Most adults should start screening for diabetes at age 35 and retest every 3 years if results come back normal. If you have risk factors like obesity or a family history of diabetes, you may need to start earlier and test more often. The right schedule depends on your personal risk profile and whether previous results showed any warning signs.
The Standard Screening Schedule
Both the U.S. Preventive Services Task Force and the American Diabetes Association recommend that adults begin screening for prediabetes and type 2 diabetes at age 35. If your results are normal, retesting every 3 years is sufficient. This applies to people at average risk with no symptoms and no other conditions that would push them into a higher-risk category.
The every-3-years interval isn’t arbitrary. Type 2 diabetes develops gradually, often over years, and a 3-year window is short enough to catch the disease before complications set in but long enough to avoid unnecessary testing. That said, this timeline is a floor, not a ceiling. Your doctor may recommend more frequent checks depending on your initial results and overall health picture.
Risk Factors That Call for Earlier Testing
If you carry certain risk factors, waiting until 35 doesn’t make sense. The CDC identifies these as the major flags for prediabetes and type 2 diabetes:
- Overweight or obesity
- Age 45 or older
- A parent or sibling with type 2 diabetes
- Physical activity fewer than 3 times per week
- Non-alcoholic fatty liver disease
- A history of gestational diabetes or delivering a baby over 9 pounds
- Race and ethnicity: African American, Hispanic or Latino, American Indian, Alaska Native, some Pacific Islander, and some Asian American populations face higher risk
If any of these apply to you, screening before age 35 is reasonable, and your doctor may suggest testing every 1 to 2 years rather than every 3. The more risk factors you have, the more frequently you should be checked.
If You Have Prediabetes, Test Every Year
Prediabetes is the gray zone where your blood sugar is elevated but not high enough for a diabetes diagnosis. It shows up as an A1C between 5.7% and 6.4%, a fasting blood sugar between 100 and 125 mg/dL, or a two-hour glucose tolerance result between 140 and 199 mg/dL. About 1 in 3 American adults has prediabetes, and most don’t know it.
If you’ve been told you have prediabetes, the recommended retesting interval drops to once a year. The ADA and the Endocrine Society both recommend annual testing for anyone with prediabetes, because the progression to full diabetes can happen quickly, especially without lifestyle changes. Annual testing lets you and your doctor track whether diet, exercise, or other interventions are actually working to bring your numbers down.
After Gestational Diabetes
Women who develop diabetes during pregnancy face a significantly higher lifetime risk of type 2 diabetes. The recommended schedule is a two-step approach: get tested 6 to 12 weeks after delivery to check whether blood sugar has returned to normal, then screen every 3 years for the rest of your life. This postpartum screening is important because some women transition directly from gestational diabetes to type 2 without realizing it, particularly if they assume their blood sugar normalized after the baby was born.
Screening for Children and Teens
Type 2 diabetes in young people has risen sharply in recent decades. The ADA recommends risk-based screening for children starting at puberty or age 10, whichever comes first, if the child is overweight (BMI at or above the 85th percentile) and has at least one additional risk factor, such as a family history of type 2 diabetes or belonging to a higher-risk racial or ethnic group. If results are normal, retesting every 3 years is the standard. If the child’s BMI continues to climb, more frequent testing is warranted.
Certain Medications Increase Your Risk
Some commonly prescribed drugs can push blood sugar higher, and if you’re taking them, you may need more frequent monitoring than the general population. Steroids (glucocorticoids) are among the most well-known culprits. They tend to spike blood sugar after meals, so monitoring shouldn’t be limited to fasting glucose alone.
Certain antipsychotic medications, particularly olanzapine and clozapine, also carry significant diabetes risk. For people starting these drugs, annual fasting glucose checks are recommended at minimum. If you already have other risk factors, your doctor may check at 3 and 6 months after starting the medication. HIV protease inhibitors follow a similar pattern, with suggested screening every 3 months during the first year of use.
What the Tests Actually Measure
There are three main tests used to diagnose diabetes, and your doctor may use one or more of them. The A1C test measures your average blood sugar over the past 2 to 3 months. Normal is below 5.7%, prediabetes falls between 5.7% and 6.4%, and 6.5% or higher means diabetes. This test doesn’t require fasting, which makes it convenient for routine screening.
The fasting plasma glucose test measures blood sugar after at least 8 hours without eating. Normal is under 100 mg/dL, prediabetes is 100 to 125 mg/dL, and 126 mg/dL or above indicates diabetes. The oral glucose tolerance test measures how your body handles a sugary drink over two hours. Normal is under 140 mg/dL, prediabetes is 140 to 199 mg/dL, and 200 mg/dL or higher is diabetes.
One important caveat: the A1C test isn’t reliable for everyone. People with sickle cell trait, other hemoglobin variants, or significant iron deficiency anemia can get misleading A1C results. In late pregnancy, A1C readings can also run artificially high. If any of these apply to you, your doctor should use a glucose-based test instead.
Symptoms That Warrant Immediate Testing
Screening schedules are designed for people who feel fine. If you’re experiencing symptoms, don’t wait for your next scheduled test. The classic warning signs of diabetes include excessive thirst, frequent urination, unexplained weight loss, persistent fatigue, blurry vision, and slow-healing infections (particularly of the skin, gums, or vaginal area). These symptoms can appear gradually with type 2 diabetes or come on rapidly with type 1. Either way, they call for prompt testing regardless of when you were last screened or how old you are.