Pre-Diabetes: What Is It, Do I Have It, and How Do I Stop It?

Ryan Bradley, ND, MPH     March 2009


“Pre-diabetes” is the term used to identify people who are at great risk of developing type 2 diabetes. There is a lot of confusion over the term pre-diabetes which, unfortunately, is frequently used inaccurately by individuals and their doctors. Pre-diabetes is important to detect early, and it is equally important to know when pre-diabetes has progressed to actual diabetes. In this article I will define pre-diabetes formally, and also describe the proven methods for preventing diabetes, once pre-diabetes has been detected.

What is pre-diabetes?

Frequently I see patients who have been told by their doctors that they have pre-diabetes or “early” diabetes. What I have found in practice is the terms “pre-diabetes” and “early” diabetes are often used to try and comfort or protect patients from learning they have frank diabetes; many patients are no longer “pre”, but in fact have diabetes. I find the term pre-diabetes misleading, as it implies a state before the disease really gets started; this is an unfortunate designation because pre-diabetes is really an earlier stage in the disease continuum - some damage has already been done!

Pre-diabetes has two formal definitions. One definition for pre-diabetes is having a blood sugar reading between 100 and 125 mg/dl in the fasting (i.e. no food for 10-12 hours) state (1). This type of pre-diabetes is called “impaired fasting glucose” or IFG.

The other definition is based on doing an oral glucose tolerance test (OGTT); an OGTT involves drinking a sugary solution and testing blood sugar once per hour for several hours following the beverage. Based on an OGTT, pre-diabetes is defined as having a blood sugar between 150 and 199 mg/dl 2-hours after the test.1 This type of pre-diabetes is called “impaired glucose tolerance” or IGT.

Why would you do an OGTT if you can tell based on a simple blood test?

Different people can present with pre-diabetes differently, depending on which tissues in the body become resistant to insulin first. If the liver becomes resistant to insulin first, then a fasting blood test is enough. If the muscles become resistant to insulin first, then an OGTT may be necessary to know for sure whether pre-diabetes is present. How do you know, which comes first? Well we do not always know, but we do know that people from some ethnic backgrounds, including Black Americans, Latino Americans and Asian Americans, may develop IGT before IFG.

Won’t drinking the sugar beverage for the OGTT do more harm than good?

I think this is a common misconception. If you are hesitant to complete an OGTT, start reviewing beverages in your local store, and you’ll quickly learn how common it is for drinks to have well in excess of the 75 grams of sugar used in an OGTT; many drinks, even juices, often have between 35-40 grams of sugar per serving, and thus you may be doing an OGTT more frequently than you know!

Can I get a hemoglobin A1c test to tell if I have pre-diabetes?

Although the hemoglobin A1c (HbA1c) test is used to monitor blood sugar over longer periods of time, it is not the definitive test for detecting pre-diabetes. That said, if you receive an abnormal HbA1c test - say greater than 6-6.5% - then pre-diabetes is highly likely.

How common is pre-diabetes & how do I find out if I have it?

The American Diabetes Association estimates that 57 million people in the United States have pre-diabetes, or approximately 19% (1/5) of the population! (2) Unfortunately, it is estimated that up to 50% of these people do not know they have the condition.

Testing for pre-diabetes is easy, and the first step requires only a fasting blood test at your doctor’s office. If you are a member of an ethnic group at higher risk for developing impaired glucose tolerance (see above), then you should ask to schedule an OGTT instead of just a fasting blood test.

Home glucometers should not be used to try and test for pre-diabetes at home because at your doctor’s office the blood sugar is tested from blood in your veins, which is slightly different from the blood in the small capillaries you use with a home glucometer. Also home glucometers have a lot of variability in their readings day-to-day and even minute-to-minute. If you are going to test for pre-diabetes, it is better to make the test more definitive.

Why is finding out about pre-diabetes important?

The obvious answer is that finding out about pre-diabetes is important so that you can take steps to prevent developing full-blown diabetes. Because type 2 diabetes greatly contributes to the risk of developing heart disease, kidney disease requiring dialysis, adult-onset blindness and amputation, identifying risk for diabetes, and preventing diabetes is very important for your long-term health.

Type 2 diabetes is preventable. The Diabetes Prevention Program (DPP) was a 3-year clinical trial that definitively showed type 2 diabetes can be prevented by losing weight and adopting a healthier lifestyle (3). The DPP compared lifestyle changes to the drug metformin for preventing type 2 diabetes. Although metformin also prevented diabetes, lifestyle changes were far more effective than the drug approach; metformin reduced the rate of diabetes by 31%, whereas lifestyle changes reduced the rate by 58%!

In the absence of lifestyle changes, the majority of people who develop pre-diabetes will continue on to develop type 2 diabetes. Even if medications are used in the short-term to prevent diabetes, what happens in 3-5 years when the medication isn’t working anymore? The progression of diabetes is well established; the disease does not simply plateau, rather it continues to worsen, requiring more and more medication, and ultimately insulin injections.

