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Understanding a Type 2 Diabetes Diagnosis

Diagnosing Type 2 Diabetes

Type 2 diabetes is a manageable condition. Once you’re diagnosed, you can learn what to do to stay healthy.

Diabetes is grouped into different types. The most commonly diagnosed are gestational diabetes, type 1 diabetes, and type 2 diabetes.

Gestational Diabetes

Maybe you have a friend who was told she had diabetes during pregnancy. That type is called gestational diabetes. It can develop during the second or third trimester of pregnancy. Gestational diabetes usually goes away after the baby is born.

Type 1 Diabetes

You may have had a childhood friend with diabetes who had to take insulin every day. That type is called type 1 diabetes. The peak age of onset is in the midteens. According to the Centers for Disease Control and Prevention (CDC), type 1 makes up 5 percent of all cases of diabetes.

Type 2 Diabetes

Type 2 diabetes makes up 90 to 95 percent of all diagnosed cases of diabetes, according to the CDC. It is also called adult-onset diabetes. Although it can occur at any age, it’s more common in people older than 40.

If you think you might have diabetes, talk to your doctor. Uncontrolled type 2 diabetes can cause severe complications, such as:

  • amputation of the legs and feet
  • blindness
  • heart disease
  • kidney disease
  • stroke

According to the CDC, diabetes is the 7th leading cause of death in the United States. People with diabetes are 1.5 times as likely to die as people of the same age who don’t have diabetes. Many of the severe side effects of diabetes can be avoided with treatment. That’s why it’s so important to be diagnosed as soon as possible.

Symptoms of Type 2 Diabetes

Some people are diagnosed with type 2 diabetes because they have symptoms. Early diabetes symptoms include:

  • increased or frequent urination
  • increased thirst
  • fatigue
  • cuts or sores that won’t heal
  • blurry vision

Most often, people are diagnosed through routine screening tests. In general, routine screening for diabetes starts at age 45. You may need to be screened sooner if you:

  • are overweight
  • live a sedentary lifestyle
  • have a family history of type 2 diabetes
  • have a history of gestational diabetes or have given birth to a baby over 9 pounds
  • are of certain ethnicity (African-American, Native American, Latino, Asian, and Pacific Islander)
  • have a low good cholesterol level (HDL) or a high triglyceride level

How Doctors Diagnose Type 2 Diabetes

The symptoms of type 2 diabetes often develop gradually. Because you may or may not have symptoms, your doctor will use blood tests to confirm your diagnosis. The tests measure the amount of sugar, or glucose, in your blood. The tests used are the:

  • glycated hemoglobin (A1C) test
  • fasting plasma glucose test
  • random plasma glucose test
  • oral glucose tolerance test

Your doctor will perform one or more of the above tests more than once to confirm your diagnosis.

Glycated Hemoglobin (A1C) Test

The glycated hemoglobin (A1C) test is a long-term measure of blood sugar control. It allows your doctor to figure out what your average blood sugar level has been for the past few months.

This test measures the percentage of blood sugar attached to hemoglobin. Hemoglobin is the oxygen-carrying protein in your red blood cells. The higher your A1C is, the higher your recent blood sugar levels have been.

The A1C test is not as sensitive as the fasting plasma glucose and the random plasma glucose tests. This means that it identifies fewer cases of diabetes. Your doctor will send your sample to a certified laboratory for diagnosis. This may mean that it takes longer to get your results than with a test conducted in the doctor’s office.

An advantage of the A1C test is convenience. You don’t have to fast before this test. The blood sample can be collected at any time of day. Also, the test results are not affected by stress or illness.

Your doctor will go over your results with you. For a glycated hemoglobin (A1C) test, here is what your results could mean:

  • diabetes = A1C of 6.5 percent or higher
  • prediabetes = A1C between 5.7 and 6.4 percent
  • normal = A1C less than 5.7 percent

A1C testing can also be used to monitor your blood sugar control after you’ve been diagnosed. Your A1C levels should be checked several times a year.

Fasting Plasma Glucose Test

In some circumstances, the A1C test is not valid. For example, it can’t be used by pregnant women or by people who have a hemoglobin variant. For these people, fasting blood sugar testing may be used instead. In this case, a sample of your blood will be taken after you have fasted overnight.

