All About OGTT (Oral Glucose Tolerance Test)

All About OGTT (Oral Glucose Tolerance Test)

OGTT test or oral glucose tolerance test is useful to screen for prediabetes and type 2 diabetes. Moreover, this test includes consuming a product comprising glucose and then a blood draw. OGTT checks the amount of glucose it contains. 

What is OGTT?

These tests are for insulin resistance and type 2 diabetes mellitus. In addition, the test detects whether an individual may metabolize carbs and glucose. Also, OGTT shows whether a person suffers from the following conditions:

  • prediabetes
  • insulin resistance
  • gestational diabetes

How does OGTT work?

The test demands fasting for a minimum of eight hours. A doctor takes a blood sample. Then, an individual consumes a product comprising glucose. Consequently, a doctor takes another blood sample following two hours.

OGTT results show whether a person experiences prediabetes or diabetes. Below is a table indicating the OGTT results two hours after consuming a liquid comprising 75 g of glucose:

Normal140 mg/dl or less
Prediabetes140 to 199 mg/dl
Diabetes200 mg/dl or more

The GTT normal sugar level is below 140 mg/dL. Also, if the sugar level goes between 140 to 199 mg/dL, it indicates prediabetes. 

The OGTT normal sugar level for fasting are:

  • 100 to 125 mg/dL for prediabetes
  • 126 mg/dL or more for diabetes 
  • Above 92 mg/dL for gestational diabetes.

The OGTT normal sugar level for post-two hours are:

  • 140 to 199 mg/dL for prediabetes
  • 200 mg/dL or more for diabetes 
  • More than 153 mg/dL for gestational diabetes.

OGTT Types

The test process may differ significantly depending upon the test objectives. The amount of the oral glucose solution may vary with the number of blood draws and their timing as well. Even there are differences in which a low-carb meal might be advisable. Below are the 2 standard variations employed for diagnostic as well as screening means:

  • A 2-hour OGTT: consists of 2 blood draws. It is useful for diagnosing diabetes or prediabetes in non-pregnant adults and kids.
  • A 3-hour OGTT: consists of 4 blood draws. The test is helpful for screening for gestational diabetes.

Merits and demerits 

  • OGTT comes with the advantage of identifying early damage. This implies that prediabetic patients may often treat their health problems using diet and exercise instead of medications.
  • OGTT is far more sensitive in comparison to FPG or fasting plasma glucose test.
  • It is the only test useful for definitively diagnosing IGT or impaired glucose tolerance.
  • Doctors advise OGTT on suspecting diabetes, however, the FPG gives a standard result. 

Also, OGTT has its demerits as well. These are:

  • OGTT is a time-consuming procedure. It demands widespread pre-test fasting as well as long waiting and testing time. 
  • Factors like ailments, stress, and medicines may affect the test outcomes.
  • Blood stability post-collection is quite low. This implies that the outcomes may sometimes be twisted. This is due to inappropriate storage of samples or handling.
  • As far as accuracy is concerned, the OGTT comes with a sensitivity of 81-93%. And, this is far better in comparison to FGP. FGP test comes with a sensitivity of 45-54%.

People not suitable for OGTT

There are a few individuals who are not appropriate for an OGTT. They are people with:

  • signs of diabetes such as increased urination or increased thirst
  • fasting blood sugar level of more than 126 mg/dL
  • a recent surgical procedure
  • infection, trauma, or intense psychological stress
  • ketones in their urine (a condition known as ketonuria)

How is OGTT performed?

OGTT is done at a physician’s clinic, office, or lab. In this:

  • Healthcare providers would take a blood sample from an arm’s vein. This would help in checking a person’s initial blood sugar level.
  • Then, the patient would have water of glucose.
  • After that, a person would go for another blood sugar test for two hours.
  • The test is of short duration during pregnancy. A person would have a sweet liquid. Consequently, a person would go for a blood test one hour later.

Side effects of OGTT

The test comes with some problems. A few individuals experience minor side effects from a needle stick or from a sweet beverage. Ill effects because of the drink are:

  • Headache
  • Nausea
  • Vomiting
  • Low levels of blood glucose (in rare cases)
  • Bloating

Other likely issues that may crop up due to blood tests are:

  • Infection
  • Too much bleeding
  • Falling unconscious
  • Above one tries to locate a vein (this might hurt somewhat).

OGTT might show whether an individual is prediabetic or diabetic. Individuals require fasting prior to this OGTT test. Afterwards, the doctor would ask patients to consume a liquid comprising glucose. Then, they would take a blood test to check their levels of blood glucose. Although individuals fail to undergo an OGTT at home, there are numerous best glucometer India available to buy online. Yet, people must talk about their results with a healthcare provider. This helps in giving a better diagnosis and deliberating their treatment plans.

An early diagnosis may considerably lower one’s risk of diabetes complications and mortality!

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All About OGTT (Oral Glucose Tolerance Test)

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