Doctors determine if a person has high blood glucose using a blood glucose test, which provides a measurement of sugar levels through a blood sample, according to MedlinePlus. Higher than normal blood glucose levels may indicate prediabetes, diabetes, uncontrolled diabetes or other health conditions, such as pancreatitis, pancreatic cancer or an overactive thyroid gland.
A fasting blood sugar test requires a person to abstain for eight hours, while a random blood sugar test may be performed any time, explains MedlinePlus. Doctors typically order the test to monitor diabetics or confirm diabetes in individuals showing signs of the disease. They also use the test to diagnose patients who experience seizures, fainting episodes, confusion, vision problems or frequent urination.
The normal results for people who undergo fasting blood glucose tests usually range from 70 to 100 milligrams per deciliter, states MedlinePlus. Levels ranging from 100 to 125 milligrams per deciliter indicate a type of prediabetes known as impaired fasting glucose, which contributes to a higher risk of developing type 2 diabetes. A blood sugar level of 126 milligrams per deciliter or above indicates diabetes.
For individuals who go through random blood sugar tests, normal levels are typically below 125 milligrams per deciliter, notes MedlinePlus. Diabetics generally have blood sugar levels above 200 milligrams per deciliter.