Oral Glucose Tolerance Test (OGTT)

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Oral glucose tolerance test (OGTT) or Glucose Tolerance Test (GTT) is a test performed as a standard for diagnosing diabetes as well as metabolizing a standardized measured amount of glucose — which is the main energy source in your body. This is a common test, especially during pregnancy to diagnose gestational diabetes.

By definition, gestational diabetes is likely to develop during pregnancy. Usually, this condition only lasts until the delivery process is complete. In general, this test is performed at 24 to 28 weeks of pregnancy.

An oral glucose tolerance test not only detects gestational diabetes, it can also detect prediabetes and diabetes. This test is highly recommended for adults who are at risk of diabetes or who may have diabetes.

How Oral Glucose Tolerance Test (OGTT) Works

If you are planning to have an oral glucose tolerance test, there are several important things you should know about the procedure itself, including: 

  • Fasting

Before getting your oral glucose tolerance test, you should fast for at least 8 hours or more — but not more than 16 hours. Thus, you need to prepare yourself, especially if you are pregnant.

  • Laboratory Test

During the 2-hour process of the oral glucose tolerance test, your diabetes levels will be examined. Your healthcare provider will draw laboratory blood to measure your fasting blood sugar levels. Then, you will be asked to drink 8 ounces of glucose solution containing 75 grams of sugar.

  • Blood Sampling

Then, you will be asked to wait at the office for approximately 2 hours while waiting for your health care provider to take blood samples up to 4 times at different times after you consume sugar. This is done to measure the blood glucose.

Cost Estimation for Oral Glucose Tolerance Test (OGTT)

The total cost for the test will depend on the type of diabetes, such as a fasting glucose test, daily curve glucose test, HbA1c, insulin, and OGTT

No special preparation is required for fasting that will last for about 8-12 hours. You are allowed to only drink water. 

Unlike the case with the HbA1c (hemoglobin A1c) test, which is an exam to measure the levels of HbA1c or glycosylated hemoglobin.

For a more accurate calculation of the oral glucose tolerance test (OGGT), contact Smarter Health

Pre-Oral Glucose Tolerance Test (OGTT)

The first step before starting an oral glucose tolerance test is to ensure a regular diet for a few days before the test. When consulting your doctor, you should explain in detail if you are taking certain medications. It is intended so that your test results will not be affected by the medicines. 

Before the test, you will be asked to do your usual activities, including eating and drinking. Then as previously mentioned, you will also be asked to fast for 8 to 12 hours without being allowed to eat or drink. 

The next day, you will do the test in the morning. OGTT is usually done in the morning. Keep in mind that you should not smoke and consume caffeine. If you have followed your doctor’s instructions before taking the oral glucose tolerance test, then you are ready to move on to the next stage.

During Oral Glucose Tolerance Test (OGTT)

The following is a series of tests performed during the oral glucose tolerance test or OGTT:

  • First, your doctor will first take your blood as a sample. You should note that this is your fasting blood sugar —  which will be compared to in the next step of the test
  • After that, you will be given a sweet drink, such as a glucose solution of about 75 grams. You should drink this solution immediately before proceeding to the next stage.
  • After 1 to 2 hours, your healthcare provider will draw your blood for a second sample. This is the post-glucose solution for blood. In some cases, the blood sample will be taken up to 4 times

Post-Oral Glucose Tolerance Test (OGTT)

Fasting for a few hours, then doing a series of tests certainly affect your stamina — which could make you feel lightheaded. After completing the oral glucose tolerance test, you are advised to  eat and drink as usual. The goal is to restore the lost body fluids. 

Understanding Your Oral Glucose Tolerance Test (OGTT) Results 

To understand your OGTT results, here are some things that can lead to one of the following diagnoses:

  • Normal Response

A person may be considered to have a normal response when the glucose level after two hours is less than 140 mg / dL and all the numbers listed for 0-2 hours are less than 200 mg / dL..

  • Impaired Glucose Tolerance

A person may be considered to have impaired glucose tolerance if the glucose level during fasting is less than 126 mg / dL and the glucose level for two hours is 140-199 mg / dL. This condition is called prediabetes. People with impaired glucose tolerance have a higher risk of developing diabetes.

  • Diabetes

A person may be considered diabetic when the results of two diagnostic tests carried out on different days show high levels of blood glucose. This means that the level after two hours is greater than 200 mg / dL or the glucose level during fasting is greater than 126 mg / dL. Then the HbA1c level is 65% or more. This further strengthens the diagnosis of diabetes mellitus.

  • Diabetes During Pregnancy

A pregnant woman may be considered to have diabetes if her fasting glucose level is more than 92 mg / dL or a glucose level after two hours is greater than 153 mg / dL.

Side Effects of Oral Glucose Tolerance Test (OGTT)

OGTT is a safe for you and your baby (for pregnant women). Although OGTT does not have a significant risk of side effects, there are still some things that you must pay attention to.

Within one day, your healthcare provider will take several samples of your blood. You should watch out for signs of infection, such as redness and swelling around the puncture site. This infection is usually followed by symptoms of fever or even fainting from not eating all day. Thus, it is highly recommended to eat and drink again as usual after you complete the OGTT

Some people will experience the side effects of TTGO because glucose solutions are difficult to tolerate, especially people who have higher sugar levels. Here are some of the side effects that you might experience:

  • Nausea
  • Diarrhea
  • Constipation.
  • Stomach ache.

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