Unlike the A1C test, this test measures the amount of sugar in your blood at a single point in time. Your results can be affected if you are stressed or sick. Blood sugar values are expressed in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

Your doctor will go over your results with you. For a fasting plasma glucose test, here is what your results could mean:

  • diabetes = fasting blood sugar of 126 mg/dL or higher
  • prediabetes = fasting blood sugar of 100 to 125 mg/dL
  • normal = fasting blood sugar less than 100 mg/dL

Random Plasma Glucose Test

Random blood sugar testing is used in people with symptoms of diabetes. A random blood sugar test can be done at any time of day. The test looks at blood sugar without considering your last meal.

No matter when you last ate, a random blood sugar test of 200 mg/dL or above suggests that you have diabetes. This is particularly true if you already have symptoms of diabetes.

Your doctor will go over your results with you. For a random plasma glucose test, here is what your results could mean:

  • diabetes = random blood sugar of 200 mg/dL or more
  • prediabetes = random blood sugar level between 140 and 199 mg/dL
  • normal = random blood sugar less than 140 mg/dL

Oral Glucose Tolerance Test

The oral glucose tolerance test also requires that you fast overnight. When you arrive at your appointment, you will take a fasting blood sugar test. Then you will drink a sugary liquid. After you’re done, your blood sugar levels will be tested periodically for several hours.

To prepare for this test, the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recommends that you eat at least 150 grams of carbohydrates per day for the three days before the test. Foods like bread, cereal, pasta, potatoes, fruit (fresh and canned), and clear broth all contain carbohydrates. Tell your doctor about any stress or illness you are experiencing. Make sure your doctor knows about all of the medications you are taking. Stress, illness, and medications can all affect the results of the oral glucose tolerance test.

Your doctor will go over your results with you. For an oral glucose tolerance test, here is what your results could mean:

  • diabetes = blood sugar of 200 mg/dL or more after two hours
  • prediabetes = blood sugar between 140 and 199 mg/dL after two hours
  • normal = blood sugar less than 140 mg/dL after two hours 

Glucose tolerance tests are also used to diagnose gestational diabetes during pregnancy.

Getting a Second Opinion

You should always feel free to get a second opinion if you have any concerns or doubts about your diagnosis. You have every right to a second opinion.

You should also consider asking for new tests if you change doctors. Different doctors’ offices use different laboratories to process samples. The NIDDK says it can be misleading to compare results from different labs. Remember that your doctor will need to repeat any test to confirm your diagnosis.

Are Test Results Ever Wrong?

In some people, a blood sugar test may show that you have diabetes but an A1C test does not. The reverse can also be true. How does this happen? You could be in an early stage of diabetes. Your blood sugar levels may not be high enough to show on every test. The A1C test can be wrong in some people of African, Mediterranean, or Southeast Asian heritage. Also, the A1C test can be too low in people with anemia or heavy bleeding. It can be too high in people with iron deficiency anemia. Your doctor will repeat the tests before making a diagnosis.

Treatment Planning

A diagnosis of diabetes is only the first step. Once you know you have diabetes, you can work with your doctor to create a treatment plan that’s right for you. It’s important to follow through on all your monitoring and medical appointments. Getting your blood tested and tracking your symptoms are important steps to ensure long-term health.

Prepare a treatment action plan. Talk with your doctor about your blood sugar goal. The National Diabetes Education Program says that the goal for many people is an A1C below 7. Ask your doctor how often to test your blood sugar. Create a self-care plan to manage your diabetes. Include actions like eating healthy food, exercising, stopping smoking, and checking your blood sugar. At every visit, talk with your doctor about how your self-care plan is working for you.


There is no existing cure for type 2 diabetes. However, this condition is highly manageable, with various effective treatment options. The first step is diagnosis and understanding your results. To confirm your diagnosis, you doctor will need to repeat one or more of these tests: AIC, fasting blood glucose, random blood glucose, or oral glucose tolerance. If you are diagnosed with diabetes, create a self-care plan and set a blood sugar goal. 

Content licensed from:

Written by: The Healthline Editorial Team
Medically reviewed on: Feb 05, 2016: George Krucik, MD, MBA

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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