Glucose in the blood - tests with overload: two-hour postprandial test and oral glucose tolerance test (GTT) - indications for investigation and contraindications, implementation of the tests, source of errors, reference ranges, results interpretation
Post prandial glucose tests: The postprandial glucose test is usually carried out two hours after the person consumes a meal high in carbohydrates. The purpose is to calculate the body's insulin reaction to carbohydrate ingestion, which peaks about two hours after the carbohydrate meal challenge. Requires consuming a balanced meal including at least 100g carbohydrates, followed by a blood sample collected two hours later.
Range for Post Prandial glucose test: A normal range blood sugar level 2 hr after eating is less than 7.8 mmol/L
Oral glucose tolerance test: A test to determine the body's ability to handle glucose. In the test, a person fasts overnight Then first, the fasting blood glucose is tested. After this test, the person receives 75 g of glucose. Blood samples are taken up to four times to measure the blood glucose. Screening of gestational diabetes in population of pregnant women the overload test is with 50 g of Oral Glucose.
Range for Oral Glucose tolerance test:
Sources of Errors: For the test to give reliable results, the person must be in good health (not have any other illnesses, not even a cold). Also, the person should be normally active and should not be taking medicines that could affect the blood glucose. The morning of the test, the person should not smoke or drink coffee. Taking a medicine - Drugs that can increase glucose measurements include the following: Birth control pills; Corticosteroids. Drugs that can decrease glucose measurements include the following: Acetaminophen; Alcohol
Indications: It’s recommend using a glucose tolerance test if the fasting blood glucose level measures are in the range of 5.6 mmol/L to 6.9 mmol/L. Used check for diabetes that occurs with pregnancy (gestational diabetes).
Result Interpretation: The outcome of the test may show:
- Normal glucose tolerance
- Depressed glucose tolerance - in which the blood glucose peaks sharply before declining slower than usual to normal levels - as in: Diabetes mellitus.
- Increased glucose tolerance in malabsorption syndrome, insulinoma