An Oral Glucose Tolerance Test (OGTT) is a way to measure your body's ability to use glucose. Your pancreas (a gland located behind the stomach) makes a hormone called insulin, which helps your body use the glucose in your blood. If your pancreas does not make enough insulin or if your body is unable to use the insulin it makes, you may have a high blood glucose level. The test involves having your blood checked early in the morning and then drinking a special sugar beverage. After 2 hours you will have your blood tested again. Sometimes blood sugar levels are also drawn at other times such as one hour, three hours, or four hours after the glucose drink.
If the OGTT shows that your blood glucose levels are higher than normal, your doctor may tell you that you have "impaired glucose tolerance." This often means that you are at risk for developing diabetes. Rarely, diabetes is diagnosed after an OGTT. Diabetes is a chronic (long term) illness that can happen when your body does not make enough insulin, or when your body has difficulty using the insulin that it does make.
Before OGTT
Your doctor will most likely give you either a glucose drink to take home or a prescription to bring to your pharmacy (for the special glucose drink). Some tests are done in a doctor's office but most often the test is done in a lab at a hospital or clinic. The test takes several hours (most of it is waiting between blood tests) so you will need to clear your calendar for most of the morning of the test. If you need to fill a prescription, be sure to call your pharmacy ahead of time to check to see if they have the glucose drink in stock, as some pharmacies may not carry this item.
3 DAYS before the OGTT
Plan on eating three healthy meals and snacks for 3 days before the test. You do not need to buy anything "special" but you do need to make sure you have healthy foods to eat. Your meals should be balanced with plenty of carbohydrates. Foods containing carbohydrates include:
12 HOURS before the OGTT
DO NOT eat, smoke or do heavy exercise 12 hours before the test. (For example: If your test is scheduled for 8:00 AM - Do not eat, smoke or do heavy exercise after 8pm the night before). You may drink plain, NOT flavored water.
On the Morning of the Test
When you are ready to leave your home to have your test done, be sure to remember to bring:
- Your laboratory slips
- Your glucose drink
- A CD or MP3 player with head phones (to listen to music while you wait)
- Reading material/book/magazine
VERY IMPORTANT!!!!!!! DO NOT DRINK the glucose beverage until you arrive at the lab. The lab technician will tell you when to drink the glucose beverage.
At the Lab
- A fasting blood glucose test is done. This is a simple blood test that checks your blood sugar before you drink the glucose beverage.
- The lab technician will tell you to drink the glucose beverage. It will taste very sweet. It is important to drink the whole amount fairly quickly.
- After you finish drinking all of the glucose beverage, you will be asked to sit quietly until it is time (one to two hours) for your next blood test. You may read, listen to music, talk, or do another quiet activity while you're waiting.
VERY IMPORTANT!!!!!!! DO NOT EAT or DRINK anything except plain water while you are waiting.
- Once your tests are done and the lab technician gives you permission to leave, you may go about your normal daily activities. You can go back to school or work, eat, drink, and do the regular exercise that you normally do.
The lab will usually send your results to your doctor within a few days. You may already have a follow-up appointment scheduled or your doctor may call you to review your results and let you know if there are any concerns.
Source: girlshealth.gov
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