Also called: Chemical Diabetes, Borderline Diabetes, Impaired Fasting Glucose, Subclinical Diabetes, Impaired Glucose Tolerance, IFG, Latent Diabetes, IGT


A patient is diagnosed as having prediabetes when glucose (blood sugar) is higher than normal but not high enough to be diagnosed as diabetes. At least 43 million Americans have this condition, according to estimates by the government. Prediabetes is almost always present in an individual before type 2 diabetes develops.

Screening for prediabetes is an effective strategy for identifying individuals who are at risk for developing type 2 diabetes. By identifying the individuals with prediabetes, physicians can intervene sooner with a plan of treatment. Changes in lifestyle, such as diet, weight loss and exercise, are usually included in the treatment. These interventions have been successful in delaying or preventing type 2 diabetes.

Detection and treatment of prediabetes also may reduce the risk of heart disease, stroke and other complications. The damage that occurs to organs and body systems from type 2 diabetes, such as diabetic neuropathy and diabetic retinopathy, can actually start during prediabetes. Treatment of prediabetes promotes a healthier lifestyle, which in turn can prevent type 2 diabetes and medical complications.

About prediabetes

Prediabetes exists when a person has glucose (blood sugar) levels higher than normal but not high enough to be diagnosed as diabetes. It often, but not always, escalates to type 2 diabetes, which accounts for an estimated 90 to 95 percent of cases of diabetes.

In the past, mildly elevated levels of glucose were often ignored. Today, glucose levels slightly above the normal range are a warning sign for an individual to take prompt action to prevent type 2 diabetes. In addition to being a strong risk factor for diabetes, prediabetes increases a person’s risk for heart disease and stroke, the U.S. Centers for Disease Control and Prevention (CDC) warns.

In the United States and worldwide, there has been a steady increase in the number of people diagnosed with diabetes. According to the CDC, the number of new cases of Americans diagnosed with diabetes increased by 54 percent between 1997 and 2004.

The CDC estimated in 2005 that, based on statistics from 1988 to 1994, 41 million Americans ages 40 to 74 had prediabetes – 40 percent of the total population in that age bracket. About 2 million American adolescents have prediabetes, according to a 2006 federal study using data from a 1999-2000 national survey. The CDC did not have more current statistics available as of early 2007, but with rates of obesity soaring in recent years, the number of people with prediabetes is now likely higher.

Given these facts, scientists are researching ways to identify people at risk for diabetes earlier. Unlike type 1 diabetes, it is believed that that with early identification, type 2 diabetes may be delayed or even prevented. A diagnosis of prediabetes has emerged as a condition for predicting individuals at risk for type 2 diabetes.

Prediabetes can be diagnosed by a physician using standard glucose tests. A fasting blood glucose test (FPG) or an oral glucose tolerance test (OGTT) can be used to identify the condition. These tests measure the level of glucose in the blood. If the level of glucose is found to be within a certain elevated range, prediabetes is diagnosed. The range, in milliliters per deciliter of blood, is 100 to 125 mg/dL for a fasting blood glucose test and 140 to 199 mg/dL for an oral glucose challenge test.

Even glucose at the high range of normal may be a concern. A recently completed 12-year Israeli study of more than 13,000 troops found that those with fasting glucose of 95 to 99 mg/dL were several times more likely than those with lower glucose to become diabetic.

Studies conducted by the U.S. Department of Health and Human Services indicate that individuals with prediabetes will likely develop type 2 diabetes within 10 years unless changes are made to their lifestyle. In addition, women diagnosed with prediabetes are at a high risk of developing gestational diabetes during pregnancy.

Treating prediabetes helps prevent the onset to type 2 diabetes and is important for other reasons as well. Research has shown that medical complications linked to diabetes may actually start in the prediabetes stage. The heart, blood vessels, kidneys and eyes may be damaged during the prediabetes stage. Treatment and prevention in the prediabetic state may slow down the damage of vital organs and body systems.

Recent research shows that:

  • Almost 8 percent of the (prediabetic) participants in the Diabetes Prevention Program developed early-stage diabetic retinopathy.
  • People with prediabetes are more likely to develop chronic kidney disease than those with normal glucose, mainly because of cardiovascular risk factors such as high blood pressure.

  • Prediabetes increases the risk of heart disease, according to a nine-year study of more than 28,000 patients.

  • The type of nerve damage associated with diabetes (diabetic neuropathy) can be present in people with prediabetes.

  • Prediabetic women have increased risk of urinary incontinence, which can be improved with weight loss.

A condition related to prediabetes that also often develops before type 2 diabetes is insulin resistance, an impairment in the body’s ability to use insulin to process glucose for energy. In addition, people with prediabetes may have a cluster of cardiovascular risk factors known as metabolic syndrome.

Potential causes of prediabetes

As with type 2 diabetes, there is no single cause for prediabetes. The same risk factors for type 2 diabetes are present for prediabetes. People are at higher risk for prediabetes if they have one or more of the following risk factors:

  • Age over 45
  • Family history of diabetes
  • Overweight or obesity
  • High blood pressure
  • Low HDL (good) and high LDL (bad)cholesterol, and elevated triglycerides
  • Belonging to certain racial and ethnic groups (American Indian, black, Latino, Asian, Pacific Islander) 
  • History of gestational diabetes or having given birth to a  baby heavier than 9 pounds (macrosomia)
  • History of  polycystic ovarian syndrome (PCOS)

Other conditions that may increase risk of prediabetes include fatty liver disease and male hypogonadism (low levels of testosterone).

