Experts recommend screening for diabetes starting at age 45.
Testing for type 2 diabetes is crucial, since symptoms of type 2 diabetes often do not appear until blood sugar levels are already very high. That means you could live for months or years with type 2 diabetes and not even know it. It’s more common than you might think: one in four Americans with diabetes doesn’t actually know they have it, according to the Centers for Disease Control and Prevention.
“Patients with type 2 diabetes often don’t have any symptoms, and they’re diagnosed on routine blood testing,” says Sonal Chaudhry, MD, endocrinologist at NYU Langone Health.
Your doctor will want to check the following numbers to see whether you have type 2 diabetes.
Fasting blood glucose test: This number tests how much glucose is in the blood when you’re in a fasting state (usually at least eight hours), and this is included in routine blood tests. A fasting blood glucose equal to or greater than 126 may indicate type 2 diabetes, according to Minisha Sood, MD, endocrinologist in New York City.
A1C test: “This test measures your average blood sugar over the preceding two to three months,” says Dr. Chaudhry. An A1C level above 6.5 is consistent with type 2 diabetes. Learn more about the A1C test here.
Glucose tolerance test: In this test, doctors will record your fasting blood glucose, and then have you drink 75 grams of a glucose drink. After two hours, you’ll take a blood glucose test again and see how much glucose is still in the blood—or how well your body “tolerates” glucose. After the second test, a number above 200 mg/dL indicates type 2 diabetes.
It’s possible for one test to suggest you have type 2 diabetes and another to show “normal” results. That’s why doctors may do repeat tests to get a more accurate picture. Different tests results may mean you are in an early stage of type 2 diabetes and blood glucose levels are not consistently high, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
“The American Diabetes Association recommends that all patients over the age of 45 are screen for type 2 diabetes,” says Dr. Chaudhry. “If that screening is normal, then they should be screened at least every three years for diabetes.” (Here are other tests women need in their 40s and tests women need in their 50s.)
Of course, people with risk factors of type 2 diabetes—such as obesity or a family history of diabetes—should likely be tested earlier and more frequently. If you’ve already been diagnosed with prediabetes, you should get blood glucose levels checked again every one to two years, according to the American Diabetes Association.
Don’t wait until you’ve noticed symptoms of diabetes, which may not show up until the disease has progressed to an advanced state. “The earlier you find out, the earlier you’re able to work with your full team in order to manage the disease,” says Nesochi Okeke-Igbokwe, MD, internist in New York City.
An early diagnosis of diabetes has many benefits for your health, such as reducing the risk of serious complications. Learn how to protect your vision with diabetes, prevent foot problems with diabetes, and manage high and low blood sugar with diabetes.
Dr. Chaudhry is an endocrinologist at NYU Langone Health in New York City.Minisha Sood
Dr. Sood is a board-certified endocrinologist in private practice in New York City and an assistant professor at Hofstra School of Medicine.Nesochi Okeke-Igbokwe
Dr. Okeke-Igbokwe is an internist and health media expert in New York City.
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-: Patients with type 2 diabetes often don't have
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any symptoms and they're diagnosed on routine blood testing.
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Type 2 diabetes is diagnosed
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when your blood sugar is elevated.
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Doctors can assess your blood sugar
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in a number of different ways.
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-: There are a few diagnostic criteria that we keep in mind
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when diagnosing type 2 diabetes.
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One is a fasting plasma sugar, or fasting blood sugar.
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That's done on routine blood tests and if that number
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is equal to or greater than 126 on one or more occasions,
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then that goes along with type 2 diabetes.
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Sonal: One test is the hemoglobin A1C.
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This test measures your average blood sugar
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over the proceeding two to three months.
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If this number is higher than 6.5,
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it's consistent with type 2 diabetes.
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They may ask you to do a glucose tolerance test
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where they will measure your fasting blood sugar
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and then ask you to drink 75 grams of glucose
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and re-measure your glucose two hours later.
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If that glucose two hours later exceeds 200,
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that's also consistent with a diagnosis of diabetes.
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-: The American Diabetes Association recommends
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that all patients over the age of 45
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are screened for type 2 diabetes.
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If that screening is normal, then they should be screened
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at least every three years for diabetes.
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Patients who have risk factors for diabetes
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should be tested earlier and more frequently
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to make sure that they haven't developed type 2 diabetes.
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-: The earlier that you find out, the earlier you're able
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to work with your full team in order to manage the disease
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and make sure your blood sugar's always maintained
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at a steady level so that you don't progress
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to an advanced state.
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Diagnosing diabetes and learning about prediabetes. Arlington, VA: American Diabetes Association, 2014. (Accessed on May 5, 2021 at http://www.diabetes.org/diabetes-basics/diagnosis/.)
More than 29 million Americans have diabetes; 1 in 4 doesn’t know. Atlanta, GA: Centers for Disease Control and Prevention. (Accessed on May 5, 2021 at https://www.cdc.gov/media/releases/2014/p0610-diabetes-report.html.)
Olokoba AB, Obateru OA, Olokoba LB. Type 2 diabetes mellitus: a review of current trends. Oman Med J. 2012 Jul;27(4):269-73.The A1C test & diabetes. Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases. (Accessed on May 5, 2021 at https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis/a1c-test.)