Glucose Tolerance Test, 3-hour



Quest Diagnostics Test Code: 10559

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 3 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


Customers should observe 10-12 of fasting prior to going into the lab. This test requires four blood draws. The first will be taken when you arrive at lab. You will then be given a glucose solution to drink. 3 subsequent collections will be taken at 1 hour intervals. You will be required to remain at the lab until the final collection is taken. The blood draws for this test can also be taken at half hour intervals if requested. Please note the business hours for your selected lab location when determining when to come to the lab. Once the collection process has begun you will be required to remain at the lab for 3 hours. Be aware if the lab takes a break for lunch and make sure to arrive more than 3 hours prior to this time.


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround for the Glucose Tolerance 3 Hour Test is typically 1-2 business days.