When Should You Get Tested for Type 2 Diabetes?
Know your risk, testing options and what results mean
Know your risk, testing options and what results mean
Key Takeaways
- Diabetes can develop without symptoms.
- Most adults should start screening at age 35.
- Your risk factors may call for earlier testing.
- Blood tests can detect prediabetes and diabetes.
- If you have prediabetes, get tested for type 2 diabetes every year.
You can have prediabetes or type 2 diabetes and not know it. That’s because both can develop without obvious symptoms. Knowing your risk and when to check your blood sugar can help you catch problems early.
“Type 2 diabetes often begins as prediabetes, a condition where blood glucose levels are higher than normal, but not yet elevated enough to qualify as diabetes,” says Athena Philis-Tsimikas, MD, an endocrinologist at Scripps Clinic and corporate vice president of the Scripps Whittier Diabetes Institute.
Type 2 diabetes accounts for about 90% to 95% of diabetes cases, according to the Centers for Disease Control and Prevention. Unlike type 1 diabetes, an autoimmune condition, type 2 develops when the body doesn’t use insulin well or make enough to keep blood sugar in a healthy range.
A simple blood test can detect prediabetes or diabetes early and help you and your doctor decide what steps to take next.
Who should be screened for type 2 diabetes?
For adults without other reasons to test earlier, the American Diabetes Association recommends diabetes screening starting at age 35.
“You may need diabetes screening before age 35 if you have certain risk factors. Your doctor can look at your family history, weight, blood pressure and other factors to determine when testing should start,” Dr. Tsimikas says.
Risk factors include:
- Having a parent or sibling with diabetes
- Having high blood pressure or abnormal cholesterol levels
- Having a history of gestational diabetes (diabetes during pregnancy)
- Having polycystic ovary syndrome (PCOS)
- Being physically inactive
- Having a history of heart disease
Type 2 diabetes is also more common among certain racial and ethnic populations, including Black, Hispanic or Latino, American Indian, Alaska Native, Asian American and Pacific Islander populations.
Ask about testing sooner if you develop possible symptoms, such as increased thirst, frequent urination, unexplained weight loss or unusual fatigue. Don’t wait for your next routine screening if you notice these changes. Learn more about early signs of type 2 diabetes and when to talk with your doctor.
How often should you get tested for diabetes?
How often you need diabetes screening depends on your test results and risk factors.
The American Diabetes Association recommends:
- Normal screening results: Get tested at least every three years, or sooner if your risk factors change or you develop symptoms.
- Prediabetes: Get tested every year for type 2 diabetes.
- History of gestational diabetes: After postpartum screening, continue testing every one to three years, even if your results return to normal.
Your doctor can recommend a screening schedule based on your health and previous results.
What tests are used to screen for diabetes?
Three common blood tests can help detect prediabetes and diabetes.
1. Hemoglobin A1C test
The A1C test measures your average blood sugar level over the past three months. It measures the percentage of hemoglobin, a protein in red blood cells, that has glucose attached to it. A higher percentage generally means a higher average blood sugar level. You don't need to fast before an A1C test.
Certain conditions that affect red blood cells or hemoglobin, including some forms of anemia, can make A1C results less reliable. Your doctor may recommend another test if A1C is not appropriate for you.
2. Fasting plasma glucose test
The fasting plasma glucose (FPG) test measures your blood sugar after you have gone at least eight hours without food or caloric drinks. Water is allowed. The test is usually done in the morning after an overnight fast.
3. Oral glucose tolerance test
The oral glucose tolerance test (OGTT) measures how your body processes glucose. Your doctor may recommend this test when more information is needed about how your body processes glucose.
After fasting overnight, you’ll have your blood drawn to measure your blood sugar. You’ll then drink a beverage containing glucose and have your blood sugar checked again two hours later.
The OGTT is also used to test for gestational diabetes, although testing procedures and diagnostic ranges during pregnancy are different.
What do your blood sugar test results mean?
Your blood sugar results can show whether your levels are normal, indicate prediabetes or fall within the diabetes range.
The following ranges apply to adults who are not pregnant.
Hemoglobin A1C test
- Normal: Below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
Fasting plasma glucose test
- Normal: Below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
Oral glucose tolerance test (2-hour result)
- Normal: Below 140 mg/dL
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or higher
If your results fall within the prediabetes range, your blood sugar is higher than normal, which increases your risk of developing type 2 diabetes.
Your doctor can review your results and explain what they mean for your health.
What happens if your blood sugar test is abnormal?
A result within the diabetes range doesn't always mean you have diabetes.
“An abnormal result is the beginning of a conversation, not always the final diagnosis. Your doctor may repeat the test or use another test to confirm what your blood sugar levels mean,” Dr. Tsimikas says.
In most cases, a diabetes diagnosis requires two abnormal test results. However, repeat testing may not be necessary if you have classic diabetes symptoms and a random plasma glucose level of 200 mg/dL or higher.
Your next steps will depend on your results.
- If you have normal blood sugar: Your doctor can recommend when you should be tested again based on your risk factors.
- If you have prediabetes: Lifestyle changes and regular testing can help manage your blood sugar and lower your risk of developing type 2 diabetes. Learn more about how to prevent type 2 diabetes.
- If you have diabetes: Your doctor will work with you to develop a treatment plan, which may include lifestyle changes, medication, regular follow-up and blood sugar monitoring.
Talk with your doctor about diabetes screening
You don’t need to wait for symptoms to get your blood sugar checked. If you’re 35 or older, or have risk factors for type 2 diabetes, ask your primary care doctor when screening is right for you.
Your annual physical exam is a good time to review your risk factors, discuss diabetes screening and determine which tests may be right for you.