Diagnosis

Type 2 diabetes is usually diagnosed using the glycated hemoglobin (A1C) test. This blood test indicates your average blood sugar level for the past two to three months. Results are interpreted as follows:

• Below 5.7% is normal.
• 5.7% to 6.4% is diagnosed as prediabetes.
• 6.5% or higher on two separate tests indicates diabetes.

If the A1C test isn't available, or if you have certain conditions that interfere with an A1C test, your doctor may use the following tests to diagnose diabetes:

Random blood sugar test. Blood sugar values are expressed in milligrams of sugar per deciliter (mg/dL) or millimoles of sugar per liter (mmol/L) of blood. Regardless of when you last ate, a level of 200 mg/dL (11.1 mmol/L) or higher suggests diabetes, especially if you also have signs and symptoms of diabetes, such as frequent urination and extreme thirst.

Fasting blood sugar test. A blood sample is taken after an overnight fast. Results are interpreted as follows:

• Less than 100 mg/dL (5.6 mmol/L) is normal.
• 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is diagnosed as prediabetes.
• 126 mg/dL (7 mmol/L) or higher on two separate tests is diagnosed as diabetes.

Oral glucose tolerance test. This test is less commonly used than the others, except during pregnancy. You'll need to fast overnight and then drink a sugary liquid at the doctor's office. Blood sugar levels are tested periodically for the next two hours. Results are interpreted as follows:

• Less than 140 mg/dL (7.8 mmol/L) is normal.
• 140 to 199 mg/dL (7.8 mmol/L and 11.0 mmol/L) is diagnosed as prediabetes.
• 200 mg/dL (11.1 mmol/L) or higher after two hours suggests diabetes.

Screening. The American Diabetes Association recommends routine screening with diagnostic tests for type 2 diabetes in all adults age 45 or older and in the following groups:

• People younger than 45 who are overweight or obese and have one or more risk factors associated with diabetes
• Women who have had gestational diabetes
• People who have been diagnosed with prediabetes
• Children who are overweight or obese and who have a family history of type 2 diabetes or other risk factors

After a diagnosis

If you're diagnosed with diabetes, your doctor or health care provider may do other tests to distinguish between type 1 and type 2 diabetes — since the two conditions often require different treatments.

Your health care provider will repeat the test A1C levels at least two times a year and when there are any changes in treatment. Target A1C goals vary depending on your age and other factors. For most people, the American Diabetes Association recommends an A1C level below 7%.

You will also receive regular diagnostic tests to screen for complications of diabetes or comorbid conditions.