Various blood tests can be used to screen for diabetes, including:

• Random blood sugar test. A blood sample will be taken at a random time. Regardless of when you last ate, a random blood sugar level of 200 milligrams per deciliter (mg/dL) or higher suggests diabetes.

• Fasting blood sugar test. A blood sample will be taken after an overnight fast. A fasting blood sugar level between 70 and 100 mg/dL is normal. A fasting blood sugar level from 100 to 125 mg/dL is considered prediabetes, which indicates a high risk of developing diabetes. If it's 126 mg/dL or higher on two separate tests, you'll be diagnosed with diabetes.

If you're diagnosed with diabetes, your doctor may do other tests to distinguish between type 1 and type 2 diabetes.

 Type 1 diabetes might be suspected if you have little or no ability to produce insulin, you have antibodies to insulin-producing cells in your blood, or you have toxic acids produced by the breakdown of fat (ketones) in your urine.

 Glycated hemoglobin (A1C) test. This blood test indicates your average blood sugar level for the past two to three months. It works by measuring the percentage of blood sugar attached to hemoglobin, the oxygen-carrying protein in red blood cells. The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached. Generally, a target A1C result is 7 percent or less.