Symptoms and Diagnosis of Type 1 Diabetes
Symptoms
The symptoms of type 1 diabetes usually come on suddenly. They may include:
- increased thirst
- increased hunger
- feeling very tired
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- increased urination
- sudden weight loss
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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 sugar (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 used to diagnose diabetes are the casual plasma glucose test (a blood test taken at any time of day without regard to time since last meal), the oral glucose tolerance test (OGTT: a blood test taken 2 hours after drinking glucose dissolved in water), and the glycated hemoglobin (A1C). A person recently diagnosed with type 1 diabetes may not have an elevated A1C. This test is not often used when type 1 diabetes is suspected.
A diagnosis of diabetes is made if a person has any of the following test results1:
- FPG is 126 mg/dL or higher.
- High blood sugar (hyperglycemia) symptoms exist and casual plasma glucose is 200 mg/dL or higher.
- Plasma glucose is 200 mg/dL or higher at 2 hours during an OGTT.
- A1C is greater than or equal to 6.5%.
If any of these test results occur, testing should be repeated on a different day to confirm the diagnosis.
Reference
1. American Diabetes Association. Standards of medical care in diabetes—2011. Diabetes Care. 2011;34(suppl 1):S11-S61.
