High blood levels of glucose can cause several problems, including:

• Blurry vision
• Excessive thirst
• Fatigue
• Frequent urination
• Hunger
• Weight loss

However, because type 2 diabetes develops slowly, some people with high blood sugar experience no symptoms at all.

Symptoms of type 1 diabetes:

• Fatigue
• Increased thirst
• Increased urination
• Nausea
• Vomiting
• Weight loss in spite of increased appetite

Patients with type 1 diabetes usually develop symptoms over a short period of time. The condition is often diagnosed in an emergency setting.

Symptoms of type 2 diabetes:

• Blurred vision
• Fatigue
• Increased appetite
• Increased thirst
• Increased urination

A urine analysis may be used to look for glucose and ketones from the breakdown of fat. However, a urine test alone does not diagnose diabetes.

The following blood tests are used to diagnose diabetes:

• Fasting blood glucose level -- diabetes is diagnosed if higher than 126 mg/dL on two occasions. Levels between 100 and 126 mg/dL are referred to as impaired fasting glucose or prediabetes. These levels are considered to be risk factors for type 2 diabetes and its complications.
• Oral glucose tolerance test -- diabetes is diagnosed if glucose level is higher than 200 mg/dL after 2 hours. (This test is used more for type 2 diabetes.)
• Random (non-fasting) blood glucose level -- diabetes is suspected if higher than 200 mg/dL and accompanied by the classic diabetes symptoms of increased thirst, urination, and fatigue. (This test must be confirmed with a fasting blood glucose test.)

Persons with diabetes need to have their hemoglobin A1c (HbA1c) level checked every 3 - 6 months. The HbA1c is a measure of average blood glucose during the previous 2 - 3 months. It is a very helpful way to determine how well treatment is working.