Has your doctor prescribed a 'GTT' for you? Or maybe you've heard of someone in your family or a friend getting this test. Some people get a little scared when they hear this name. "What kind of test is this? Will it hurt? Is it a serious illness?" they think. But in reality, this is a simple test that is often used to check for diabetes. So, let's clear up all the questions you have about it today.
What is a Glucose Tolerance Test (GTT)?
Simply put, a GTT is a test that accurately measures your body's ability to use and store glucose, or 'sugar'. Doctors most often use this test to diagnose diabetes mellitus .
Think about it, the food we eat, especially carbohydrates like rice, bread, and potatoes, provide our bodies with the glucose they need for energy. This glucose is what gives our body cells energy like gasoline. Our blood carries this glucose throughout our bodies.
Our body has an amazing mechanism to keep our blood sugar levels at a certain level. The main one that helps with this is a hormone called insulin . This is produced by our pancreas. If there is a problem with using this glucose in some way, the blood sugar level can increase. We call it hyperglycemia . Sometimes the blood sugar level can also decrease, which is called hypoglycemia .
So what the GTT does is give you a specific amount of glucose and watch how your body responds to it for several hours.
When should a GTT be done?
There are several situations in which your doctor may order this test. The main ones are:
- Diabetes: Especially identify conditions like prediabetes, type 2 diabetes, or gestational diabetes.
- Insulin resistance: A condition in which the body's cells do not respond properly to insulin.
- Reactive hypoglycemia: Watch for abnormally low blood sugar levels shortly after eating.
- Acromegaly: Identify a condition caused by excessive production of growth hormone.
- Identify some rare carbohydrate metabolism disorders.
In particular, this test is often performed to detect gestational diabetes, a condition that can occur in mothers during pregnancy. It is a common test performed during pregnancy.
How should I prepare for this GTT test?
The doctor will clearly explain how you should prepare for this test. Following those instructions exactly is very important for accurate test results. Let's look at some of the things you should usually do.
| What to do | Description |
|---|---|
| Awareness about medication | Tell your doctor about all the medications you take, even vitamins. Some medications can affect the test results. You may be asked to stop taking them a few days before the test. |
| Eating normally | For three days before the test, you should eat as usual. You should get at least 150 grams of carbohydrates per day. That means eating your usual portion of rice, vegetables, and fruits as usual. |
| General activities | Avoid excessive exercise in the days before the test. Continue with your normal daily activities. |
| Fasting | You must not eat or drink anything for at least 8 hours before the test. It is okay to drink a little water. |
| During the test | Once the test begins, you cannot eat, drink (except water), or smoke anything until it is over. |
What happens during the test?
The GTT test is usually done in the morning. You will have to stay at the hospital or lab for a few hours until the test is finished, so it is a good idea to bring something like a book.
Let's see what happens during the most popular two-hour GTT:
1. First blood sample: First, some blood will be taken from you. This is to check your fasting blood glucose level.
2. Drink the glucose solution: You will then be given a sweet liquid to drink. This is made by dissolving about 75 grams of glucose in water. You will be asked to drink it all within 5 minutes. This may taste a little strange to some people. It is like a sugary orange drink. The amount of glucose given to children and pregnant women may vary.
3. Follow-up blood sample: Exactly two hours after drinking the liquid, another blood sample will be taken from you. Sometimes, the doctor may take blood samples several times, about every half hour, as needed.
Other types of GTT
- One-hour GTT: This is a test that is often used to screen pregnant women for diabetes. A 50-gram glucose drink is given and a blood sample is taken one hour later. This usually does not require fasting.
- Three-hour GTT: Blood samples are taken before drinking a glucose solution, and then hourly for three hours.
- GTT for Acromegaly: This does not measure blood sugar, but growth hormone (HGH) levels. It looks at whether that hormone decreases after drinking glucose.
What happens after the test? Are there any side effects?
Once the test is over, you can continue with your work as usual. You can also eat again. Since you won't be eating for several hours, it's a good idea to bring a small snack.
The GTT is a very safe test .
Some people may feel a little dizzy or nauseous after drinking the sugary liquid. But that's normal. Serious side effects are rare. There may be some bruising and soreness where the blood was drawn. But that will go away in a day or two.
How to understand the results of the GTT Report?
Your report will show your blood sugar level in mg/dL (milligrams per deciliter) for each blood test. The results of a two-hour GTT are usually interpreted as follows:
| Blood sugar level after 2 hours | Meaning |
|---|---|
| Less than 140 mg/dL | Normal - Your body controls glucose well. |
| Between 140 mg/dL and 199 mg/dL | Prediabetes - A risky condition. Diabetes can be prevented by making lifestyle changes. |
| 200 mg/dL or higher | Diabetes - Diabetes may be a diagnosis. |
The most important thing is, don't try to interpret these values on your own. It's essential to discuss the report with your doctor, as these values can change in conditions like gestational diabetes.
If the results are abnormal, what do you do next?
Don't worry if a value on the report is slightly different. A doctor won't decide that you have diabetes just because one GTT test result is abnormal.
Most of the time, your doctor will ask you to repeat the test another day, or they will do another test like an A1C to confirm. Whatever the case, your doctor will explain everything you need to know. Ask any questions or concerns you have at that time. Getting the right information is the first step to getting healthy.
Take-Home Message
- The Glucose Tolerance Test (GTT) is nothing to be afraid of. It's a normal, safe test that looks at how the body uses sugar.
- It is essential to follow the doctor's instructions (such as fasting) exactly before this test to obtain accurate results.
- During the test, you drink a sweet liquid and then give several blood samples over a period of several hours.
- Don't panic if the results are abnormal. A single test is rarely enough to make a diagnosis.
- Most importantly: Once you receive your test report, be sure to show it to your doctor and discuss it with him. Never make decisions alone.
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