The glycemic index (GI) of a food is a measure of how a specific food with carbohydrates causes blood sugar to rise. It is given as a number compared to the effect on your blood sugar of eating either glucose (a type of sugar) or white bread.
You might have heard of a test called hemoglobin A1C. Maybe your doctor recommended that you get this test, or maybe you saw the results of an A1C test among your other most recent tests. It is related to your blood sugar levels, and is often used to test for or monitor prediabetes and diabetes.