How was diabetes prevented in the DPP?

Diabetes was prevented in the DPP by altering the diet of participants and increasing exercise levels. The two main goals of the DPP intervention were to lose and maintain 7% of the participants’ body weight and to increase physical activity in participants to the recommended 150 minutes per week (4). When the results were analyzed, weight loss during the study was the greatest predictor of preventing diabetes; for every 2.2 pounds of weight loss, there was a corresponding reduction in risk for diabetes of 16%, or almost a 60% reduction for each 11 pounds of weight lost (5). In the DPP, meeting exercise goals of 150 minutes per week and reducing food calories that come from fat in the diet were both predictors of reaching the weight loss goals set in the study (5).

Be warned, the medical literature questions whether or not giving lifestyle recommendations to patients in primary care is worth the time and money (6), so you may need to find better sources for nutrition and exercise information than your family medical doctor. Visit the American Associations of Naturopathic Physicians website to find a licensed, accredited naturopathic physician in your region, or find a registered dietician through the American Dietetics Association to help with dietary change.

Are there foods or supplements that I can use to prevent diabetes?

Let’s by answering the easier question, there are no nutritional supplements that have been shown to prevent type 2 diabetes. There is considerable research showing beneficial effects of supplements in the treatment of diabetes and various complications of diabetes, however none of these supplements have been thoroughly tested for diabetes prevention. Because the prevention of type 2 diabetes is so important, I do not count on supplements to do the work my patients need to do to change their lifestyles and lose weight (much to their disappointment sometimes!).

Regarding foods, it is easier to discuss foods that, if consumed frequently, appear to increase risk for developing diabetes. I am not sure you are going to like the answer! Researchers Liese et al. evaluated dietary patterns that are associated with developing diabetes in a large cohort of people in the Insulin Resistance Atherosclerosis Study; in this study, the following foods were founds to increase risk for developing type 2 diabetes: red meat, low-fiber bread and cereal, dried beans, fried potatoes, tomato vegetables (maybe ketchup on fries), eggs, cheese and cottage cheese (7). People who consumed these foods commonly had up to a 4-fold risk of developing diabetes! The association with egg consumption was recently confirmed in a separate study; Djousse et al. reported that in both men and women, eating eggs 5-7 days per week increases risk of developing diabetes up to 77%! (8) Similarly, increased red meat consumption has been identified in multiple larger studies to clearly increase the risk of developing type 2 diabetes (9-12); this is thought to be due to its high concentration of iron, which may increase oxidative stress in the body.

Are there foods that are protective against developing type 2 diabetes? The good news is, yes, some dietary patterns appear to be protective against developing diabetes. Protective foods include: low glycemic index, whole grains, coffee, non-fried vegetables, fruit, and moderate wine consumption (9,13,14).

Measuring success in pre-diabetes treatment

Although you may hear differently from your own doctor, I measure success in treating pre-diabetes as a stabilization of fasting blood sugar, and a prevention of progressing to frank diabetes. Ideally, with weight loss and increases in physical activity there is also a reduction in fasting blood sugar back into the normal, non-pre-diabetes range, however reductions can take longer than stabilization.

I do not encourage daily, or even frequent, blood sugar testing at home for my patients with pre-diabetes because I have found that the variability in home glucometer measurements can make even the most systematic efforts end up frustrating for the person. Therefore, instead of frequent blood sugar monitoring, we follow-up more frequently on levels of physical activity, dietary changes that are in place or in development and on reducing stress; every 3-6 months we will do lab testing to be sure the blood glucose has stabilized or improved and then develop the next set of treatment strategies.

Because it has been shown that increased arterial plaque is present in people with pre-diabetes (15), addressing other risk factors for heart disease is also a critical element of reducing risk in people with pre-diabetes; blood pressure, cholesterol and triglycerides should also be treated to optimal levels with lifestyle, supplementation and medications as needed.


Although pre-diabetes does precede diabetes, it is an earlier step in the continuum of the disease process, not a disease-free state. Without weight loss and lifestyle change, pre-diabetes will progress and become type 2 diabetes, a leading cause of heart disease, blindness and kidney disease. Over time, even drug treatments to “prevent” diabetes will fail and more medications will be necessary to control the disease. Clinical research has definitively shown that type 2 diabetes can be prevented by lifestyle changes, including small reductions in weight (< 10% in most cases!). Physical activity to recommended levels (150 minutes per week) and making dietary choices now can prevent pre-diabetes from becoming type 2 diabetes. If you are an adult aged 35 or older, have had poly-cystic ovarian disease, gestational diabetes with pregnancy, and/or are a member of an “at-risk” ethnicity like Black Americans, Latino Americans or Asian Americans get properly screened for pre-diabetes by your doctor. Knowing your blood sugar status can help you make the changes necessary to prevent diabetes now!



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