Blood sugar glucose fasting test is a common diagnostic test used to measure the level of glucose in the blood after fasting for 8 to 12 hours. The test is used to diagnose diabetes, pre-diabetes, and monitor glucose levels in individuals with diabetes. The test involves taking a blood sample, usually from a vein in the arm, and measuring the glucose level using a glucose meter or a laboratory test. Normal fasting glucose levels are typically between 70 and 100 milligrams per deciliter (mg/dL), while levels above 126 mg/dL suggest diabetes. The test is generally safe, but individuals with a history of low blood sugar levels, such as those with hypoglycemia or who are taking medication for diabetes, should take precautions and consult with their healthcare provider.