Medically Reviewed by Expert Board

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.

.
This article was last modified on

What Is Prediabetes?

Prediabetes is a medical condition in which your blood sugar level is too high but not high enough to be diagnosed with diabetes.

Blood sugar is also known as blood glucose. Glucose is the sugar that the body uses as its main source of energy. Your body obtains glucose from the food you eat. The pancreas makes a hormone called insulin that helps the body’s cells use glucose and remove it from the bloodstream.

Blood glucose levels can become too high if the pancreas can’t make enough insulin or if your body’s cells resist the effect of insulin and don’t properly take glucose in. Having too much glucose in the blood can lead to type 2 diabetes, which can cause damage to many organs and tissues if it isn’t controlled.

Having prediabetes increases the risk of developing diabetes and other serious health problems such as heart disease or stroke. Identifying prediabetes through testing can help you take the steps needed to prevent these and other complications of high blood sugar.

The Role of Prediabetes Tests

Prediabetes tests are used to screen people who are at risk for prediabetes or diabetes.

Screening means testing to find health concerns before they have caused any signs or symptoms. Prediabetes affects about one-third of all American adults, but it does not usually cause any noticeable symptoms. This means that a person can have prediabetes but not realize it.

People who are diagnosed with prediabetes have a much greater risk of developing full diabetes within the next ten years. They are also more likely to have a stroke or heart disease.

Identifying prediabetes with screening tests can help doctors recommend diet and lifestyle changes that can delay the onset of diabetes or even prevent it altogether.

Who should get testing?

Your doctor may recommend that you take a screening test if you are at risk for prediabetes or diabetes. If any of the following factors apply to you, you may want to talk to your doctor about getting tested:

  • Being 45 years old or older
  • Being overweight
  • Having one or more close relatives with diabetes
  • Not getting regular physical exercise
  • Having a history of gestational diabetes, which is a type of diabetes that develops in pregnancy
  • Having polycystic ovary syndrome, which is a condition involving abnormal sex hormone levels
  • Having a history of cardiovascular problems including high blood pressure, high cholesterol, stroke, and/or heart disease

Research has found that people in certain racial or ethnic groups are at a higher risk of developing diabetes. While the reasons behind this increased risk are complex and require further study, doctors may recommend prediabetes screening if you are from these backgrounds:

  • African American or Black
  • Alaska Native
  • American Indian or Native American
  • Asian
  • Hispanic or Latino/Latina
  • Native Hawaiian
  • Pacific Islander

Getting test results

You may get the results of your prediabetes test soon after the test is completed, or you may need to wait for a few business days for your results to be available. The results may be mailed to you or made accessible through an online portal.

Your doctor may want to discuss the results and any health recommendations resulting from them with you at a follow-up appointment either in person or over the phone.

Types of Prediabetes Tests

Prediabetes is diagnosed with tests that measure the amount of glucose in the blood. These tests involve blood draws that take samples of blood from a vein in your arm.

A prediabetes screening test may be performed alone or with other tests. The type and timing of the test you receive will depend on your specific situation.

The following blood tests are used to screen for high blood sugar in order to diagnose prediabetes and diabetes:

  • Fasting plasma glucose test: This test measures your blood glucose level after you have fasted overnight. For this test, you need to go without eating and without drinking anything but water for eight hours or longer.
  • Hemoglobin A1c test: This test shows how much glucose in your blood is attached to hemoglobin, a protein in red blood cells. This test provides a measurement of your average blood glucose level over the previous 2 to 3 months. You do not need to fast before taking this test.
  • Glucose tolerance test: This test evaluates how well you metabolize glucose after fasting overnight and then drinking a sweetened drink. The glucose tolerance test typically involves multiple blood samples taken over several hours to see how your blood sugar changes.

Regardless of which test is initially performed, your doctor may want you to repeat the test if it shows that your glucose levels are abnormal. Your doctor may also want you to take a different test to confirm the first test’s results.

If your prediabetes test is normal, your doctor may recommend that you repeat it at least once every three years depending on your risk factors. If your test shows that you have diabetes, your doctor may ask you to return every year for repeated testing.

