Oral Glucose Tolerance Test (OGTT) - Serum Glucose Levels Post-Challenge

An oral glucose tolerance test (OGTT) is a blood test that shows how well your body handles sugar. You drink a sweet liquid that contains a measured amount of glucose, and your blood sugar is checked at set times afterward to see how quickly your body clears the glucose from your bloodstream.

An Oral Glucose Tolerance Test (OGTT) involves drinking a sweet liquid containing glucose, followed by blood tests at set intervals to measure your blood sugar levels. This helps doctors evaluate your body’s ability to regulate glucose, which is important for diagnosing conditions like diabetes or gestational diabetes.

This test is commonly used to screen for or diagnose diabetes, prediabetes, and gestational diabetes, which can develop during pregnancy. Your doctor may order it if you have symptoms of high blood sugar, risk factors such as a family history of diabetes, or if a fasting blood sugar test showed a borderline result.

Your doctor may recommend this test if you have symptoms of high blood sugar (such as frequent urination, extreme thirst, or fatigue), a family history of diabetes, or if you’re pregnant. It’s also used to monitor blood sugar control in people with known diabetes.

First, a blood sample is taken to measure your fasting blood sugar level. You then drink a glucose solution, and additional blood samples are drawn at specific time intervals, often one and two hours later. This allows your provider to see how your blood sugar rises and falls in response to the glucose drink.

After drinking the glucose solution, blood samples are taken at baseline and then at 30-minute intervals for up to 2 hours. The test measures how your body responds to the sugar, helping identify whether your pancreas produces enough insulin to keep blood sugar stable.

Before the test, you will usually need to fast for at least 8 hours, drinking only water. In the days leading up to the test, eat your normal diet, since sudden changes can affect your results. Tell your provider about all medicines and supplements you take, because some can influence blood sugar. Plan to bring a snack to eat after your final blood sample is drawn.

On the day of the test, avoid eating or drinking anything except water for at least 8 hours before your appointment. Wear comfortable clothing and bring any medications you take regularly, as you may need to adjust timing or dosage temporarily.