Glucose Tolerance Test, 2-hour



Quest Diagnostics Test Code: 23475

Glucose is a small sugar molecule that is used in all the cells in the body as the main energy source in metabolism and cellular functions. The brain and the nervous system can only use glucose and no other sources or molecules for energy, therefore, there needs to be a steady amount of glucose available in the blood for the brain. Testing the blood for glucose is primarily used for the diagnosis of glucose intolerance and diabetes and to monitor the blood glucose for people on treatment of diabetes. There are many different ways to test glucose levels. This test measure the glucose after fasting and then having a sample of glucose drink to see how the body’s response is to glucose 2 hours later.

This test is performed in following conditions such as:

• Sweating
• Palpitations
• Hunger
• Confusion
• Blurred vision
• Dizziness
• Fainting
• In serious cases, seizures and loss of consciousness

Also Known As: 3 Specimens OGTT


People taking this test should be active and eat a regular diet that includes at least 150 grams of carbohydrate daily for three days prior to the test. Fasting should be observed prior to collection for 8-14 hours. It is advised to discontinue, whenever possible, all nonessential medication that can affect glucose metabolism at least three days before testing. Please consult your doctor regarding any medications and how they may affect this test. The Glucose Tolerance Test is collected as 3 specimens, fasting, 1 hour and 2 hours after drinking a glucose solution at the lab. Please ensure to schedule at least 2 hours of time for your collection


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround for the Glucose Tolerance 2 Hour Test is typically 1-2 business days.