Key Takeaways
Diabetes Screening
Diabetes screening is a set of blood tests used to detect elevated blood sugar levels before a person develops noticeable symptoms. It identifies both prediabetes — a reversible precursor condition — and Type 2 diabetes itself. Because diabetes often progresses silently for years, screening is the primary way to catch it early.
Screening differs from diagnostic testing in that it is applied to people without symptoms; a positive screening result typically requires confirmatory diagnostic testing before a clinical diagnosis is made.
Why Diabetes Screening Matters
An estimated 1 in 5 adults with diabetes in the United States does not know they have it, according to the Centers for Disease Control and Prevention (CDC). Prediabetes is even more underdiagnosed — approximately 80% of the 98 million American adults with the condition are unaware of it. This is not because the disease is rare or hard to detect; it is because Type 2 diabetes and prediabetes often cause no symptoms at all in their early stages.
Without screening, many people only discover elevated blood sugar levels after complications — such as nerve damage, kidney changes, or vision problems — have already begun to develop. Proactive testing changes that trajectory. Detecting prediabetes early, for instance, creates a meaningful opportunity to prevent or substantially delay the progression to Type 2 diabetes through evidence-based lifestyle modifications.
Diabetes screening fits into the broader framework of preventive care — tests designed to catch health conditions before they cause harm. See our overview of recommended health screenings by age and sex for context on where diabetes testing fits across a lifetime of preventive care.
~38%
U.S. adults with prediabetes
According to the CDC, approximately 98 million American adults have prediabetes — and about 80% are unaware of it.
1 in 5
Diabetes cases that go undiagnosed
The CDC estimates that roughly 8.5 million Americans living with diabetes have not yet received a diagnosis.
Up to 58%
Reduced progression risk with lifestyle changes
The NIH-funded Diabetes Prevention Program found structured lifestyle interventions reduced progression from prediabetes to Type 2 diabetes by up to 58%.
Who Should Be Screened
The U.S. Preventive Services Task Force (USPSTF) recommends screening for adults aged 35 to 70 who are overweight or obese (defined as a body mass index of 25 or higher). This reflects the strong relationship between excess body weight and insulin resistance, the underlying mechanism of Type 2 diabetes.
Beyond the USPSTF baseline, the American Diabetes Association and other clinical organizations identify additional risk factors that may warrant earlier or more frequent screening. These include:
- A first-degree relative (parent or sibling) with Type 2 diabetes
- History of gestational diabetes or delivering a baby weighing more than 9 pounds
- Polycystic ovary syndrome (PCOS)
- Being of African American, Hispanic/Latino, American Indian, Alaska Native, Asian American, or Pacific Islander heritage
- Physical inactivity
- High blood pressure or abnormal cholesterol levels
- Prior impaired fasting glucose result
If you are unsure whether you qualify for screening, a primary care provider can assess your individual risk profile and recommend an appropriate starting point.
Talk to Your Doctor About Your Risk Profile
Standard screening guidelines are a starting point, not a ceiling. If you have multiple risk factors — including family history, ethnicity, or a history of gestational diabetes — bring them up at your next appointment. Your provider can determine whether earlier or more frequent testing makes sense for you. Don't wait for symptoms to ask the question.
The Tests Used for Diabetes Screening
Three blood tests are most commonly used for diabetes screening. Each measures blood glucose in a different way, and each has specific preparation requirements.
Fasting Plasma Glucose (FPG)
This test measures blood sugar after an 8-hour fast. A result below 100 mg/dL is considered normal. A result between 100 and 125 mg/dL indicates prediabetes; 126 mg/dL or higher on two separate tests signals diabetes.
A1C (Glycated Hemoglobin) Test
The A1C reflects average blood glucose over approximately 2–3 months by measuring the percentage of hemoglobin coated with sugar. It requires no fasting, making it highly convenient. Normal is below 5.7%; the prediabetes range is 5.7%–6.4%; 6.5% or above on two separate tests indicates diabetes. Certain conditions affecting red blood cells — such as sickle cell anemia — can influence A1C accuracy, so your provider may choose a different test in those cases.
Oral Glucose Tolerance Test (OGTT)
Used less commonly for routine screening in adults (though standard in gestational diabetes evaluation), this test measures blood sugar before and two hours after drinking a glucose solution. It requires fasting beforehand. A 2-hour result of 140–199 mg/dL suggests prediabetes; 200 mg/dL or above points to diabetes.
A single abnormal result is generally not enough for a diagnosis. Confirmatory repeat testing is standard practice. Always discuss your results directly with your healthcare provider.
One Abnormal Result Is Not a Diagnosis
Clinical guidelines generally require a confirmed abnormal result on two separate occasions before a diagnosis of prediabetes or diabetes is made — unless symptoms are also present with a clearly elevated reading. If your first screening result is outside the normal range, your provider will arrange follow-up testing before drawing conclusions. Discuss any results directly with your healthcare team.
What Happens After Screening
A normal result is not a permanent clearance. If you have ongoing risk factors, your provider will likely recommend rescreening every one to three years. Consistent monitoring is important because risk factors and metabolic health can shift over time.
A prediabetes result, while concerning, is not a diabetes diagnosis — and it is genuinely actionable. Research, including the landmark Diabetes Prevention Program trial, has demonstrated that structured lifestyle changes (modest weight reduction and increased physical activity) can reduce the risk of progressing to Type 2 diabetes by up to 58% in people with prediabetes. The CDC-recognized National Diabetes Prevention Program offers structured support for exactly this purpose.
If results confirm Type 2 diabetes, your provider will discuss next steps, which may include lifestyle interventions, medication, and regular monitoring. Many of these preventive screenings are covered under health insurance — for details on how coverage generally works, see how preventive care screenings are typically covered under insurance.
If you are concerned about skipping screenings — whether due to cost, logistics, or the belief that feeling well means no testing is needed — common preventive care misconceptions addresses those barriers directly.
“The tragedy of Type 2 diabetes is that it is one of the most preventable serious chronic diseases, and yet millions of Americans are walking around with it undiagnosed. Screening is the bridge between not knowing and being able to act.”
— Centers for Disease Control and Prevention, U.S. public health agency, National Diabetes Statistics Report
This article provides general health information for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health or before making decisions about testing or care.