
A glucose tolerance test measures how well your body’s cells are able to absorb glucose, or sugar, after you ingest a given amount of sugar. Doctors use fasting blood sugar levels and hemoglobin A1c values to diagnose type 1 and type 2 diabetes, and prediabetes. A glucose tolerance test can also be used. Doctors primarily use a glucose tolerance test to diagnose gestational diabetes.
Doctors often diagnose type 1 diabetes quickly because it usually develops quickly and involves high blood sugar levels. Type 2 diabetes, on the other hand, often develops over years. Type 2 diabetes is the most common form of diabetes, and it usually develops during adulthood.
Gestational diabetes occurs when a pregnant woman who doesn’t have diabetes before pregnancy has high blood sugar levels as a result of the pregnancy. The American Diabetes Association estimates that gestational diabetes occurs in 9.2 percent of pregnancies.