Type 2 Diabetes Diagnosis

Several blood sugar tests are ordered when a person's symptoms suggest diabetes or pre-diabetes. Diabetes screening tests are also ordered for people without symptoms who are at high risk of developing diabetes, such as people with a family history of diabetes, people who are obese, or people over 45 years old.

The values of the following tests may vary for different laboratories.

Blood Glucose Tests

Blood sugar levels normally increase after meals and decrease until the next meal. When the body is resistant to insulin or doesn't produce enough insulin, people develop high blood sugar (hyperglycemia). The normal range for blood sugar levels:

• Before meals is 70 to 99 mg/dL (milligrams per deciliter).
• After meals is less than 140 mg/dL

The pre-diabetes range for blood sugar levels:

• Before meals is 100 to 125 mg/dL (milligrams per deciliter).
• After meals is less than 140 to 200 mg/dL

The diabetes range for blood sugar levels:

• Before meals is over 126 mg/dL (milligrams per deciliter).
• After meals is over 200 mg/dL

Fasting blood glucose test

The fasting test results are:

• Normal = 99 mg/dL and below
• Pre-diabetes = 100 to 125 mg/dL
• Diabetes = 126 mg/dL (Confirmed by repeating the test on a different day.)

Oral glucose tolerance test

The test is used to diagnose diabetes or pre-diabetes. The oral glucose tolerance test is more sensitive than the fasting blood glucose test for diagnosing pre-diabetes.

Test results at the start of the test are the same as those listed for the fasting blood glucose test. The test results two hours after the glucose drink are:

Normal = 139 mg/dL and below
Pre-diabetes = 140 to 199 mg/dL
Diabetes = 200 mg/dL and above (Confirmed by repeating the test on a different day.)

Random (non-fasting) blood glucose test

A random blood glucose level of 200 mg/dL or greater in addition to the following diabetes symptoms is used to diagnose diabetes but not pre-diabetes:

• Increased thirst
• Frequent urination
• Unexplained weight loss

A positive diagnosis is confirmed by a fasting blood glucose or oral glucose tolerance test on another day.

Additional Tests

The following tests are given to:

• Differentiate between type 1 and type 2 diabetes.
• Monitor blood glucose levels.
• Diagnose diabetes complications.
• Diagnose pancreatic tumors.

C-peptide test

Hemoglobin A1C test

For people newly diagnosed with diabetes, the test determines how long they have been been experiencing high blood sugar levels. For people with existing diabetes conditions, the test monitors the effectiveness of their diabetes treatment.

Insulin test

• Evaluate insulin production.
• Diagnose an insulinoma (insulin-producing pancreatic islet cell tumor).
• Determine the cause of hypoglycemia.

Urinalysis

• Diabetic ketoacidosis (ketones)
• Kidney disease (blood cells and protein)
• Urinary tract infections (bacteria)