The glucose tolerance test is a lab test to inspect how your body breaks down sugar. The test also known as Oral glucose tolerance test – non-pregnant; OGTT – non-pregnant; Diabetes – glucose tolerance test; Diabetic – glucose tolerance test.
Tests to evaluate for diabetes during pregnancy are done differently.
Glucose tolerance test during pregnancy described here.
How Glucose Tolerance Test is Performed
The most common glucose tolerance test is the oral glucose tolerance test (OGTT).
Before the test begins, a sample of blood will be taken.
You will then be asked to drink a liquid containing a certain quantity of glucose (normally 75 grams). Your blood will be taken once again every 30 to 60 minutes after you drink the service.
The test may use up to 3 hours.
A comparable test is the intravenous (IV) glucose tolerance test (IGTT). It is rarely used, and is never used to identify diabetes. With IGTT, glucose is injected into your vein for 3 minutes. Blood insulin levels are determined before the injection, and again at 1 and 3 minutes after the injection. The timing may differ.
How to Prepare for Glucose Tolerance Test
Make sure you eat usually for several days before the test.
DO NOT eat or drink anything for a minimum of 8 hours prior to the test. You can not eat during the test.
Ask your healthcare service provider if any of the medicines you take can affect the test results.
How the Test will Feel
Consuming the glucose option resembles drinking very sweet soda.
Severe side effects from this test are really unusual. With the blood test, some individuals feel nauseated, sweaty, lightheaded, or might even feel short of breath or faint after consuming the glucose. Inform your doctor if you have a history of these symptoms related to blood tests or medical treatments.
When the needle is inserted to draw blood, some people feel moderate pain. Others feel just a prick or stinging. Later, there may be some throbbing or a small contusion. This quickly disappears.
Why Glucose Tolerance Test is Performed
Glucose is the sugar the body uses for energy. People with unattended diabetes have high blood glucose levels.
Frequently, the first tests used to diagnose diabetes in individuals who are not pregnant are:
- Fasting blood glucose level: diabetes is diagnosed if it is greater than 126 mg/dL (7 mmol/L) on 2 various tests
- Hemoglobin A1c test: diabetes is diagnosed if the test outcome is 6.5% or greater
Glucose tolerance tests are likewise used to identify diabetes. The OGTT is used to evaluate for, or identify diabetes in individuals with a fasting blood glucose level that is high, but is low enough (above 125 mg/dL or 7 mmol/L) to meet the diagnosis for diabetes.
Normal Results for non-pregnant Glucose Tolerance Test
Normal blood worths for a 75 gram OGTT used to check for type 2 diabetes in those who are not pregnant:
- Fasting: 60 to 100 mg/dL (3.3 to 5.5 mmol/L).
- 1 hour: less than 200 mg/dL (11.1 mmol/L).
- 2 hours: less than 140 mg/dL (7.8 mmol/L).
The examples above prevail measurements for outcomes of these tests. Normal value varieties might differ a little among various laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the significance of your specific test results.
Your doctor will use the following values in milligrams/deciliter (mg/dL) to diagnose diabetes in a 75-gram OGTT:
Table Describes Results for 1 Hour and 2 Hour Glucose Tolerance Test
| When blood is drawn | For prediabetes | For diabetes | For gestational diabetes |
| Fasting | 100-125 mg/dL | 126 mg/dL or greater | greater than 92 mg/dL |
| After 1 hour | greater than 180 mg/dL | ||
| After 2 hours | 140-199 mg/dL | 200 mg/dL or greater | greater than 153 mg/dL |
Only one value needs to be elevated to be diagnostic for diabetes or gestational diabetes.
What Abnormal Results of Glucose Tolerance Test Mean
A glucose level that is higher than regular might suggest you have pre-diabetes or diabetes:
- A 2 hour value in between 140 and 200 mg/dL (7.8 and 11.1 mmol/L) is called impaired glucose tolerance. Your doctor might call this “pre-diabetes.” It implies you are at increased risk of developing diabetes gradually.
- A glucose level of 200 mg/dL (11.1 mmol/L) or greater is used to detect diabetes.
Severe stress to the body, such as from trauma, stroke, cardiac arrest, or surgery, can raise your blood sugar level. Energetic exercise can decrease your blood glucose level.
Some medicines can raise or decrease your blood sugar level. Before having the test, inform your provider about any medicines you are taking.
Risks Related the Test
You may have some of the symptoms listed above under the heading titled “How the Test will Feel.”.
Veins and arteries vary in size from one person to another and from one side of the body to the other. Getting a blood sample from some individuals might be harder than from others.
Other threats associated with having blood drawn are small, however might consist of:
- Excessive bleeding.
- Passing out or feeling lightheaded.
- Hematoma (blood building up under the skin).
- Infection (a minor risk any time the skin is broken).
