A glucose tolerance test measures how your body processes sugar, specifically glucose, and is often used to check for prediabetes, diabetes, or gestational diabetes during pregnancy. This test helps healthcare providers understand how efficiently your body’s cells absorb glucose after you consume a sugary drink. Proper dietary preparation is important for accurate results.
The Night Before Your Test
Careful preparation for your glucose tolerance test begins the evening before. You will be instructed to start an overnight fast, meaning no food or drink other than water for 8 to 12 hours before your test.
Prior to this fasting period, eat a balanced meal. Some healthcare providers recommend a diet rich in carbohydrates for three days leading up to the test, consuming around 150-200 grams of carbohydrates daily. This can include starchy foods like breads, cereals, pasta, rice, and potatoes. Avoid excessive amounts of sugary drinks, desserts, or large quantities of refined carbohydrates immediately before the fast.
Morning of the Test: Fasting and Water
On the morning of your glucose tolerance test, you must not consume any food or caloric beverages such as coffee, tea, juice, milk, or soda. Chewing gum, smoking, or eating cough drops and hard candy are also not permitted, as these can affect your blood sugar levels.
Plain water is the only liquid allowed during the fasting period and throughout the test. Staying hydrated is important for your comfort and can help prevent lightheadedness. If you take regular medications, discuss with your doctor whether you can take them with water on the morning of the test, as some medications might need to be delayed until after the test is completed. Over-the-counter medications, vitamins, or aspirin should be avoided for about 12 hours before the test.
After the Glucose Drink
Once you arrive for your test, a fasting blood sample will be taken. Following this, you will be given a glucose solution to drink, which typically contains 50, 75, or 100 grams of sugar, depending on the type of test being administered. Drink this entire solution within five minutes.
After consuming the glucose drink, you will enter an observation period, which can last from one to three hours with multiple blood draws at specific intervals (e.g., one, two, and three hours after the drink). During this time, it is important not to eat or drink anything else, besides sips of plain water if permitted by the medical staff, to avoid skewing the test results. Remaining seated and avoiding strenuous exercise is also advised, as physical activity can influence blood sugar levels and potentially impact the accuracy of the test.
Post-Test Recovery Eating
After your final blood draw, you can resume normal eating and drinking. It is often recommended to consume a balanced meal soon after the test to help stabilize your blood sugar levels, which may have fluctuated due to the fasting and the glucose load. This can help alleviate potential discomforts such as nausea, lightheadedness, or jitters.
Focus on foods that provide sustained energy and help regulate blood sugar rather than causing another rapid spike. Incorporating protein, fiber, and complex carbohydrates is beneficial. Examples include lean proteins like chicken or fish, fiber-rich vegetables, and whole grains. Avoiding immediate consumption of sugary snacks, highly refined carbohydrates, or heavy, greasy foods is often suggested, as these can lead to further blood sugar imbalances and discomfort.