Getting Tested for Prediabetes

Your doctor is generally the one to order prediabetes blood testing. Depending on what test is ordered, it may be conducted in various settings, such as your doctor’s office, a clinic, lab, or hospital.

At-home testing

The fasting plasma glucose test and glucose tolerance test are not done at home. Both of these tests must be performed in a clinical setting and require interpretation by trained health professionals.

Many at-home hemoglobin A1c tests are commercially available. These tests are mainly used by people with diabetes to monitor their glucose levels, but some are also marketed as screening tests for prediabetes and diabetes. These tests involve taking a blood sample from your fingertip. That sample may be analyzed at home on a small device or sent to a laboratory where glucose levels are measured.

You may want to talk to your doctor about at-home screening using these tests. Your doctor can discuss whether these tests would be right for you, as well as whether you would need additional tests to confirm their results.

View Sources

A.D.A.M. Medical Encyclopedia. Prediabetes. Updated January 1, 2020. Accessed December 3, 2021. https://medlineplus.gov/ency/patientinstructions/000778.htm

American Diabetes Association. Understanding A1C: Diagnosis. Date unknown. Accessed December 3, 2021. https://www.diabetes.org/a1c/diagnosis

American Heart Association. Symptoms, diagnosis and monitoring of diabetes. Updated May 5, 2021. Accessed December 3, 2021. https://www.heart.org/en/health-topics/diabetes/symptoms-diagnosis–monitoring-of-diabetes

Brutsaert E. Diabetes mellitus (DM). Merck Manuals Consumer Edition. Updated September 2020. Accessed December 3, 2021. https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/diabetes-mellitus-dm

Centers for Disease Control and Prevention. Prediabetes – your chance to prevent type 2 diabetes. Updated June 11, 2020. Accessed December 3, 2021. https://www.cdc.gov/diabetes/basics/prediabetes.html

Centers for Disease Control and Prevention. What is diabetes? Updated June 11, 2020. Accessed December 3, 2021. https://www.cdc.gov/diabetes/basics/diabetes.html

Hill-Briggs F, Adler NE, Berkowitz SA, et al. Social determinants of health and diabetes: A scientific review [published online ahead of print, 2020 Nov 2]. Diabetes Care. 2020;44(1):258-279. doi:10.2337/dci20-0053

Inzucchi SE, Lupsa B. Clinical presentation, diagnosis, and initial evaluation of diabetes mellitus in adults. In: Nathan DM, Wolfsdorf JI, eds. UpToDate. Updated October 29, 2021. Accessed December 3, 2021. https://www.uptodate.com/contents/clinical-presentation-diagnosis-and-initial-evaluation-of-diabetes-mellitus-in-adults

MedlinePlus: National Library of Medicine. Prediabetes. Updated February 23, 2021. Accessed December 3, 2021. https://medlineplus.gov/prediabetes.html

MedlinePlus: National Library of Medicine. Diabetes tests. Updated September 27, 2021. Accessed December 3, 2021. https://medlineplus.gov/lab-tests/diabetes-tests/

National Institute of Diabetes and Digestive and Kidney Diseases. Prediabetes screening: How and why. Date unknown. Accessed December 3, 2021. https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/diabetes/game-plan-preventing-type-2-diabetes/prediabetes-screening-how-why

National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes tests & diagnosis. Updated December 2016. Accessed December 3, 2021. https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis

National Institute of Diabetes and Digestive and Kidney Diseases. Preventing type 2 diabetes. Updated December 2016. Accessed December 3, 2021. https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-type-2-diabetes

National Institute of Diabetes and Digestive and Kidney Diseases. What is diabetes? Updated December 2016. Accessed December 3, 2021. https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes

National Institute of Diabetes and Digestive and Kidney Diseases. Insulin resistance & prediabetes. Updated May 2018. Accessed December 3, 2021. https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance

U.S. Preventive Services Task Force. Prediabetes and type 2 diabetes: Screening. Updated August 24, 2021. Accessed December 3, 2021. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/screening-for-prediabetes-and-type-2-diabetes

Ask a Laboratory Scientist

Ask a Laboratory Scientist

This form enables patients to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. Please allow 2-3 business days for an email response from one of the volunteers on the Consumer Information Response Team.

Send Us Your Question