A person with borderline diabetes, also known as prediabetes, has blood sugar levels that are higher than they should be but not yet high enough for a diagnosis of type 2 diabetes.

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Prediabetes is a condition that can progress to type 2 diabetes.

Research shows that this progression occurs in about 25% of people with prediabetes within 3–5 years. Overall, up to 70% of people with prediabetes will develop diabetes at some point in their life.

Doctors may also refer to borderline diabetes as impaired glucose tolerance or impaired fasting glucose.

This article looks at how to recognize risk factors for prediabetes, manage the condition, and prevent type 2 diabetes from developing.

Borderline diabetes does not have clear symptoms. Some people may not be aware that they have it until:

If a person’s blood sugar level remains high, they may begin to develop some symptoms of type 2 diabetes. These include frequent urination and increased thirst.

However, most people will not know they have prediabetes until they receive testing.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a range of other conditions and factors can increase the risk of prediabetes, including:

People with a family history of type 2 diabetes may also have an increased risk, suggesting that genetics play a role.

According to the American Heart Association (AHA), the following lifestyle factors may also be a risk for prediabetes in some people:

  • raised stress levels
  • smoking
  • drinking too much alcohol

Regularly consuming high sugar drinks may also increase the risk. A 2017 review found that people who regularly drink sugary beverages face an increased risk of metabolic diseases, such as high blood pressure and high levels of blood glucose and triglycerides. These metabolic conditions can lead to prediabetes and diabetes.

People who lead an inactive lifestyle also have a higher risk of taking in too many calories without burning them through exercise.

Other people who may be at risk of developing prediabetes include those who have polycystic ovary syndrome (PCOS) or have experienced instances of high blood sugar levels in the past.

Anyone with any of these risk factors may benefit from a prediabetes screening to check whether they have the condition.

A doctor typically uses blood tests to diagnose prediabetes. A glucose tolerance test is particularly useful because it measures how quickly the body can process the sugar in the blood in a 2-hour period.

Other options include a fasting blood test, which measures blood sugar levels after a person has not eaten for a specific period, and an A1C test, which measures the average blood sugar levels over 2–3 months. People do not need to fast or take any special liquids or medications for the A1C test, and it gives reliable results.

The American Diabetes Association states that a doctor will diagnose prediabetes when test results show the following measurements:

  • fasting blood sugar levels of 100–125 milligrams per deciliter (mg/dl)
  • glucose tolerance levels of 140–199 mg/dl
  • an A1C test result of 5.7–6.4%

A doctor will often re-test these levels to confirm that the readings are not due to one-off spikes in blood sugar.

Who should undergo screening for prediabetes?

The NIDDK recommends that people with the following risk factors undergo a prediabetes screening:

  • an age of 45 years or over
  • a body mass index (BMI) of 25 or higher
  • a waist circumference larger than 40 inches in males or 35 inches in females
  • a close relative with diabetes
  • a condition that increases insulin resistance, including PCOS, acanthosis nigricans, and non-alcohol-related steatohepatitis
  • certain racial or ethnic backgrounds, including African American, Asian American, Hispanic, Latino, Native American, Alaska Native, and Pacific Islander
  • a history of gestational diabetes, which is diabetes during pregnancy
  • having given birth to an infant weighing more than 9 pounds
  • having a disease that hardens the arteries
  • recent treatment with glucocorticoids or atypical antipsychotic medications

If a doctor identifies any of these risk factors, they may recommend that the person has a screening to check their blood glucose levels.

Medical professionals advise repeating screening tests every 1–3 years for people with these risk factors.

The NIDDK has an official resource that people can use to check their diabetes risk.

However, anyone who is concerned that they may have borderline diabetes should visit a doctor for testing and a diagnosis.

Prediabetes is reversible, but it is often easier to prevent than treat. Lifestyle factors are the primary cause of prediabetes, and making changes in some aspects of life can significantly reduce the risk.

Diet

Alongside regular exercise, a balanced, nutritious diet that moderates sugar intake can help reverse borderline diabetes.

