A glucose test measures the amount of sugar, or glucose, in your blood, which is absorbed into your bloodstream after you eat carbohydrates. This test is often performed to screen for conditions like prediabetes, diabetes, or gestational diabetes during pregnancy. Proper dietary preparation before a glucose test is important for obtaining accurate results, as certain foods can significantly influence blood sugar levels.
Foods to Include Before Your Test
In the days leading up to a glucose test, a balanced diet helps maintain stable blood sugar levels. Lean proteins are a good choice as they minimally impact blood glucose, providing sustained energy without rapid spikes. Examples include chicken breast, fish, eggs, and lean cuts of beef.
Non-starchy vegetables are beneficial due to their low carbohydrate and high fiber content. Options like broccoli, spinach, green beans, and leafy greens do not significantly affect blood sugar. Incorporating healthy fats, such as those in avocados, nuts, and natural peanut butter, can also help regulate blood sugar by slowing glucose absorption.
For some glucose tests, particularly the 3-hour glucose tolerance test, consume a diet with at least 150 grams of carbohydrates daily for three days prior. This carbohydrate intake ensures your body’s usual glucose processing is active. Good sources include whole-grain toast, oatmeal, and fruits like berries and apples.
Foods to Avoid Before Your Test
Certain foods and beverages should be avoided before a glucose test to prevent skewed results. Sugary drinks, such as sodas, fruit juices, sweetened teas, and sports drinks, cause a rapid and significant increase in blood glucose levels, potentially leading to a false positive result. These beverages contain simple sugars quickly absorbed into the bloodstream.
Refined carbohydrates, including white bread, pastries, sugary cereals, pancakes, and donuts, should be avoided. These foods are quickly broken down into glucose, leading to sharp blood sugar spikes. Similarly, starchy foods like white rice and pasta are rapidly converted to sugar and should be limited.
Even some seemingly healthy options, such as excessive amounts of high-glycemic fruits like bananas, mangoes, and grapes, contain enough natural sugar to affect test results. Fried foods and heavily buttered dishes are discouraged, as their high-fat content can slow digestion and interfere with how your body processes the glucose solution given during the test.
Fasting and Other Key Preparations
For certain glucose tests, such as the fasting plasma glucose (FPG) test or the oral glucose tolerance test (OGTT), a fasting period is required. This means abstaining from all food and beverages, except plain water, for at least 8 to 12 hours before the test. The hours spent sleeping usually count towards this fasting period.
During the fasting period, avoid anything that could impact blood sugar levels. This includes coffee and tea, even black varieties, as caffeine can affect glucose readings. Chewing gum and smoking are prohibited during the fasting window because they can stimulate digestion or affect metabolic processes.
Regarding medications, consult with your doctor about any prescription or over-the-counter drugs you are taking. Some medications, such as salicylates, diuretics, certain anticonvulsants, and corticosteroids, can influence glucose utilization and may need to be temporarily discontinued before the test. Never stop taking medication without explicit medical advice.
Strenuous exercise should be avoided for at least 8 to 24 hours before the test, as physical activity can affect blood glucose levels. Remaining adequately hydrated with plain water during the fasting period is advisable, as it can make blood draws easier.