OGTT test stands for Oral Glucose Tolerance Test. It is a type of blood test that is commonly used for the diagnosis of diabetes mellitus and some other conditions. In this test, a fasting blood sample is taken first and then...
What is OGTT test?
OGTT test stands for Oral Glucose Tolerance Test. It is a type of blood test that is commonly used for the diagnosis of diabetes mellitus and some other conditions. In this test, a fasting blood sample is taken first and then a standard dose of glucose is given to the patient. Usually, 2-4 blood samples are taken depending upon the type of OGTT such as 2-hour OGTT or 3 Hour OGTT.
What is the difference between OGTT and GTT?
GTT (Glucose tolerance test) is also known as OGTT test. And both test means the same.
What are the uses of OGTT test?
OGTT is indicated for the diagnosis or monitoring of the following conditions:
- Diabetes
- Prediabetes
- Gestational diabetes
- Insulin resistance
- Reactive hypoglycemia
- Metabolic syndrome
- Acromegaly
- Beta cell dysfunction
- Impaired carbohydrate metabolism
- Borderline Fasting blood glucose (Between 100-126 mg/dl) but symptoms indicative of diabetes mellitus.
- H/o macrosomia (big baby >4kg)
- H/o excessive weight gain during pregnancy
- To rule out benign renal glucosuria
- Past history of miscarriage
- Past history of congenital malformations in baby.
How do I prepare for an OGTT blood test?
Follow these simple steps to prepare yourself for an OGTT test:
- Book an appointment: Fix an appointment in a blood testing lab.
- Fasting: 8-12 hours fasting is required for OGTT test. Usually an overnight fasting is done, and blood samples are taken in the morning.
- Food: There is no need to restrict your carbohydrate intake a night before the test. So, you can eat a normal diet weeks or days before the test.
- Medications: Intake of certain drugs affect the result of glucose tolerance test. You may ask your doctor about any drug modification before the test. Drugs that can alter your glucose tolerance test includes:
- Diuretics
- Oral contraceptives
- Anti-convulsant drugs
- Large doses of salicylates etc.
How is an OGTT test done?
The procedure of OGTT test includes the following steps:
- Fating blood sample is collected as a baseline.
- You will be given a standard dose of glucose solution to drink within minutes.
- Dose of glucose may be different depending upon the type of GTT such as 75 gram of oral glucose solution is usually given to adults as per the recommendations of WHO (world health organisations). However, a 50-gm glucose over 1 hour is used for pregnant women to screen for gestational diabetes mellitus. If its is found to be abnormal then a 100-gm glucose over 3 hours can be performed.
- After giving test dose, blood samples are collected at an interval of 30 minutes to 60 minutes.
- Report is available on the same day.
Can I drink water during OGTT test?
Yes, you can drink water during the procedure. However, you are not allowed to eat anything except the glucose solution provided to you during the test.
What are the side effects of OGTT test?
OGTT test is a safe procedure. However, some individuals may experience some side effects such as:
- Nausea
- Light headache
- Sweatiness
- Pain at injection site
- Hematoma due to multiple punctures to locate vein in those where veins are not easily assessable.
How much time taken for OGTT test?
Time taken for OGTT test depends upon the type of OGTT test. Given below table summarizes the type of OGTT test, dose of glucose administered to patient and time taken in different types of OGTT test.
Type
Oral Glucose administered
Time taken
75 gm over 2 hr OGTT
75 gm
2 hr
100 gm over 3 hr OGTT
100 gm
3 hr
What is the normal range for OGTT test?
Normal range
Pre-diabetes
Diabetes
Fasting
126 mg/dl
2 hr after glucose administration
200mg/dl
HbA1c
140 mg/dl, then a 100-gm glucose over 3hour is performed.
OGCT test in pregnancy report analysis?
50 gm over 1 hr OGCT (oral glucose challenge test) report analysis:
OCGT screening test
Normal/NGT
Abnormal/IGT
1 hr OGCT
