What is a Glucose tolerance test?

A lab test called the glucose tolerance test measures how quickly your body transports sugar from the blood to tissues like muscle and fat. The exam is frequently used to identify diabetes.

The tests used to screen for diabetes during pregnancy are same, but they are performed differently.

Why is the test done?

The sugar that the body utilizes as fuel is called glucose. Untreated diabetic patients have elevated blood glucose levels.

The following first tests are frequently used to identify diabetes in adults who are not pregnant:

  • If the fasting blood glucose level is more than 126 mg/dL (7 mmol/L) on two independent tests, diabetes is diagnosed.
  • Diabetes is identified if the hemoglobin A1c test result is 6.5% or above.

Diabetes can also be identified via glucose tolerance testing. When a person's fasting blood glucose level is high but not high enough (over 125 mg/dL or 7 mmol/L) to fulfill the diagnosis for diabetes, the OGTT is used to screen for or diagnose diabetes.

An early indication of diabetes than an abnormal fasting glucose is aberrant glucose tolerance, which occurs when blood sugar levels rise excessively following a glucose challenge.

How the test is administered

The oral glucose tolerance test is the most used type of glucose tolerance evaluation (OGTT).

Blood will be sampled before the test starts.

The next step will need you to consume a liquid containing a specific level of glucose (usually 75 grams). After the solution, your blood will be drawn again every 30 to 60 minutes.

The exam might last up to three hours.

The intravenous (IV) glucose tolerance test is a comparable examination (IGTT). Diabetes is seldom and hardly ever diagnosed using this method. In one variation of the IGTT, you receive a 3-minute glucose injection into a vein.

How to prepare for the exam

Following are the points to remember before the test:

  • Make sure you eat normally for some days before the test.
  • At least eight hours before the test, refrain from eating or drinking anything. You cannot eat while taking the exam.
  • If any of the medications you take have the potential to alter the outcome of the test, ask your doctor.

The Experience of the Test

The glucose solution is equivalent to a highly sweet drink when consumed.

It is extremely rare for this test to have serious negative effects. After consuming the glucose, some patients experience nausea, dizziness, lightheadedness, or even fainting symptoms during the blood test. If you have a history of these symptoms following blood tests or other medical procedures, let your healthcare professional know.

Is there any risk associated with the test?

No, there is no risk or danger of having a blood test. One might feel bruising or discomfort when the needle goes inside but it will disappear soon.

Understanding the results

Normal Results

Normal blood values for a 75-gram OGTT used to check for type 2 diabetes in those who are not pregnant:

Fasting - 60 to 100 mg/dL (3.3 to 5.5 mmol/L)

1 hour - Less than 200 mg/dL (11.1 mmol/L)

2 hours - This value is used to make the diagnosis of diabetes.

  • Less than 140 mg/dL (7.8 mmol/L) is normal.
  • Between 141 mg/dL and 200 mg/dL (7.8 to 11.1 mmol/L) is considered impaired glucose tolerance.
  • Above 200 mg/dl (11.1mmol/L) is diagnostic of diabetes.

The mentioned levels serve as standard benchmarks for these tests' outcomes. Different laboratories may have somewhat different normal value ranges. Several laboratories test various samples or use various metrics. Ask your physician what your particular test findings signify.

In pregnancy normal results

  • GTT Fasting: ≥92 mg/dL (5.1 mmol/L),
  • One hour: ≥180 mg/dL (10 mmol/L),
  • Two hour: ≥153 mg/dL (8.5 mmol/L)

Abnormal Results

If your blood glucose level is greater than usual, you may have diabetes or pre-diabetes:

  • Impaired glucose tolerance refers to a 2-hour result between 140 and 200 mg/dL (7.8 and 11.1 mmol/L). You are now more likely to eventually get diabetes or you are pre-diabetic.
  • Diagnosing diabetes requires a blood glucose level of 200 mg/dL (11.1 mmol/L) or greater.

Your blood glucose level may increase if your body experiences significant stress, such as that brought on by trauma, stroke, heart attack, or surgery. Your blood glucose level can be lowered by vigorous exercise.

Your blood sugar level can be increased or decreased by several medications. Inform your physician of any medications you are taking before the test.

Frequently Asked Questions

1. What is a glucose tolerance test?

A glucose tolerance test (GTT) evaluates the body's capacity to handle blood sugar (glucose). It involves monitoring the blood glucose levels before and after consuming a sweet beverage. This test's results can assist medical professionals in identifying type 2 diabetes or pre-diabetes (impaired glucose tolerance).

2. Why would a doctor prescribe tests for glucose tolerance?

A glucose tolerance test is prescribed to measure how quickly your body transports sugar from the blood to tissues like muscle and fat. The exam is frequently used to identify diabetes.

3. What is a normal glucose tolerance test result?

Glucose Tolerance Test: At 2 hours, a blood sugar level of 140 mg/dL or lower is considered normal, 140 to 199 mg/dL indicates you have prediabetes, and 200 mg/dL or higher indicates you have diabetes.

4. What is a 2 hour glucose tolerance test?

Test for Oral Glucose Tolerance (OGTT)-The OGTT is a two-hour test that measures your blood sugar levels before and after you consume a particular sweet beverage. It reveals to the physician how your body metabolizes sugar.

5. Can we drink water before the GTT test?

Yes, you can drink water before a GTT test.

6. How much time does the glucose tolerance test take?

For the glucose tolerance test, blood will be taken twice in 30 to 60 minutes after you drink the solution, hence the test might take up to 3 hours.

7. Does the glucose test affect the baby?

The glucose test is safe for pregnant women and does not affect the baby but make sure to inform your doctor if you are pregnant.

8. Why is a glucose tolerance test required during pregnancy?

A glucose tolerance test (GTT) is a blood examination to determine if you experienced excessive blood sugar levels or diabetes throughout pregnancy. If not addressed properly, this might lead to issues for both the mother and the child. Thus, testing is essential to ensure diagnosis.

9. What is the cost of a glucose tolerance test?

The average cost of GTT is between Rs. 300 to Rs. 800, which can vary from place to place.

10. Where can I get a glucose tolerance test in Hyderabad?

If you are looking for a glucose tolerance test in Hyderabad, then visit Medicover Hospitals.