GTT Full Form

GTT stands for Glucose Tolerance Test. GTT is a measurement that is used to check how the body is responding to glucose post consuming a certain amount of sugar. GTT is also called OGTT( Oral Glucose Tolerance Test )and generally, this test is conducted during pregnancy to rule out gestational diabetes. The other variety of the test includes the IGTT( Intravenous Glucose Tolerance Test ). This is rarely used where the glucose is injected intravenously for 2-3 minutes.


GTT is a simple test that involves the collection of blood prior to the procedure being started, this is called fasting blood sugar. The sample of blood is collected after a period of fasting for 7-8 hours. Once the blood sample is collected, the patient is asked to consume a prescribed amount of glucose in the form of a sugary drink( usually 50-75 gms is given ). After the consumption of glucose, the patient is asked not to eat or drink anything for two hours. Post two hours again the blood sample is collected to check the amount of glucose in the blood.

In IGTT the glucose is injected in the veins for 3 minutes. Blood insulin levels are checked by collecting the blood sample before the injection and 2-3 minutes after the injection. The IGTT method is never adopted to check for Diabetes rather it is conducted only for research purposes.

Importance of GTT:

Irrespective of whether the individual is diabetic or not, a timely check of blood sugar levels is necessary to understand how far our body is able to tolerate the glucose we receive from our daily diet. The blood sugars rise slightly after we consume a meal, so our pancreas releases hormone insulin which helps in the metabolism of this sugar and convert it into energy that can be used by the cells of our body thus the blood sugar goes back to normal. 

When a person is diabetic this excess sugar is not properly metabolized because our pancreas fails to produce enough insulin that is required to break down the glucose into energy. As a result, the glucose starts accumulating in the blood damaging the blood vessels and other organs of the body. This increase in blood sugar is the main cause of Diabetes.

Diabetes is a progressive disorder which if not controlled might lead to various other problems like nerve damage, heart disease, kidney failure, glaucoma, etc.

GTT is an important test that can rule out any possibility of acquiring type-2 Diabetes.

When to Undergo GTT:

The medical practitioner recommends GTT  in the following conditions:

  1. If the individual has high blood pressure

  2. In case of obesity 

  3. If the patient is suffering from hormonal problems like Hypothyroid or Polycystic Ovarian Syndrome. 

  4. Any family history of diabetes.

  5. At the time of pregnancy if the baby weight is more in scans compared to the gestational weeks or any past history of gestational diabetes in previous pregnancies.

Side Effect of GTT and Result:

  • Few individuals might notice stomach ache, nausea, headache, vomiting.

  • Normal fasting blood sugar range should be around 70-90mg/dL

  • Postprandial blood sugar( PPBS )- 80-140mg/dL

  • While GTT is done the normal blood sugar would be below 140mg/dL.

  • If the result is between 140-200mg/dL then it is considered as pre-diabetic.

  • The patient is considered as Diabetic if the test result is above 200mg/dL.

  • The test result varies due to several factors like activity, exertion, stress, or any underlying illness.

  • If the test result is normal then there is no need to worry but if the test result indicates prediabetes then the physician will advise the patient to have certain lifestyle modifications. Weight Loss and having an active lifestyle with healthy food options will definitely prove to be helpful.

  • If the test result indicates Diabetes then the patient is asked to undergo a few more blood tests that include FBS, PPBS, Pancreatic profile, ‘A1C’, etc to confirm the diagnosis. 

FAQ (Frequently Asked Questions)

1. What are the Risks of Gestational Diabetes?

Ans:  Gestational Diabetes will increase the risk of preeclampsia, high blood pressure, excessive weight gain of mother and fetus, preterm delivery. It also increases the chances of the child developing Diabetes.

2. How Does Glucose Tolerance Test Work in Pregnancy?

Ans: During the test, the mother is asked to drink glucose in the form of a sugary drink. The blood is drawn post 2 hours of having this drink and the mother is asked not to have anything else in between until the blood is drawn. A high level of glucose in the blood indicates that the body is unable to properly synthesize the glucose. Thus confirming the diagnosis of Gestational Diabetes. In most cases Gestational Diabetes resolves soon after the delivery but there are chances that the female acquires Diabetes.