Diagnosis and Testing

Reviewed by: HU Medical Review Board | Last reviewed: October 2020.

Glucose tests are used to measure the amount of glucose (sugar) in your blood. Your doctor may use 1 of the tests to see if you have diabetes. If you have already been diagnosed with diabetes, you can use these tests to see how well you are controlling your blood sugar levels.

Since many people who have type 2 diabetes have no or mild symptoms, glucose testing can give you and your doctor important clues about your health. Testing recommendations include:1

  • People over age 45 should have an initial test; if results are normal, testing should be done every 3 years
  • Anyone who is overweight or has other risk factors for diabetes, including high blood pressure and a family history of diabetes, should be tested each year
  • Any woman who is pregnant should be tested between 24 and 28 weeks of pregnancy; women who previously had gestational diabetes should be tested every 3 years
  • Anyone who has been diagnosed with prediabetes should be tested each year

Anyone who is experiencing any of the common signs of high blood sugar, such as blurred vision or excessive thirst, should talk to their doctor and be tested as soon as possible.2

Early detection and diagnosis of type 2 diabetes are very important. In type 2 diabetes, the body does not use insulin well. This is a hormone that helps glucose (sugar) get into cells so it can be used for energy. Since there is not enough insulin to help this process, too much glucose stays in the blood.2

Type 2 diabetes increases your risk for many serious health problems, especially if it is left untreated. Over time, high blood glucose levels can affect many of your organs, including your heart, nerves, eyes, and kidneys. Glucose testing is 1 of the best tools to better understand and manage your health.2

Tests used to diagnose type 2 diabetes

There are a few different tests that can be used to diagnose diabetes, and doctors will typically use 1 or more tests when determining if you have diabetes. These tests measure your blood sugar level. Testing is simple and usually done in a doctor’s office or a lab. If your test results show that your blood sugar level is high, your doctor may have you take another test on a different day to recheck your level and confirm your diagnosis.3

Fasting blood glucose test

This is the quickest and simplest test used to diagnose diabetes. It measures the level of glucose (sugar) in your blood. You will need to fast (not eat or drink anything except water) for at least 8 hours before your test.

If your fasting blood glucose level is higher than 126 mg/DL, you will likely be diagnosed with diabetes.2

Hemoglobin A1C test

This test is commonly used to diagnose diabetes, as well as monitor blood sugar levels in people who have already been diagnosed. The hemoglobin A1C test measures your average blood glucose (sugar) level over the past 3 months. An A1C level of 6.5 percent or higher means that you have diabetes. Also, the higher your A1C level, the more likely you are to experience complications of diabetes.4

Oral glucose tolerance test

This test checks your blood sugar level before and after you drink a sweet drink that contains glucose (sugar). It measures how your body responds to sugar. The oral glucose tolerance test is most often used to diagnose gestational diabetes, which is a type of diabetes that can affect pregnant women. It is also sometimes used to diagnose type 2 diabetes. Different numbers are used to diagnose type 2 diabetes or gestational diabetes.5

Random blood glucose test

The random blood glucose test measures how much glucose (sugar) you have in your blood at the time you are tested. Doctors often use this test when a person is experiencing 1 or more of the common symptoms of diabetes, like blurred vision or excessive thirst. If your blood glucose level is 200 mg/dL, your doctor will probably diagnose you with diabetes.6

Understanding your blood glucose test results

Understanding what your test results mean can help you better manage your health. It is also important to talk to your doctor about what your specific results mean and ask any questions you might have about your treatment plan.

Prediabetes test results

If your test results show signs of prediabetes, you are at greater risk of developing type 2 diabetes. However, you can lower your risk and even return your blood glucose levels to the normal range if you make lifestyle changes like eating a healthier diet and being more physically active. Talk to your doctor about what steps you can take.

Diabetes test results

If you receive a new diagnosis of type 2 diabetes after being tested, it is important to talk with your doctor about what your diagnosis means and the best treatment plan for you. There are many steps you can take to keep your blood sugar levels under control and places where you can get the support you need.

If you have already been diagnosed with type 2 diabetes and your test results show that your blood sugar is not well controlled, talk with your doctor about changes you can make.

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