Blood Glucose Test: MedlinePlus Medical Test (2024)

What is a Blood Glucose Test?

A blood glucose test measures the glucose levels in your blood. Glucose is a type of sugar. It is your body's main source of energy. A hormone called insulin helps move glucose from your bloodstream into your cells.

Too much or too little glucose in the blood can be a sign of a serious medical condition. High blood glucose levels (hyperglycemia) may be a sign of diabetes, a disorder that can cause serious, long-term health conditions.

High blood sugar may also be caused by other conditions that can affect insulin or glucose levels in your blood, such as problems with your pancreas or adrenal glands.

Low blood glucose levels (hypoglycemia) are common among people with type 1 diabetes and people with type 2 diabetes who take certain diabetes medicines. Certain conditions, such as liver disease, may cause low levels of blood glucose in people without diabetes, but this is uncommon. Without treatment, severe low blood sugar can lead to major health problems, including seizures and brain damage.

Other names: blood sugar, self-monitoring of blood glucose (SMBG), fasting plasma glucose (FPG), fasting blood sugar (FBS), fasting blood glucose (FBG), random blood sugar, glucose challenge test, oral glucose tolerance test (OGTT)

What is it used for?

A blood glucose test is used to find out if your blood sugar levels are in a healthy range. It is often used to help diagnose and monitor diabetes.

Why do I need a blood glucose test?

Your health care provider may order a blood glucose test if you have symptoms of high glucose levels or low glucose levels.

Symptoms of high blood glucose levels include:

  • Increased thirst and urination (peeing)
  • Blurred vision
  • Fatigue
  • Sores that don't heal
  • Weight loss when you're not trying to lose weight
  • Numbness or tingling in your feet or hands

Symptoms of low blood glucose levels include:

  • Feeling shaky or jittery
  • Hunger
  • Fatigue
  • Feeling dizzy, confused, or irritable
  • Headache
  • A fast heartbeat or arrhythmia (a problem with the rate or rhythm of your heartbeat)
  • Having trouble seeing or speaking clearly
  • Fainting or seizures

You may also need a blood glucose test if you have a high risk for developing type 2 diabetes. You're more likely to develop diabetes if you:

  • Are overweight or have obesity
  • Are age 45 or older
  • Have a family history of diabetes
  • Have high blood pressure
  • Don't exercise enough
  • Have a history of heart disease or stroke
  • Have had gestational diabetes (diabetes that happens only during pregnancy)

If you are pregnant, you will likely get a blood glucose test between the 24th and 28th week of your pregnancy to check for gestational diabetes.

What happens during a blood glucose test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out.

For some types of glucose blood tests, you will drink a sugary liquid and wait for an hour before your blood sample is taken:

  • A glucose challenge test is used to test for gestational diabetes in pregnancy. If your blood glucose level is higher than normal, you may have gestational diabetes. You'll need an oral glucose tolerance test (OGTT) to get a diagnosis.
  • An oral glucose tolerance test (OGTT) is used to diagnose gestational diabetes, and type 2 diabetes and prediabetes in people who aren't pregnant. A blood sample will be taken before you have a sugary drink and then again, every hour for the next 2 or 3 hours.

Will I need to do anything to prepare for the test?

If your provider orders a fasting blood glucose test or an oral glucose tolerance test, you will need to fast (not eat or drink) for at least eight hours before the test. Other blood glucose tests don't require any special preparations. Ask your provider whether you need to fast before your glucose test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly. After an oral glucose tolerance test, you may feel light-headed. Your provider may suggest that you plan to have someone take you home.

What do the results mean?

If your results show higher than normal glucose levels, it may mean you have or are at risk for getting diabetes. High glucose levels may also be a sign of:

  • Hyperthyroidism
  • Pancreas disorders
  • Stress from surgery, very serious illness, or trauma

If you have diabetes, lower than normal glucose levels may be caused by:

  • Side effects from certain diabetes medicines
  • Not eating enough, especially after taking diabetes medicine
  • Being more physically active than usual

If you don't have diabetes, low blood glucose levels may be a sign of:

  • Liver disease
  • Kidney disease
  • Underactive adrenal, pituitary, or thyroid gland (hypothyroidism)
  • Alcohol use disorder (AUD)

If your glucose results are not normal, it doesn't always mean you have a medical condition that needs treatment. Certain medicines and stress can affect glucose levels. To learn what your test results mean, talk with your health care provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I should know about a blood glucose test?

If you have diabetes, you may need to do blood sugar testing at home every day to help manage your blood glucose levels. There are two ways to do this:

  • Blood glucose meters require you to prick your finger with a small device called a lancet. You apply a drop of blood to a test strip and insert it into a small, electronic glucose meter, which measures the glucose is in your blood.
  • Continuous glucose monitors (CGM) use a tiny sensor that you insert under your skin. Every few minutes, the sensor measures glucose levels in fluids between your cells. If your glucose is too high or too low, you use a blood glucose meter to check your blood levels before making changes to raise or lower your glucose level.

