Getting a diabetes test is straightforward: you can ask your primary care doctor for a blood test, walk into a retail clinic or independent lab, or even use an at-home kit. Most people will get one of three standard blood tests, all of which can detect both diabetes and prediabetes. If you have insurance, screening may be fully covered at no cost.
The Three Standard Tests
Doctors use three blood tests to diagnose diabetes, and any one of them can identify both full diabetes and prediabetes. The one your provider orders often depends on convenience, your health history, and whether fasting is practical for you.
The A1C test is the most convenient option. It measures your average blood sugar over the past two to three months by looking at how much sugar has attached to your red blood cells. No fasting required. An A1C below 5.7% is normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher means diabetes.
The fasting blood glucose test measures your blood sugar after you haven’t eaten for at least eight hours. Water is fine during the fast, but food, coffee, and other drinks are not. A result under 100 mg/dL is normal, 100 to 125 mg/dL falls in the prediabetes range, and 126 mg/dL or higher indicates diabetes.
The oral glucose tolerance test (OGTT) is the most involved. You fast for eight hours, give a blood sample, then drink a sugary solution containing 75 grams of glucose. Your blood is drawn again one hour and two hours later. A two-hour reading below 140 mg/dL is normal, 140 to 199 mg/dL is prediabetes, and 200 mg/dL or higher is diabetes. This test is commonly used during pregnancy screening but can be ordered for anyone.
Where to Get Tested
Your primary care doctor’s office is the simplest starting point. Mention that you’d like diabetes screening, and they’ll order the appropriate blood work. You may have your blood drawn right there or be sent to a nearby lab.
If you don’t have a regular doctor, retail clinics inside pharmacies like CVS MinuteClinic or Walgreens can run basic blood glucose or A1C tests. Independent labs such as Quest Diagnostics and Labcorp also let you order tests directly in many states, sometimes without a doctor’s referral. You book online, walk in, get your blood drawn, and receive results within a few days.
The cost without insurance is relatively low. An A1C test typically runs between $11 and $50 through discount lab services. A fasting glucose test is usually in the same range or less.
Insurance Coverage for Screening
Under the Affordable Care Act, all Marketplace health plans and many employer plans must cover type 2 diabetes screening with no copay, coinsurance, or deductible for adults aged 40 to 70 who are overweight or obese. This means the test is completely free if you meet those criteria. Even outside that specific category, most insurance plans cover diabetes blood work as part of routine lab panels, though you may owe a copay depending on your plan.
At-Home A1C Kits
At-home A1C kits are available at pharmacies and online. They use a finger prick instead of a vein draw, and you either read the result on a small device or mail the sample to a lab. Two products, Home Access and A1cNow+, are FDA-cleared for home use.
Accuracy varies significantly, though. In a University of Florida study of 219 people, the Home Access kit had 82% of its samples within 5% of a standard lab result. The A1cNow+ kit hit that same accuracy benchmark only 46% of the time. That gap matters: an inaccurately low reading could give you a false sense of security, while an inaccurately high one might cause unnecessary alarm. Home kits can be a useful starting point, especially for monitoring trends if you already have a diagnosis, but a lab-drawn test remains the gold standard for an initial diagnosis.
How to Prepare
If you’re getting an A1C test, there’s nothing special to do. Eat normally, drink normally, show up.
For a fasting blood glucose test or an OGTT, you need to fast for at least eight hours beforehand. Most people schedule these for first thing in the morning so the fasting period overlaps with sleep. You can drink water during the fast but should avoid food, juice, coffee, and tea. Ask your provider whether any medications you take should be paused before the test.
What Happens After One High Result
A single abnormal result doesn’t always lock in a diagnosis. In most cases, your doctor will order a second test, either the same type or a different one, to confirm the finding. For example, if your A1C comes back at 6.6%, you might be asked to repeat it or take a fasting glucose test. If two different tests both come back in the diabetes range, that confirms the diagnosis.
The exception is if you already have obvious symptoms of high blood sugar, like excessive thirst, frequent urination, and unexplained weight loss, combined with a random blood sugar reading of 200 mg/dL or higher. In that case, a single test can be enough.
When the A1C Test May Not Be Reliable
The A1C test works by measuring changes to red blood cells, so anything that affects those cells can throw off the result. If you have anemia, sickle cell disease, or another blood disorder, the A1C may read falsely high or low. Kidney failure and liver disease can also distort results. Certain medications, including some opioids and HIV treatments, may interfere as well. Pregnancy affects A1C accuracy, which is why the test isn’t used to screen for gestational diabetes (the OGTT is used instead).
If any of these apply to you, your provider will likely rely on fasting glucose or the oral glucose tolerance test rather than A1C.
Who Should Get Tested
The formal screening recommendation targets adults aged 40 to 70 who are overweight or obese, but several other factors warrant earlier testing. A family history of type 2 diabetes, a personal history of gestational diabetes, a sedentary lifestyle, or belonging to a higher-risk ethnic group (African American, Hispanic, Native American, Asian American, or Pacific Islander) all increase your risk. If you’ve been told you have prediabetes, repeat testing every one to three years helps track whether your blood sugar is staying stable, improving, or progressing toward diabetes.