Testing for Prediabetes 101

Testing for Prediabetes 101

Prediabetes is one of the most common conditions in the country today. The Centers for Disease Control and Prevention (CDC) report that over one-third of Americans 18 or over had prediabetes in 2015[1]. That includes 84.1 million people, and the numbers are only increasing.

Why should you care?

  • One of those people could be you.

  • Diabetes is not just your grandmother’s disease. One in 12 Americans 44 years or younger has prediabetes, and 1 in 25 Americans in that age group have diabetes.

  • Prediabetes is a risk factor for type 2 diabetes and serious complications that can follow, and knowing that you have prediabetes can better enable you to prevent the consequences.

Do I Have Prediabetes?

The only way to find out for sure is getting tested. A prediabetes test is quick and simple. Your doctor can order one, and you can get it done where you normally get your blood drawn for cholesterol and other routine tests.


Why Test for Prediabetes?

Why should you test for prediabetes? Wouldn’t you know if you have it? Actually, not necessarily. In fact, you are unlikely to notice any symptoms of prediabetes, although a minority of prediabetes patients do notice a darkening of skin on the back of their neck, in the groin area, or under their armpits. The condition is called acanthosis nigricans[2].

The only way to know for sure if you have prediabetes is to get tested. While 1 in 3 American adults has prediabetes, only 11.6%, or 1 in 9, of people with prediabetes, report that their doctor has told them that they have prediabetes. The other 74 million prediabetes patients are unaware that they have it.

You may be worried about your test result, but getting tested for prediabetes is better than not being tested. If you know you have prediabetes, you can take steps to manage your condition and prevent or delay type 2 diabetes and complications.

Prediabetes Testing 101

Prediabetes is a condition in which your body has trouble keeping your blood sugar, or blood glucose, within normal ranges. It happens as the cells in your body become resistant to the effects of a hormone called insulin. 

Your pancreas release insulin when you eat foods with carbohydrates and your blood sugar levels rise. The insulin helps cells in your body remove glucose from your bloodstream and take it into the cells. If you develop insulin resistance, you need more insulin to keep your blood glucose levels normal. Eventually, your insulin production cannot meet the increasing demands for insulin, and your blood sugar levels rise – that is when prediabetes can be diagnosed.

With prediabetes, your blood glucose is higher than normal, and lower than in diabetes. These are the tests that your doctor can use to diagnose prediabetes or type 2 diabetes[3].

  • Fasting blood glucose (FBG)

  • Glycated hemoglobin (A1C)

  • Oral glucose tolerance test (OGTT)

  • (for diabetes only) random blood glucose (RBG)

The National Institute for Diabetes and Digestive and Kidney Disorders (NIDDK) explains that your doctor may ask you to repeat the test if the first one suggests that you have prediabetes or diabetes. Testing a second time can confirm the results of your first prediabetes test.

Prediabetes Test 1: Fasting Blood Glucose (FBG)[4]


Fasting blood glucose is a test to determine “impaired fasting glucose” (IFG) as a sign of prediabetes.[5]  After you eat a meal or snack with carbohydrates or calories, your blood sugar levels rise. In response, your pancreas secrete insulin, which should help the fat, liver, and muscle cells in your body take up sugar from the blood. The result is that your blood sugar levels should then fall, fairly quickly, back to baseline, or fasting, levels. The FBG test measures your blood glucose at these low points, long after a meal.

How to Take It

You need to fast for at least 8 hours. That means you cannot have any food or drink with calories. Water is fine. Usually, your doctor will suggest that you fast overnight and go to the lab in the morning, before you eat anything. The nurse or lab technician will draw your blood. 

Results of the FBG Test

If your value is… Then…
Under 100 mg/dl
Your result is considered normal.
100-125 mg/dl
You may have prediabetes.
Over 125 mg/dl
You may have diabetes.


Pros and Cons

You can get a fasting blood sugar test pretty much anywhere that you can get your blood drawn – it is a common test. This test is relatively inexpensive, which is great if your insurance is less than comprehensive.

Some people have trouble with this test because they are hungry in the morning and want breakfast. Even more difficult can be your doctor’s order to abstain from drinking coffee or having another source of caffeine until you take your test.

Another caveat with an FBG is that your blood glucose levels can fluctuate day to day, and even minute to minute. The single blood draw only shows what is happening in your blood at that one point in time, whereas in reality, your levels could change for a variety of reasons, such as if you exercised intensely the evening before, or if you are a little bit ill.

After Your Prediabetes Test

Follow up with your doctor when you get the results of your prediabetes test. Your doctor can tell you what the results mean. The likely possibilities are:

  • Everything is fine for now – good job!

  • You need another prediabetes test to confirm the results of the first test.

  • You have prediabetes.

Continued Blood Sugar Testing

You will need another prediabetes test at some point. If you do not have prediabetes now, your next test may be within another 2 to 5 years, depending on your risk factors and your healthcare provider’s recommendation. 

If you do have prediabetes, your healthcare provider will tell you how often to retest your blood sugar. The ongoing tests will let you know how well your prediabetes management plan is working. You may get your blood sugar tested every year or more often.

Consider a Diabetes Prevention Program (DPP)

If you have prediabetes, you can work to lower your blood sugar levels with healthy lifestyle changes. Losing extra weight, increasing physical activity, and improving your diet can all be effective. They can delay the onset of type 2 diabetes, prevent it altogether, or even reverse prediabetes.

The CDC-recognized Diabetes Prevention Program (DPP) is a proven strategy for implementing these changes. A DPP may be covered by your health insurance. It includes a year-long curriculum that you can cover in in-person meetings or through a digital DPP, such as Lark. Lark is available on your smartphone and it includes coaching on prediabetes and other aspects of health.