Prediabetes Test / The Test for Prediabetes

The 1-minutes prediabetes quiz

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.

Testing for 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.

You can also determine your likelihood of having Prediabetes by completing the quiz below, which will tell you if you're at risk or not based on the CDC's point system. Think of it this way: Your risk increases if you:

• Are overweight (have a BMI of greater than 24)
• Have a family history of Diabetes (Type 2 )
• And about 10 other factors you can find out on the quiz.

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]

Principle

Fasting blood glucose is a test to determine "impaired fasting glucose" (IFG) as a sign of prediabetes.  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.

Prediabetes Test 2: Glycated Hemoglobin (A1C) [6]

Principle

You always have at least some glucose in your bloodstream. Because glucose is always in contact with your red blood cells, it can sometimes bind with, or attach to, them. More specifically, glucose binds with a component of your red blood cells called hemoglobin. The product is called "glycated hemoglobin," or "hemoglobin A1c."

The more glucose you have in your bloodstream, the more glucose binds with your hemoglobin. A higher percentage of your hemoglobin becomes glycated. While some glycated hemoglobin is normal, too much is a sign of a problem such as prediabetes or diabetes. High amounts of glycated hemoglobin can be a sign that other cells in your body, such as kidney cells, are becoming glycated. This can destroy them.

Glycated hemoglobin, hemoglobin A1c, HbA1c, and A1c all refer to the same test. The results are given in terms of percent (%) hemoglobin in your blood that has glucose molecules attached to it. 

How to Take It

The A1c test is a blood test. You can go at any time of the day, and it does not matter whether you are fasting or not. 

Results of the A1c Test

If your value is…Then…Under 5.7%

Your result is considered normal.

5.7-6.4%

You may have prediabetes.

6.5% or higher

You may have diabetes.

Pros and Cons

The A1c test is the most convenient test since you can take it at any time of the day, and you do not need to fast or prepare for it. It also has the advantage of giving you a three-month picture of what your blood sugar has been doing, rather than the instantaneous one-time shot that the FBG tells you. Finally, the A1c test has no daily variability, so your result will not change, for example, if you are short on sleep for a night, you are stressed, or you had a big meal the day before.

A drawback of A1c test is that it is more expensive than a FBG test. It may also be less accurate for as a prediabetes test than as a test for diabetes. In addition, A1c can be affected not only by your blood sugar levels (which is what we are interested in when talking about prediabetes), but also by factors related to your hemoglobin and red blood cells.

Prediabetes Test 3: Oral Glucose Tolerance Test (OGTT)

Principle

When you have a food or beverage with carbohydrates, your body breaks them down into glucose. The glucose enters your bloodstream, which raises blood glucose levels, which triggers insulin to be released from the pancreas to help lower your glucose levels back down.

In prediabetes and diabetes, you can have impaired glucose tolerance (IGT). Your body may have trouble bringing back your blood glucose levels to normal. This is what the OGTT measures. 

How to Take It

You need to begin the OGTT while you have been fasting for at least 8 hours or overnight. Your blood will be drawn. Then you will drink a solution that contains 75 grams of glucose. Your blood will be drawn at 1 and 2 hours after you drink the solution. 

Results of the OGTT

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

The OGTT is a more sensitive test than the A1c test. That means it is more likely than than the A1c test to detect prediabetes or diabetes if you have it; a "false negative" (saying you do not have prediabetes even when you actually do) is less likely.

The OGTT is more expensive than the A1c and FBG tests. Other drawbacks are that it is a bit more inconvenient and invasive.

• You need to begin with an 8-hour or overnight fast.
• You will need to get your blood drawn at least twice.
• You will need to dedicate 1, 2, or more hours to the test, and your clinic or lab may require you to stay on site while waiting for each blood draw.

Some people have trouble downing the required 75 grams of glucose. They may feel sick or nauseous. This amount of glucose is equivalent to the amount of sugar in 2 cans of regular (not diet) soda, or 2.5 bags of M&Ms.

Type 2 Diabetes Test: Random Blood Glucose

Principle

There is one more test that could come up, but it is more of a screening test for diabetes than prediabetes. The random plasma glucose (RPG) tests your glucose at any time. It could be high if your insulin sensitivity is low enough, or if you have little enough insulin, that your blood glucose levels never get down to healthy baseline levels. 

How to Take It

You can take the RPG at any time. You just need to go to a lab to get your blood drawn. 

Results of the RPG

If your value is…Then…Up to 199 mg/dl

Your blood sugar is considered normal.

Over 200 mg/dl

You may have diabetes.

Pros and Cons

The RPG is easy for you to take. You do not need to be fasting, and it can be done at any time of the day. It takes only one blood draw.

On the other hand, the RPG is not a good prediabetes test. It is likely to be used only when your doctor suspects that you have diabetes, or as a test to see whether you might need a FPG, A1c, or OGTT test. Your RPG can vary depending on time of day, stress level, whether you smoked or exercised, and other factors.

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.