Symptoms and diagnosis

Prediabetes usually has no symptoms. In some instances a patient may experience symptoms of type 2 diabetes such as increased thirst (polydipsia), frequent urination (polyuria), increased hunger (polyphagia), fatigue, blurred vision, frequent infections, slow-healing wounds or other diabetic symptoms. 

In uncommon cases, some patients have experienced symptoms of diabetic neuropathy, such as tingling, numbness, pain or itching in the legs or elsewhere.

To screen for prediabetes and diabetes, the American Diabetes Association recommends that anyone 45 years or older have a glucose test.Glucose screening is particularly important if the individual is overweight, obese or has a family history of diabetes.

In addition, overweight individuals under the age of 45 may be screened if they have any of the other risk factors for diabetes. Children and adolescents who are at risk should be screened every 2 years after the age of 10, or at the onset of puberty if it occurs at a younger age.

There are two standard tests used for diagnosing prediabetes. They are administered differently but both provide results that indicate high glucose (blood sugar) levels and prediabetes.

These tests, which can be administered in a physician’s office, are:

  • Fasting plasma glucose test(FPG).  A sample of blood is taken from the vein after an individual has not had anything to eat or drink for eight to 10 hours. The blood is tested for the amount of glucose that is present in the sample. Fasting glucose that is between 100 and 125 milligrams per deciliter (mg/dL) indicates prediabetes.
  • Oral glucose tolerance test (OGTT). This test requires an individual to drink 8 ounces of a glucose solution after fasting overnight. The glucose is measured before drinking the liquid, then every hour for a two– to three–hour period. Glucose levels that rise to between 140 and 199 mg/dL indicate prediabetes.

Glucose Levels for Prediabetes and Diabetesin milligrams per deciliter

99 or lower100 to 125126 or higher
139 or lower140 to 199200 or higher

Both tests should be performed at different times to confirm a diagnosis of prediabetes. Once diagnosed with prediabetes, the person will be given a plan of treatment by the physician to help prevent type 2 diabetes.

Treatment and prevention for prediabetes

A panel of physicians and diabetes experts from the Centers for Disease Control and Prevention (CDC) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) concluded that treatment for prediabetes is crucial for several reasons. These reasons include:

  • Damage to vital organs and systems in the body from high glucose (blood sugar) levels can begin in the prediabetes stage.
  • Having glucose levels in the prediabetic range places a person at a 50 percent higher risk for having a heart attack or stroke.
  • With modest lifestyle changes, the development of type 2 diabetes can be delayed or prevented.
  • Lifestyle changes can return elevated glucose levels to the normal range.

The U.S. Department of Health and Human Services (HHS) conducted a large prevention study of prediabetic people at high risk for diabetes. In the Diabetes Prevention Program, lifestyle changes reduced the development of type 2 diabetes by 58 percent over three years. Based on this study, HHS recommended the following changes in lifestyle:

  • Weight loss. Modest weight loss in overweight individuals has been shown to prevent or delay type 2 diabetes. The recommended goal is 5 to 10 percent of the person’s body weight. Reduced weight may also decrease other risks such as high blood pressure and unhealthy levels of cholesterol.
  • Physical activity. Even modest exercise or other physical activity decreases the risk of getting type 2 diabetes. Sedentary lifestyles do not help prediabetic patients. Modest physical activity of 30 minutes per day is recommended for reducing risk. It can be activity as simple as walking and can be split into several sessions per day. The total amount of exercise recommended is a minimum of 150 minutes per week.

Exercise improves cardiovascular function and circulation and can improve blood pressure and cholesterol levels. Recent research indicates that regular exercise may even stop prediabetic neuropathy.

The Diabetes Prevention Program also examined antidiabetic agents including metformin, a biguanide, were also examined in the Diabetes Prevention Program. These drugs sensitize the body to the actions of insulin. The chance of preventing type 2 diabetes with medication varied according to the age and weight of the individual and the type of medication. Metformin reduced the risk of developing type 2 diabetes by 31 percent over a three–year period. The study concluded that drug therapy, though effective, appeared to be less beneficial than the 58 percent reduction through lifestyle changes for the prevention of type 2 diabetes.

Making improvements in weight and physical activity is the best way to prevent prediabetes from progressing to type 2 diabetes. Other lifestyle changes that may be included in a treatment plan for prediabetes are:

  • Eat a good diet that is low in fats and sweets, and high in fiber
  • Stop smoking
  • Avoid excessive use of alcohol
  • Treat high blood pressure and unhealthy cholesterol levels

Modest consumption of alcohol can decrease an individual’s risk of diabetes, according to the Harvard School of Public Health, but heavier consumption is harmful.

As with type 2 diabetes, a physician must recommend any changes and prescribe a plan of treatment specific to the patient. Once the plan is in place, it is important the individual closely follow the treatment to maximize the chances for a healthy life without diabetes.

Questions for your doctor on prediabetes

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about prediabetes:

  1. Do I have, or am at risk of developing, prediabetes?
  2. What diagnostic tests should I have, and what do they involve?
  3. How often should I have a glucose test to screen for prediabetes?
  4. What do my test results show?
  5. Should I be concerned if my blood sugar is at the high range of normal but not yet prediabetic?
  6. Are there any signs or symptoms of prediabetes I should watch for?
  7. How can exercise help me avoid prediabetes or diabetes?
  8. What types of exercise should I do? How much and how often?
  9. How can I improve my diet to help avoid prediabetes or diabetes?
  10. How much weight do I need to lose, and at what pace?
  11. Can/should my prediabetes be treated with diabetes medication?
  12. Will treating my obesity, high blood pressure, unhealthy cholesterol levels or other risk factors help me fight prediabetes? Can quitting smoking also reduce my risk?
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