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Results
By Mayo Clinic staffResults of the glucose tolerance test are given in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).
Type 2 diabetes
If you're being tested for type 2 diabetes, two hours after drinking the glucose solution:
- A normal blood glucose level is lower than 140 mg/dL (7.8 mmol/L).
- A blood glucose level between 140 mg/dL and 199 mg/dL (7.8 and 11 mmol/L) is considered impaired glucose tolerance, or prediabetes. If you have prediabetes, you're at risk of eventually developing type 2 diabetes. You're also at risk of developing heart disease, even if you don't develop diabetes.
- A blood glucose level of 200 mg/dL (11.1 mmol/L) or higher may indicate diabetes.
If the results of your glucose tolerance test indicate type 2 diabetes, your doctor may repeat the test on another day or use another blood test to confirm the diagnosis. Various factors can affect the accuracy of the glucose tolerance test, including illness, activity level and certain medications.
Gestational diabetes
If you're being tested for gestational diabetes, your doctor will consider the results of each blood glucose test. If two or more of the tests are higher than normal, you'll be diagnosed with gestational diabetes.
- A normal fasting blood glucose level is lower than 95 mg/dL (5.3 mmol/L).
- One hour after drinking the glucose solution, a normal blood glucose level is lower than 180 mg/dL (10 mmol/L).
- Two hours after drinking the glucose solution, a normal blood glucose level is lower than 155 mg/dL (8.6 mmol/L).
- Three hours after drinking the glucose solution, a normal blood glucose level is lower than 140 mg/dL (7.8 mmol/L).
If you're diagnosed with gestational diabetes, you can prevent complications by carefully managing your blood glucose level throughout the rest of your pregnancy.
- American Diabetes Association. Standards of medical care in diabetes — 2013. Diabetes Care. 2013;36(suppl):1.
- Evensen AE. Update on gestational diabetes mellitus. Primary Care. 2012;39:83.
- Glucose. Lab Tests Online. http://labtestsonline.org/understanding/analytes/glucose/tab/glance. Accessed Dec. 7, 2012.
- McCullough DK. Diagnosis of diabetes mellitus. http://www.uptodate.com/index. Accessed Dec. 7, 2012.
- The American College of Obstetricians and Gynecologists (committee opinion). Screening and diagnosis of gestational diabetes mellitus. Obstetrics and Gynecology. 2011;118:751.
- Castro MR (expert opinion). Mayo Clinic, Rochester, Minn. April 8, 2013.
- Coustan DR, Jovanovic L. Screening and diagnosis of diabetes mellitus during pregnancy. http://www.uptodate.com/home. Accessed April 2, 2013.
- AskMayoExpert. What tests are needed to confirm the diagnosis of gestational diabetes mellitus during pregnancy? Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2013.
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