Glucose Tolerance Test: Procedure, During Pregnancy, and Risk Factors

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 tells your doctor how exactly your body processes sugar. Unlike other usual tests such as random blood sugar or Hb1Ac tests, glucose tolerance tests are usually prescribed for those who are pregnant. 

Why is The Glucose Tolerance Test Done?

Very often, an oral glucose tolerance test (OGTT) is done for diabetes and prediabetes, especially when gestational diabetes is a cause for concern. The glucose tolerance test may be done to test: 

• Hypoglycemia. It is reactive in nature
• A hormonal condition known as Acromegaly. It may cause excess growth
• Beta-cell function impairment
• Resistance to insulin

The Procedure of the Glucose Tolerance Test

An oral glucose tolerance test (OGTT) is done using the following steps:

• A lab technician will take a sample of blood from your fingertip, earlobe or vein.

• They will test this fasting blood sugar for the baseline amount of sugar in your blood.

• After this, you will be given a glucose solution to drink. Most of such solutions contain 75 grams of glucose.

• Thereafter, you are advised to sit down or lay for about an hour.

• After 1 hour, the technician takes another blood sample for testing

• They may take more blood samples after 2 hours and after 3 hours have passed since taking the glucose solution.

• The lab technician tests the samples thus obtained. They will be measured for the amount of glucose present in the blood at each time period.

• Between testing times, it is advised to the patient to not be too active and not to drink too much water. This is because excess movement and hydration can impact the concentration of glucose in the blood. It can in turn adversely affect the test results.

Preparation For Glucose Tolerance Test

It is advised not to take any meals at least 8 to 12 hours before this test. Then, the fasting blood sugar is tested. Your doctor may advise you not to take any medicines before the test. This is because it may affect the test results in an adverse manner. The patient is advised to keep their bodily movements to a minimum during the waiting period and not to hydrate themselves too much as it may affect the test results in effect.

What If Glucose Tolerance Test Results are Present/Absent?

Following are the normal and abnormal levels of blood glucose both for the normal population as well as those with gestational diabetes. These can be interpreted accordingly by an endocrinologist to prescribe the appropriate medicines such as Glycomet or Metformin as may be needed. These values are to be considered with caution as they may vary with respect to the diagnostic lab at which the glucose tolerance test is being done.

Normal Results for Type 1 Diabetes or Type 2 Diabetes

• Fasting glucose level: 60 to 100 mg/dL
• One-hour glucose level: < 200 mg/dL
• Two-hour glucose level: < 140 mg/dL

Impaired Results for Type 1 Diabetes or Type 2 Diabetes

• Fasting glucose level: 100 to 125 mg/dL
• Two-hour glucose level 140 to 200 mg/dL 

Abnormal (Diagnostic) Results for Type 1 Diabetes or Type 2 Diabetes

• Fasting glucose level: > 126 mg/dL
• Two-hour glucose level: > 200 mg/dL

Normal Results for Gestational Diabetes

• Fasting glucose level: < 90 mg/dL
• One-hour glucose level: < 130 to 140 mg/dL
• Two-hour glucose level: < 120 mg/dL

Abnormal Results for Gestational Diabetes

• Fasting glucose level: > 95 mg/dL
• One-hour glucose level : > 140 mg/dL
• Two-hour glucose level: > 120 mg/dL

Glucose Tolerance Test During Pregnancy

In India, owing to past research, women are at the most risk for developing gestational diabetes. Therefore, pregnant women are routinely checked for diabetes. Gestational diabetes does not cause evident symptoms. This makes testing all the more important.

If gestational diabetes is not identified and treated at the right time, it may risk your and the baby's health. During pregnancy, one's body has to pump out extra insulin to meet the growing baby's needs. In order to meet the extra demand of various growing body parts of the baby, insulin is mainly required to give the energy.

The gtt test in pregnancy is carried out when one is about 24 to 28 weeks pregnant. If one has had gestational diabetes before, the glucose tolerance test for pregnancy is done much earlier. This will be initially done between 16 and 18 weeks of pregnancy and then again between 24 and 28 weeks of the gestation term.

Risks Associated with Gestational Diabetes

It is seen that one is most likely to develop gestational diabetes if:

• You are obese or overweight. The higher the body mass index (BMI) the greater is seen to be one's risk
• If your previous baby had a birth weight of 4.5 kg or more.
• If you have had gestational diabetes before
• If you have had diabetes in your family, i.e., a parent, sibling or a child
• If your origin family had large cases of diabetes. It is known from research that South Asian, Middle Eastern or Caribbean descent people are at a much higher risk generally of developing diabetes.

What is The Cost of a Glucose Tolerance Test in India?

The average cost of a glucose tolerance test ranges from approximately Rs. 200 to Rs. 500.If you are pregnant and have a family history of diabetes, you are suggested to get the glucose tolerance test done to be on the safe side. Ultimately, we want a healthy mother and a healthy infant. As they say, prevention is better than cure. Hence, in order to prevent any growth abnormalities in the child, it is advised to get this test done at the best lab. Metropolis Healthcare is at your service 24/7 with state-of-the-art testing facilities. Book your test appointment today at: www.metropolisindia.com.