Getting tested for diabetes is straightforward: you need a blood test ordered by a doctor or, in some cases, purchased at a pharmacy. The most common screening tests are a fasting blood sugar test, an A1C test, or an oral glucose tolerance test, and any of them can be done in a single office visit. Here’s what to expect from each option and how to know if you should get tested now.
Who Should Get Tested
The American Diabetes Association recommends routine diabetes screening for all adults starting at age 35, regardless of weight or symptoms. If you’re under 35 but overweight or obese and have at least one additional risk factor, screening is also recommended. Those risk factors include high blood pressure, abnormal cholesterol levels, a family history of diabetes in a parent or sibling, or a personal history of gestational diabetes.
Certain symptoms should prompt testing right away, no matter your age or weight. These include frequent urination, unusual thirst or hunger, unexplained weight loss, fatigue, blurry vision, and recurring yeast infections or urinary tract infections. Type 2 diabetes can also cause slow-healing cuts, numbness or tingling in the hands and feet, and dark patches of skin around the neck, armpits, or groin. In children, new bedwetting or increased accidents can be an early sign of type 1 diabetes. If you’re experiencing several of these symptoms together, don’t wait for a routine screening.
The Three Main Diagnostic Tests
Fasting Blood Sugar Test
This is the simplest and most widely used test. You fast for 8 to 12 hours beforehand (water is fine), then have your blood drawn. Your provider will tell you the exact fasting window. A result below 100 mg/dL is normal. Between 100 and 125 mg/dL indicates prediabetes. A result of 126 mg/dL or higher points to diabetes.
A1C Test
The A1C measures your average blood sugar over the past two to three months, which makes it useful for seeing the bigger picture rather than a single snapshot. No fasting is required, so it can be done at any time of day. A normal A1C is below 5.7%. Between 5.7% and 6.4% means prediabetes. An A1C of 6.5% or higher indicates diabetes.
Oral Glucose Tolerance Test
This test measures how your body handles a large dose of sugar. After fasting for at least 8 hours, you’ll have your blood drawn, then drink a liquid containing 75 grams of glucose. Your blood is drawn again one and two hours later. A two-hour result below 140 mg/dL is normal. Between 140 and 199 mg/dL is prediabetes. A reading of 200 mg/dL or above means diabetes. This test takes at least two hours in the office and is less commonly used for routine screening, but it’s the standard method for diagnosing gestational diabetes.
There’s also a random blood sugar test, which can be done at any time without fasting. If your blood sugar comes back at 200 mg/dL or above and you have classic symptoms like extreme thirst, frequent urination, or unexplained weight loss, that single result is enough for a diagnosis. In most other cases, your doctor will confirm an initial positive result with a second test on a different day.
Testing During Pregnancy
Most pregnant women are screened for gestational diabetes between 24 and 28 weeks. The most common approach in the U.S. is a two-step process. In the first step, you drink a glucose solution and have your blood drawn one hour later. No fasting is needed for this initial screen. If your blood sugar comes back too high, you return for a longer follow-up: a three-hour glucose tolerance test that requires fasting and involves four blood draws (before drinking the solution and at one, two, and three hours after).
Some providers use a one-step approach instead, which is a single two-hour test with fasting and three blood draws. Your OB or midwife will let you know which protocol they use. If you had gestational diabetes in a previous pregnancy or have other risk factors, your provider may screen you earlier than 24 weeks.
How to Prepare
If your test requires fasting, don’t eat or drink anything besides water for the window your provider specifies, typically 8 to 12 hours. Most people schedule a fasting test first thing in the morning so the fast happens overnight. Let your provider know about any medications you’re taking, as some can affect blood sugar results. The A1C and random blood sugar tests don’t require any preparation at all.
Where to Get Tested
The standard path is to ask your primary care doctor for a screening. They’ll order blood work that you can get done at the office or at a nearby lab. If you don’t have a primary care provider, urgent care clinics and community health centers can order the same tests. Some pharmacies and retail clinics offer A1C screenings as well.
Home A1C kits are available over the counter and can give you a general sense of where you stand, but their accuracy varies widely. A University of Florida study comparing home kits to standard lab results found that one FDA-cleared home test (Home Access) had 82% of its samples within the accepted accuracy range, while another FDA-cleared test (A1cNow+) met that benchmark only 46% of the time. Home kits can be useful for monitoring trends between doctor visits, but they aren’t a substitute for a lab-confirmed diagnosis.
What Testing Costs
Under the Affordable Care Act, most private insurance plans cover diabetes screening with no out-of-pocket cost when your doctor determines you’re at risk. Medicare Part B covers up to two blood glucose screenings per year for people with risk factors like high blood pressure, obesity, abnormal cholesterol, or a history of high blood sugar. You also qualify for Medicare-covered screenings if at least two of the following apply: you’re 65 or older, you’re overweight, you have a family history of diabetes, or you have a history of gestational diabetes or delivering a baby weighing more than 9 pounds.
Without insurance, a fasting glucose test or A1C test at a lab typically costs between $10 and $50. An oral glucose tolerance test runs higher because of the multiple blood draws. Community health centers often offer sliding-scale pricing based on income.
What Happens After Your Results
If your results fall in the normal range, you won’t need another screening for three years unless your risk factors change. A prediabetes result means your blood sugar is elevated but not yet at the diabetes threshold. At this stage, modest lifestyle changes (losing 5% to 7% of your body weight, increasing physical activity) can significantly reduce your risk of progressing to type 2 diabetes, and your doctor will likely recommend repeat testing every one to two years.
A result in the diabetes range will usually be confirmed with a second test before you receive a formal diagnosis, unless your blood sugar is very high or you already have clear symptoms. From there, your provider will discuss a management plan, which for type 2 diabetes often starts with dietary changes and exercise before adding medication. For type 1 diabetes, insulin therapy begins right away. Either way, the earlier you catch it, the more options you have for keeping blood sugar under control and avoiding complications down the road.