References

  1. American Diabetes Association [Internet]. Arlington (VA): American Diabetes Association; c1995–2022. The Big Picture: Checking Your Blood Sugar [cited 2022 Apr 12]; [about 8 screens]. Available from: https://diabetes.org/living-with-diabetes/treatment-care/checking-your-blood-sugar
  2. American Diabetes Association [Internet]. Arlington (VA): American Diabetes Association; c1995–2022. Gestational Diabetes; [cited 2022 Apr 12]; [about 6 screens]. Available from: https://www.diabetes.org/diabetes/gestational-diabetes
  3. American Pregnancy Association [Internet]. Irving (TX): American Pregnancy Association; c2021. Glucose Tolerance Test; [cited 2022 Apr 12]; [about 7 screens]. Available from: http://americanpregnancy.org/prenatal-testing/glucose-tolerence-test/
  4. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Diabetes Basics; [updated 2021 Dec 16; cited 2022 Apr 12]; [about 3 screens]. Available from: https://www.cdc.gov/diabetes/about/
  5. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Monitoring Your Blood Sugar; [updated 2021 Aug 10; cited 2022 Apr 12]; [about 3 screens]. Available from: https://www.cdc.gov/diabetes/diabetes-testing/monitoring-blood-sugar.html
  6. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Considerations for Blood Glucose Monitoring and Insulin Administration; [updated 2011 Mar 2; cited 2022 Apr 12]; [about 4 screens]. Available from: https://www.cdc.gov/injection-safety/hcp/infection-control/
  7. FDA: US Food and Drug Administration [Internet]. Silver Spring (MD): US Department of Health and Human Services; FDA expands indication for continuous glucose monitoring system, first to replace fingerstick testing for diabetes treatment decisions; 2016 Dec 20 [cited 2022 Apr 12]; [about 2 screens]. Available from: https://www.fda.gov/news-events/press-announcements/fda-expands-indication-continuous-glucose-monitoring-system-first-replace-fingerstick-testing
  8. Godinjak A, Iglica A, Burekovic A, Jusufovic S, Ajanovic A, Tancica I, Kukuljac A. Hyperglycemia in Critically Ill Patients: Management and Prognosis. Med Arch. [Internet]. 2015 Jun [cited 2022 Apr 12]; 69(3):157-60. Available from: https://pubmed.ncbi.nlm.nih.gov/26261382/
  9. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Glucose Monitoring; 317 p.
  10. Mathew P, Thoppil D. Hypoglycemia. [Updated 2022 Jan 4; cited 2022 Apr 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534841/
  11. Mathew TK, Tadi P. Blood Glucose Monitoring. [Updated 2021 Aug 11; cited 2022 Apr 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555976/
  12. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Diabetes Mellitus (DM); [reviewed 2020 Sep; cited 2022 Apr 12]; [about 12 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/diabetes-mellitus-dm
  13. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Hypoglycemia (Low Blood Sugar); [reviewed 2020 Sep; cited 2022 Apr 12]; [about 5 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/hypoglycemia
  14. Mouri MI, Badireddy M. Hyperglycemia. [Updated 2021 May 10; cited 2022 Apr 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430900/
  15. National Cancer Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; NCI Dictionary of Cancer Terms: glucose; [cited2022 Apr 12]; [about 1 screen]. Available from: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/glucose
  16. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [updated 2022 Mar 24; cited 2022 Apr 12]; [about 7 screens]. Available from: https://www.nhlbi.nih.gov/health/blood-tests
  17. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Continuous Glucose Monitoring; [reviewed 2017 Jun; cited 2022 Apr 12]; [about 5 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/managing-diabetes/continuous-glucose-monitoring
  18. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Diabetes Tests & Diagnosis;[reviewed 2016 Dec; cited 2022 Apr 12]; [about 4 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis
  19. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Low Blood Glucose (Hypoglycemia); [reviewed 2021 Jul; cited 2022 Apr 12]; [about 9 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/low-blood-glucose-hypoglycemia
  20. Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Glucose Testing; [cited 2022 Apr 12]; [about 10 screens]. Available from: https://www.testing.com/glucose-testing/
  21. UCSF Medical Center [Internet]. San Francisco (CA): The Regents of the University of California; c2002-2022. Medical Tests: Blood Sugar Test; [reviewed 2018 Feb 22; cited 2022 Apr 12]; [about 4 screens]. Available from: https://www.ucsfhealth.org/medical-tests/blood-sugar-test
  22. UCSF Medical Center [Internet]. San Francisco (CA): The Regents of the University of California; c2002–2022. Medical Tests: Glucose Urine Test; [reviewed 2018 Feb 18; cited 2022 Apr 12]; [about 2 screens]. Available from: https://www.ucsfhealth.org/medical-tests/glucose-urine-test
  23. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Glucose (Blood); [cited 2022 Apr 12]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=glucose_blood
Blood Glucose Test: MedlinePlus Medical Test (2024)

References

Top Articles
Latest Posts
Recommended Articles
Article information

Author: Terrell Hackett

Last Updated:

Views: 6209

Rating: 4.1 / 5 (52 voted)

Reviews: 91% of readers found this page helpful

Author information

Name: Terrell Hackett

Birthday: 1992-03-17

Address: Suite 453 459 Gibson Squares, East Adriane, AK 71925-5692

Phone: +21811810803470

Job: Chief Representative

Hobby: Board games, Rock climbing, Ghost hunting, Origami, Kabaddi, Mushroom hunting, Gaming

Introduction: My name is Terrell Hackett, I am a gleaming, brainy, courageous, helpful, healthy, cooperative, graceful person who loves writing and wants to share my knowledge and understanding with you.