Type 1 Diabetes: Diagnosis
A type 1 diabetes diagnosis is often made in a hospital or emergency room after extremely the high blood glucose of undetected diabetes causes severe illness. In other cases, chronic infection or other initial symptoms raise the suspicion of diabetes, and testing occurs in a doctor’s office or outpatient lab.
The preferred blood test for diagnosing type 1 diabetes is the plasma glucose test. The test requires an eight-hour fast (no food or drink except water), after which a blood draw is performed. It is usually done in the morning. An oral glucose tolerance test (OGTT; blood draws taken at intervals up to four hours after a patient consumes a drink of 75 grams of glucose) can also be performed.
The following lab values are the American Diabetes Association practice guidelines for the diagnosis of diabetes:
A definitive diabetes diagnosis requires a second positive test performed on a different day. If symptoms of high blood glucose are extreme (e.g., diabetic ketoacidosis) and blood glucose levels are significantly elevated, your doctor may not require a second follow-up test.
In some cases, especially in those where it’s unclear whether type 1 or type 2 diabetes is present, a physician may also prescribe additional blood tests. These may include a c-peptide test (which measures levels of this protein associated with insulin production) or tests for islet cell antibodies (ICA), insulin auto-antibodies (IAA), and/or glutamic acid decarboxylase (a beta cell protein known as GAD).SOURCES:
1 - National Diabetes Information Clearinghouse. Diabetes Overview. (Accessed 2/19/08).
Reviewed by Francine Kaufman, MD. 4/08