A glucose tolerance test, also known as an oral glucose tolerance test (OGTT), is an important diagnostic tool used to identify diabetes or prediabetes.
It measures how well the body can process glucose, which is the body’s main source of energy.
The test typically begins with a fasting period of at least 8 hours. During this time, the person being tested should not eat or drink anything except water.
This is done to ensure that the person’s blood sugar levels are at their lowest possible level before the test begins.
How to prepare for oral glucose tolerance test?
To prepare for the test, it is important to:
- Fast for at least 8 hours before the test. You should not eat or drink anything except water during this time.
- Avoid alcohol and strenuous exercise 24 hours before the test.
- Inform your doctor of any medications you are taking, as some may affect the results of the test.
- Wear comfortable clothing and shoes to the test, as you will be asked to walk on a treadmill or stationary bike during the test.
- If you have any chronic conditions such as diabetes, high blood pressure, heart disease, or are pregnant, please let your doctor know before taking the test.
Oral glucose tolerance (OGTT) test procedure
It measures the body’s ability to process glucose, which is the body’s main source of energy. The procedure typically involves the following steps:
- Fasting: The person being tested will need to fast (not eat or drink anything except water) for at least 8 hours before the test.
- This is done to ensure that the person’s blood sugar levels are at their lowest possible level before the test begins.
- Glucose Loading: The person will then be given a sugary drink containing a specific amount of glucose, usually 75 or 100 grams. The individual must consume the glucose solution within 5 minutes.
- Blood sugar measurements: Blood sugar levels will then be measured at specific intervals, such as 30 minutes, 60 minutes, and 120 minutes after the glucose loading.
- The individual will need to sit still and should not eat or drink anything other than water during the test.
- Analysis of Results: The results of the OGTT will be analyzed by a healthcare professional to determine whether the individual has diabetes or prediabetes.
- The results will be used to calculate the individual’s glucose tolerance, which is the ability of the body to process glucose.
- A high glucose tolerance indicates that the body is able to process glucose normally, while a low glucose tolerance may indicate prediabetes or diabetes.
How to read the oral glucose tolerance test results?
For a fasting glucose test, normal results typically fall between 70 and 99 mg/dL (3.9 and 5.5 mmol/L).
NOTE: Results that are higher than this may indicate prediabetes or diabetes.
For an oral glucose tolerance test (OGTT), normal results typically fall within the following ranges:
- Fasting glucose: 70 to 99 mg/dL (3.9 to 5.5 mmol/L)
- 1 hour after drinking glucose solution: less than 140 mg/dL (7.8 mmol/L)
- 2 hours after drinking glucose solution: less than 120 mg/dL (6.7 mmol/L)
what is the difference between 1-hour ogtt and 3 hours ogtt?
A 1-hour oral glucose tolerance test (OGTT) measures your body’s ability to process glucose (sugar) in a shorter period, while a 3-hour OGTT measures your body’s ability to process glucose over a longer period.
The 3-hour OGTT typically includes a series of blood glucose measurements taken at different intervals (usually at 0, 1, 2, and 3 hours) after you drink a glucose solution.
Here is the video of the oral glucose tolerance test
This test is often used to diagnose gestational diabetes and to evaluate glucose metabolism disorders.