Diabetes Screening: Who Gets Tested, What It Measures, and What Comes Next

Who Should Get Screened — and When

The USPSTF recommends blood sugar screening for adults aged 35 to 70 who are overweight or obese — defined as a BMI of 25 or higher. The American Diabetes Association (ADA) casts a wider net, recommending screening beginning at age 45 for all adults, and earlier for anyone with additional risk factors.

Those risk factors include:

• A first-degree relative (parent or sibling) with diabetes
• A personal history of gestational diabetes or polycystic ovary syndrome
• High blood pressure or abnormal cholesterol levels
• Belonging to a higher-risk ethnic group, including Black, Hispanic, Asian American, and American Indian populations
• A sedentary lifestyle

If your last results were normal and no new risk factors have emerged, most guidelines suggest rescreening every three years. For people with prediabetes, annual monitoring is more appropriate. This is part of a broader preventive picture — see how recommended screenings evolve across decades for context on how diabetes testing fits into your overall health schedule.

What the Tests Actually Measure

Two tests form the backbone of diabetes screening in the U.S., and understanding what each measures helps you make sense of your results.

Fasting Plasma Glucose (FPG)

This test measures blood sugar after an 8-hour fast. It captures your baseline glucose — how well your body manages blood sugar when it hasn't been stimulated by food. A reading below 100 mg/dL is normal. Between 100 and 125 mg/dL indicates prediabetes (called impaired fasting glucose). At 126 mg/dL or higher on two occasions, diabetes is typically diagnosed.

Glycated Hemoglobin (A1C)

The A1C test measures the percentage of hemoglobin — the protein in red blood cells — that has glucose attached to it. Because red blood cells live roughly three months, A1C reflects average blood sugar over that period, not a single-day snapshot. No fasting is required. A result below 5.7% is normal; 5.7–6.4% signals prediabetes; 6.5% or above on repeat testing indicates diabetes.

Some providers also use an oral glucose tolerance test (OGTT), which measures blood sugar two hours after drinking a glucose solution — this is particularly common in pregnancy screening. Understanding how these numbers connect to your body's energy regulation is covered in our metabolism literacy checklist.

Understanding Results in the Gray Zone

A prediabetes result is one of the most actionable findings in preventive medicine — and one of the most commonly misunderstood. It does not mean diabetes is inevitable. Research consistently shows that structured lifestyle interventions can reduce the risk of progressing from prediabetes to type 2 diabetes by a meaningful margin.

The CDC's National Diabetes Prevention Program (DPP), based on landmark clinical trial data, found that modest, sustained changes — primarily increased physical activity and modest weight reduction in those who were overweight — reduced diabetes progression risk significantly compared to a control group. These are population-level findings, not individual guarantees, and outcomes vary.

If your numbers land in the prediabetes range, your provider may recommend:

• Repeat testing in 6–12 months to confirm and track the trend
• Referral to a structured diabetes prevention program
• Dietary pattern adjustments reviewed with a registered dietitian
• Increased physical activity, tailored to your current fitness level

Other preventive screenings — like blood pressure checks and cholesterol testing — are often reviewed alongside blood sugar results, since these conditions frequently cluster together as part of metabolic syndrome.

This article is for general informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for guidance specific to your health situation, symptoms, or test results.