Oral Glucose Tolerance Test
Oral Glucose Tolerance Test (OGTT) is a laboratory test used to assess the body’s ability to metabolize glucose and diagnose carbohydrate metabolism disorders such as prediabetes and diabetes mellitus.
Test procedure:
- The patient provides a fasting blood sample to determine the baseline glucose level.
- Then the patient drinks a solution containing a specific amount of glucose (usually 75 g dissolved in water).
- Blood samples are taken again 1 and 2 hours after glucose intake to evaluate the body’s response to the glucose load.
Preparation for the test:
- Follow a diet containing at least 150 g of carbohydrates daily for 3 days before the test.
- Do not eat or drink anything except water for 10-14 hours before the test.
- Smoking, coffee, and physical activity are prohibited during the test.
Result interpretation:
- Diabetes mellitus is diagnosed if fasting glucose is ≥7.0 mmol/L and/or 2-hour glucose is ≥11.1 mmol/L.
- Impaired glucose tolerance is diagnosed if 2-hour glucose is between 7.8 and 11.0 mmol/L.
- Normal values indicate normal glucose metabolism.
Indications for testing:
- Suspected diabetes or prediabetes.
- Monitoring glucose metabolism during pregnancy (gestational diabetes).
- Assessment of carbohydrate metabolism disorders in various clinical conditions.
The test is generally well tolerated but may sometimes cause nausea, weakness, or dizziness.
Thus, the oral glucose tolerance test is an important diagnostic tool for early detection of diabetes and evaluation of carbohydrate metabolism.