
that could interfere with test results.
 Give the patient written instructions explaining the pretest
dietary requirements.
 Obtain the patient's weight to determine the appropriate
glucose loading dose (especially in children).
PATIENT PREPARATION
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 At about 8 a.m. the fasting blood and urine
samples are collected. These are called zero
samples.
 Administer the prescribed oral glucose
solution, usually 75 g of glucose for
non-pregnant patients or 100 g for pregnant
patients.
 The glucose dissolve in 300 ml of lemon
juice/water mixture within 5min after taking
sample .
PROCEDURE OF OGTT
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 In pediatric patients 1.75 g of glucose /kg body
weight is given.
 Instruct the patient to ingest the entire glucose
load.
 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.
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 Inform the patient that tobacco, and smoking are not
allowed.
 Collect a venous blood &urine sample at 30 min.
interval for upto 150 min.
 Glucose is estimated in all the blood samples.
 Urine is analyzed for the presence of glucose.
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LABORATORY PROFILE OF A NORMAL
PERSON AFTER GLUCOSE LOAD
Fasting 30 min. 60 min. 90 min. 120 min. 150 min.
Blood
Glucose
(mg/dl)
75 130 150 110 90 70
Urinary
Glucose
nil nil nil nil nil nil

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NORMAL GLUCOSE TOLERANCE CURVE
0
50
100
150
200
250
300
350
400
0 30 60 90 120 150
Glucoseconc.inmg/dl
Time of sample in min.
Glucose
conc.
 Fastingbloodglucose
(zerohour sample)is75mg/dl.
 Whichiswellwithinthenormal
range(normal60-100mg/dl).
 Thereisriseofbloodglucose after
glucose loadandthepeakvalueis
observedatIhour.

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 Normally there is a rapid insulin response to the ingestion
of a large oral glucose load.
 This response peaks in 30 to 60 minutes and returns to
normal in about 3 hours.
 Patients with an appropriate insulin response are able to
tolerate the dose quite easily, with only a minimal and
transient rise in plasma glucose levels within 1 to 2 hours
after ingestion.
 Glucose will not spill over into the urine in normal patients
.
NORMAL GLUCOSE TOLERANCE
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LABORATORY PROFILE OF A DIABETC
PATIENT AFTER GLUCOSE LOAD
Fasting 30 min. 60 min. 90 min. 120 min. 150 min.
Blood
Glucose
(mg/dl)
130 200 280 260 220 170
Urinary
Glucose
nil ++ ++ ++ ++ nil
Fasting 30 min. 60 min. 90 min. 120 min. 150 min.
Blood
Glucose
(mg/dl)
230 300 345 365 350 330
Urinary
Glucose
++ +++ +++ +++ +++ +++
Moderate Diabetic Curve
Severe Diabetic Curve

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DIABETIC CURVE
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0
50
100
150
200
250
300
350
400
0 30 60 90 120 150
Glucoseconc.inmg/dl
Time of sample in min.
severe diabetic
Renal thresold

18. Fasting 30 min 60 min 90 min 120 min 150 min 180 min
Blood
Glucose
(mg/dl)
90 130 150 140 120 100 90
Urinary
Glucose
nil + + + + ± nil
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LABORATRORY PROFILE OF A PATIENT
HAVING RENAL GLYCOSURIA

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 Blood glucose levels are within the normal limits
but urine glucose is positive.
 Glucose tolerance curve is normal.
 Thus glucose is found in some of the samples
depending upon the renal threshold.
 There is lowering of renal threshold due to renal
tubular defect in glucose absorption.
 GTT is also useful in the diagnosis of this inherited
renal tubular defect.
RENAL GLYCOSURIA
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 Early diabetes mellitus,
 Pregnancy,
 Renal disease,
 Heavy metal poisoning
 Deficiency of carrier protein (SGLT-2).
 Renal glycosuria can also be observed in
children of diabetic parents.
CAUSE OF RENAL GLYCOSURIA
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21. Fasting 30 min 60 min 90 min 120 min 150 min 180 min
Blood
Glucose
(mg/dl)
90 230 180 150 120 100 90
Urinary
Glucose
nil + + nil nil nil nil
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LABORATRORY PROFILE OF A PATIENT
HAVING LAG CURVE

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 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.
 This is due to an increased rate of glucose absorption from the gut
(sometimes in hyperthyroid).
 The increase in blood glucose is due to delay in insulin action.
(Insulin function lagging behind, hence called Lag Curve)
LAG CURVE
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 Hyperthyroidism
 Pregnancy
 After gastro-enterostomy
 Early diabetes mellitus
CAUSE OF LAG CURVE
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 Fasting blood is ≤80 mg/dl.
 All samples show low blood glucose.
 Urine glucose is negative.
 Flat curves are seen in patients with hypoactivity of
other endocrine organs, e.g. in hypopituitarism and
Addison’s disease, malabsorption.
FLAT CURVE
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25. This test is 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.
IV GLUCOSE TOLERANCE TEST
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26.  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 samples are taken at 10 minutes interval
for the next hour.
 The peak value is reached within a few minutes
and the value touches to near normal in 45-60 minutes.
PROCEDURE
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 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.
INTERPRETATION
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28.  As per current WHO recommendations, in the
 mini or modern glucose tolerance test, only two
 samples are collected,
 Fasting (zero hour) and 2 hour post glucose load.
 Urine samples are also collected during the same
 time.
 The diagnosis is made from the variations
 observed in these results.
MINI GTT
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Decrease Glucose Tolerance
 Diabetes mellitus (DM): This disease is defined by glucose
intolerance and hyperglycemia.
 Acute stress response
 Cushing syndrome
 Chronic renal failure
 Glucagonoma
 Acute pancreatitis
 Diuretic therapy
 Corticosteroid
 Myxedema
 After gastrectomy.
CLINICAL SIGNIFICANCE
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30. Increased Glucose Tolerance
 Increased carbohydrate tolerance is observed in
all conditions that cause hypoglycemia:-
 Hypopituitarism
 Hyperinsulinism
 Hypothyroidism
 Adrenal Cortical Hypofunction
GLUCOSE TOLERANCE
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