Fasting blood sugar is a test that measures glucose levels in the blood following a minimum 8-hour fasting period, according to Lab Tests Online. This test is often used as a screening and diagnostic tool for prediabetes and Type 1 and Type 2 diabetes.
The blood glucose screening test is used for detecting hyperglycemia, which is high blood glucose, and hypoglycemia, which is low blood glucose, notes Lab Tests Online. Additionally, it can be used to screen for potential diabetes in those who are deemed at risk, even before symptoms of the disease are noticed. This is important because diabetics don't always exhibit symptoms of the disease, and complications can occur when treatment is not started soon enough.
Pregnant women are also screened for gestational diabetes using a glucose blood test between the 24th and 28th week. Generally, a two-step approach is used to screen for diabetes during pregnancy. This approach involves fasting for 8 hours or more, measuring glucose levels, drinking a glucose solution and testing levels at 1- and 2-hour marks. This is known as the oral glucose tolerance test, and it is recommended by the American Diabetes Association and the U.S. Preventive Services Task Force.