Symptoms and Diagnosis of Type 1 Diabetes

The symptoms of type 1 diabetes usually come on suddenly. They include:

Diagnosis

Type 1 diabetes is usually diagnosed in children and young adults, and was previously known as juvenile diabetes. However, it can develop at any age throughout adulthood. Generally, people with type 1 diabetes are diagnosed when symptoms appear suddenly or they experience extremely high blood glucose levels.

The preferred test for diagnosing type 1 diabetes is the fasting plasma glucose (FPG) test. This blood test requires fasting (no food or drink except water) for at least 8 hours and is usually done in the morning. Other tests are the casual plasma glucose test (a blood test taken at any time of day without regard to time since last meal), and the oral glucose tolerance test (OGTT; a blood test taken 2 hours after drinking glucose dissolved in water).

A diagnosis of diabetes is made if a person has any of the following test results¹:

• FPG is 126 mg/dl or higher; or
• Diabetes symptoms exist and casual plasma glucose is 200 mg/dl or higher; or
• Plasma glucose is 200 mg/dl or higher at 2 hours during an OGTT

If any of these test results occurs, testing should be repeated on a different day to confirm the diagnosis.

Reference
1. American Diabetes Association. Standards of medical care in diabetes. Diabetes Care. 2008;31 (suppl 1): S12–S54.