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How Do Doctors Check for Type 2 Diabetes

If your healthcare provider is concerned about a potential diagnosis of type II diabetes, you will likely receive a series of laboratory tests that, together with other signs and symptoms of type II diabetes, can help definitively establish the diagnosis. Diagnosing Type 2 Diabetes One of the hallmarks of type II diabetes is hyperglycemia, which is a fancy technical term for high blood sugar. Aside from diabetes, hyperglycemia can present temporarily in non-diabetic adults with severe illness; therefore, the tests described below will help rule out other causes of hyperglycemia.

  1. Random blood sugar test: a measure of your blood sugar levels at random during any time of the day, regardless of when you last ate or drank. Normal values: 70-140mg/dL

  2. Fasting plasma glucose test: a measure of your blood sugar levels after not eating or drinking for 8-12 hours, usually overnight. Normal values are below 100mg/dL.

  3. Hemoglobin A1C test: Hemoglobin is a protein in your red blood cells that helps them carry oxygen. Hemoglobin A1C is a form of hemoglobin that is linked to sugar. The hemoglobin A1C test measures how much sugar is bound to your hemoglobin and tells you your average blood sugar levels over the past two to three months. It can be performed at any time of the day, regardless of when you last ate or drank. Normal values: 4-5.6%.

  4. Oral glucose tolerance test: This is a test that involves getting your blood sugar levels measured at baseline, and again one and two hours after drinking a special sugar solution. This measures your body’s response to sugar intake. The test also requires you to fast for 8 hours prior, and therefore is not commonly used to screen for diabetes except in pregnant individuals.

Getting Diagnosis of Diabetes Type II diabetes is diagnosed with any of the following results:

  1. A fasting plasma glucose test > 126mg/dL

  2. A two-hour oral glucose tolerance test > 200mg/dL

  3. A hemoglobin A1C >= 6.5%

If you do not have other symptoms of diabetes (ex. Thirst, weight loss, blurry vision, excessive urination), the diagnosis must be confirmed by repeating the same test you received on another day, unless you received two different tests (ex. A fasting plasma glucose test and a hemoglobin A1C test) that both are suggestive of diabetes.

Knowing When You Are At Risk Based on your results, your healthcare provider may also diagnose you with prediabetes. The current criteria for prediabetes are:

  1. A fasting plasma glucose test 100-125mg/dL

  2. A two-hour oral glucose tolerance test 140-199mg/dL

  3. A hemoglobin A1C 5.7-6.4%

If a diagnosis of prediabetes is established, these tests should be performed each year. Early detection of hyperglycemia is important to manage diabetes, and to prevent the progression of prediabetes to diabetes. Work with your healthcare provider to come up with a treatment plan that works best for you. This will usually involve dietary modifications, exercise, and in the case of a definitive diabetes diagnosis, medications to help control your blood sugar levels. References

  • American Diabetes Association. 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes-2021. Diabetes Care. 2021 Jan;44(Suppl 1):S15-S33. doi: 10.2337/dc21-S002. Erratum in: Diabetes Care. 2021 Sep;44(9):2182. PMID: 33298413.

  • National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes Tests & Diagnosis. 2016 Dec.

  • Centers for Disease Control and Prevention. Diabetes Tests. 2021 Aug.


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