Type 2 diabetes is easy to diagnose once someone gets tested for it. As many as one-third of people with type 2 diabetes do not know they have the disease. Early on, diabetes symptoms are mild and may be easily confused with other conditions or signs of aging.

Type 2 diabetes is most commonly diagnosed in people age 45 or older, but younger adults and even children can develop type 2 diabetes too. Routine testing is recommended for people who:

• Are age 45 or older
• Are between the ages of 19 and 44, and overweight or obese
• Are between the ages of 10 and 18, overweight or obese, with additional risk factors such as family history of diabetes or low birth weight
• Had gestational diabetes while pregnant
• Are currently pregnant

Most people are diagnosed with diabetes by their primary care physician or family doctor. Your general practitioner may continue to treat your diabetes, or they may refer you to an endocrinologist. Endocrinologists specialize in diseases of the glands and hormone imbalance — diabetes involves problems with the pancreas, a gland that produces the hormone insulin. Read more about causes of diabetes.

How Is Type 2 Diabetes Diagnosed?

The doctor will draw a small blood sample to test your blood glucose level. In people with type 2 diabetes, cells become resistant to insulin. Insulin is the hormone necessary to allow cells to take in glucose from the bloodstream and regulate how much glucose remains in your blood. As diabetes progresses, cells can take in less and less glucose, and blood glucose levels rise.

There are several ways of testing blood glucose. The doctor will likely repeat the blood test on another day soon after to make sure the diagnosis is correct.

A1C

The results of the A1C test, also referred to as HbA1c, glycated hemoglobin, or glycohemoglobin test, show your average blood glucose over the past two to three months. A1C is used to diagnose type 2 diabetes and to monitor how well blood glucose is being managed in people taking treatments for type 2 diabetes.

A1C is expressed as a percentage.

• Less than 5.7 percent is considered normal.
• 5.7 percent to 6.4 percent indicates prediabetes.
• 6.5 percent or higher indicates diabetes.

Oral Glucose Tolerance Test (OGTT)

For the OGTT, the doctor will take a blood sample, then provide a sweet beverage with a high glucose content. After waiting two hours, another blood sample will be taken to check how your blood glucose level has risen in response to the drink.

OGTT results are expressed in milligrams of glucose per deciliter of blood (often written as mg/dL).

• Less than 100 milligrams per deciliter after an eight-hour fast is considered normal.
• 100 to 125 milligrams per deciliter indicates prediabetes.
• 126 milligrams per deciliter or higher indicates diabetes.

Fasting Plasma Glucose (FPG)

A fasting plasma glucose test is usually scheduled early in the morning. For an accurate result, you should fast — not eat or drink anything but water — for at least eight hours before the blood sample is taken.

Results are expressed in milligrams of glucose per deciliter, and diagnostic ranges are the same as for the oral tolerance test.

Random Plasma Glucose Test

A blood sample for a random or casual blood glucose test can be taken at any time. Results are expressed in miligrams per deciliter. A test result of 200 milligrams per deciliter or higher indicates diabetes. Any test would need to be repeated to confirm the diagnosis of type 2 diabetes.

Condition Guide

• Type 2 Diabetes — An Overview
• Diabetes — The Path to Diagnosis
• Symptoms of Type 2 Diabetes
• Treatments for Type 2 Diabetes
• Types of Diabetes
• What Causes Type 2 Diabetes?

References

1. Diabetes — Mayo Clinic
2. Diagnosing Diabetes and Learning About Prediabetes — American Diabetes Association
3. Diabetes Tests & Diagnosis — National Institute of Diabetes and Digestive and Kidney Diseases Health Information Center