You can check for diabetes through a simple blood test ordered by your doctor, but the signs your body gives you beforehand often point you in the right direction. A fasting blood sugar of 126 mg/dL or higher on two separate tests confirms a diabetes diagnosis, while levels between 100 and 125 mg/dL indicate prediabetes. Here’s how to recognize the warning signs, understand the tests, and know what your results mean.
Symptoms That Should Prompt Testing
Both type 1 and type 2 diabetes share a core set of symptoms: frequent urination, increased thirst and hunger, unexplained weight loss, fatigue, irritability, blurry vision, and frequent urinary tract or yeast infections. These overlap because both types involve blood sugar that your body can’t properly use, though the underlying cause differs.
Type 1 diabetes often comes on quickly and can include nausea, vomiting, and stomach pain. In children, unexplained bed-wetting or increased bathroom accidents can be an early signal. Type 2 diabetes tends to develop gradually, sometimes over years, and brings its own additional clues: cuts or sores that heal unusually slowly, numbness or tingling in your hands and feet, and dark, velvety patches of skin around the neck, armpits, or groin.
Those dark patches, called acanthosis nigricans, deserve special attention. They’re a visible sign of insulin resistance, which means your body is struggling to process sugar even before blood sugar levels climb high enough for a diabetes diagnosis. If you notice them, it’s worth getting tested even if you feel fine otherwise.
Who Should Get Screened Without Symptoms
You don’t need to have symptoms to get tested. Both the American Diabetes Association and the U.S. Preventive Services Task Force recommend that adults begin screening at age 35 if they are overweight or obese, then repeat every three years. The ADA also recommends screening for any adult with overweight or obesity who has at least one additional risk factor, such as a family history of diabetes, a sedentary lifestyle, a history of gestational diabetes, or belonging to a higher-risk ethnic group (African American, Hispanic, Native American, Asian American, or Pacific Islander).
Pregnant individuals who haven’t previously been diagnosed are typically screened for gestational diabetes between 24 and 28 weeks of pregnancy using a glucose tolerance test.
The Three Main Diagnostic Tests
Fasting Blood Sugar Test
This is the most straightforward test. You fast for at least eight hours (usually overnight), then have your blood drawn. A result below 100 mg/dL is normal. Between 100 and 125 mg/dL is prediabetes. At 126 mg/dL or higher on two separate tests, you have diabetes. Your doctor will almost always confirm an elevated result with a second test on a different day before making a diagnosis.
A1C Test
The A1C measures your average blood sugar over the past two to three months, expressed as a percentage. It doesn’t require fasting, which makes it convenient. A normal A1C is below 5.7%. Between 5.7% and 6.4% is prediabetes. At 6.5% or higher, it indicates diabetes. This test captures the bigger picture of your blood sugar control rather than a single snapshot.
Oral Glucose Tolerance Test
This test is more involved but gives a detailed look at how your body handles sugar. You fast for eight hours, then drink a solution containing 75 grams of sugar. Your blood is drawn at the one-hour and two-hour marks. At the two-hour mark, a reading below 140 mg/dL is normal. Between 140 and 199 mg/dL signals prediabetes. A reading of 200 mg/dL or higher suggests diabetes. This test is commonly used during pregnancy screening and when results from other tests are borderline.
Can You Test at Home?
Over-the-counter blood glucose monitors, the kind you prick your finger to use, can give you a general sense of where your blood sugar stands. But they’re not designed for diagnosis. These monitors are considered accurate if they fall within 15% of a laboratory reading, which means a true blood sugar of 126 mg/dL could show up anywhere from 107 to 145 on a home device. That’s a wide range that spans from normal to clearly diabetic.
Dehydration, anemia, and testing on alternate sites like the forearm instead of the fingertip can further throw off accuracy. A home monitor showing a consistently high number is a strong reason to see your doctor, but a normal-looking number doesn’t rule diabetes out. Only a lab-grade blood test can confirm or exclude a diagnosis.
Type 1 vs. Type 2: How Doctors Tell Them Apart
The blood sugar tests above confirm that you have diabetes, but they don’t tell you which type. Type 1 is an autoimmune condition where the immune system destroys the cells that produce insulin. Type 2 is a metabolic condition where the body becomes resistant to insulin or doesn’t make enough. The distinction matters because treatment is different.
When the type isn’t obvious from your age, symptoms, and health history, doctors can order autoantibody tests. These look for immune system markers that attack insulin-producing cells. A panel typically checks for four specific antibodies, and finding multiple positives strongly suggests type 1 diabetes. Negative results don’t completely rule it out, but they make type 2 far more likely. A separate test measuring how much insulin your body still produces can provide additional clarity.
What Prediabetes Results Mean
If your numbers land in the prediabetes range, that’s not just a warning label. About 80 million adults in the U.S. have prediabetes, and without changes, a significant portion will progress to type 2 diabetes within five to ten years. The good news is that prediabetes is the stage where lifestyle changes have the most impact. Losing 5% to 7% of your body weight and getting 150 minutes of moderate physical activity per week can cut your risk of developing type 2 diabetes by more than half.
Your doctor will likely recommend retesting in one to three years depending on your other risk factors. In the meantime, pay attention to any skin changes, increasing thirst, or shifts in how often you urinate, as these could signal progression.
What Happens After a Diabetes Diagnosis
A confirmed diagnosis doesn’t mean figuring everything out alone. Your doctor will typically refer you to a diabetes care and education specialist who helps you build a management plan tailored to your lifestyle, health needs, and food preferences. These specialists are part of diabetes self-management education and support programs, which teach you the practical skills for day-to-day management: how to monitor your blood sugar, what to eat, how to stay active, and how to recognize when something is off.
Early follow-up usually includes a comprehensive eye exam, a check of kidney function, a foot exam, and blood work looking at cholesterol and other cardiovascular risk factors. Diabetes affects blood vessels and nerves throughout the body, so establishing baseline measurements helps your care team catch complications early. Most people also begin working on a meal plan with their specialist, which is less about restriction and more about understanding how different foods affect blood sugar so you can make informed choices.