Glucose Tolerance Test (OGTT)

What is a glucose tolerance test?

A glucose tolerance test, also known as an oral glucose tolerance test (OGTT), is used to detect or confirm diabetes. It is commonly used to screen for type 2 diabetes and gestational diabetes, a type of diabetes that develops in pregnant women.

How it works

The OGTT measures how your body responds to sugar. More specifically, glucose is the type of sugar that your body uses to supply energy to its cells. Your body breaks down the food that you eat into glucose, which then enters your bloodstream. A hormone called insulin helps bring the glucose from your bloodstream into the cells of your body.

If your body has difficulty responding to insulin, or if your body cannot produce enough insulin, the glucose levels in your blood will be too high. This can be a sign of pre-diabetes or diabetes. Diabetes is a serious medical condition that can damage organs and tissues in your body if uncontrolled.

Why do you need a glucose tolerance test?

You might need an OGTT if you:

  • Are overweight or obese
  • Have high blood pressure
  • Have a family history of diabetes
  • Have polycystic ovarian syndrome
  • Have high triglycerides, a type of fat in your blood
  • May have dumping syndrome, where food moves from your stomach into your small bowel too quickly
  • Had gestational diabetes during a previous pregnancy

The above are risk factors for diabetes and gestational diabetes. You may order an OGTT to screen and diagnose these 2 conditions.

What are the risks and complications of a glucose tolerance test?

The OGTT causes very few issues for patients who complete this test. Side effects, if any, are usually minor.

After your blood is drawn, you may experience:

  • Bruising or bleeding
  • Dizziness or lightheadedness.

After drinking the glucose drink, you may experience:

  • Bloating
  • Headache
  • Nausea
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