According to the American Diabetes Association, many people can improve their diet by:

  • increasing the intake of unprocessed high fiber carbohydrates
  • increasing fruit and vegetable consumption
  • reducing the intake of saturated fats and processed meat

Learn more about what to eat with prediabetes.

Physical activity

Exercise is also important. Research shows that regular physical activity may help slow the progression of prediabetes to diabetes.

The current Physical Activity Guidelines for Americans recommend that adults do at least 150–300 minutes of moderate-intensity aerobic activity each week. In addition, they should perform muscle-strengthening exercises, such as lifting weights or doing pushups, at least twice a week.

Examples of moderate-intensity exercise are fast dancing and brisk walking.

Regular exercise and a nutritious diet not only help reduce the risk of developing diabetes but also protect the heart against future diseases.

Combining nutrition and exercise

In addition, there is strong evidence for the benefits of combining exercise and dietary interventions in reducing diabetes risk and reversing prediabetes.

This primarily comes from the Diabetes Prevention Program (DPP), which was a long-term study aiming to identify practical steps to prevent diabetes. The people who took part in the DPP Lifestyle Change Program aimed to lose 7% of their body weight and maintain this loss through dietary changes and physical activity.

All of the participants in the program received advice on how to diet and exercise, and they attended lifestyle change classes for the duration of the study.

After 3 years, in comparison with those who took a placebo, people in the program had a 58% drop in the risk of developing type 2 diabetes regardless of sex or ethnicity. Among those aged 60 years and older, the decrease in risk was 71%.

The researchers held regular follow-up sessions. After 15 years, people in the DPP Lifestyle Change Program continued to see a delay in the onset of diabetes compared with people who took a medication called metformin or a placebo.

Anyone who developed diabetes during the study received extra medical care. However, diet and exercise remained important in managing the symptoms and reducing the risk of complications.

Regular monitoring

Managing prediabetes also involves continual monitoring of the risk factors and regular testing of blood sugar levels.

In addition to lifestyle changes, doctors may recommend other ways to minimize the risk of developing diabetes. Medical management may include treating related conditions, such as obesity and heart disease.

Prediabetes is the stage before type 2 diabetes develops. By this stage, blood sugar and insulin resistance may start reaching harmful levels.

Prediabetes does not usually cause active symptoms, and most people will not be aware that they have the condition until it progresses to diabetes and starts causing severe health problems.

Therefore, it is advisable for anyone who is at risk of developing diabetes to undergo regular screening. Risk factors include high BMI and waist circumference, an age of 45 years or older, and the presence of other cardiovascular diseases.

Prediabetes is often reversible with a sustained exercise program and a balanced, low sugar diet.

Below, we answer some commonly asked questions about prediabetes.

Which foods should I eat if I have prediabetes?

Fat and fiber tend to slow absorption and lower what is called the glycemic index (GI) of foods. Low GI fruits and vegetables, such as stone-ground whole wheat bread, rolled or steel-cut oatmeal, nonstarchy vegetables, and whole fruits are good choices. Experts consider a low GI food to have a rating of 55 or less. A person can use this database to find the GI of common foods.

What are the complications of prediabetes?

Even if it does not progress to type 2 diabetes, prediabetes can lead to long-term cardiovascular and kidney damage.

Can children have prediabetes?

In a 2019 study involving 5,786 people, 18% of the 2,606 adolescents — those aged 12–18 years — had prediabetes. Among the 3,180 young adults, the prevalence was 24%.

Many children who develop type 2 diabetes do not receive a diagnosis until adolescence. This is, in part, because puberty hormones can make it harder for the body to regulate insulin. Parents and caregivers can help prevent diabetes in children by encouraging them to eat a balanced diet and engage in plenty of physical activity.

Can prediabetes progress to type 1 diabetes?

Prediabetes refers to a metabolic state that is a precursor to type 2 diabetes. It cannot evolve into type 1 diabetes. However, there is research on a parallel disease called pre-type 1 diabetes, in which a person’s immune system displays certain characteristics that indicate progression to type 1 diabetes.

Learn about the differences between type 1 diabetes and type 2 diabetes.

How long does it take to reverse prediabetes?

With a well-balanced diet, regular exercise, and prescribed medical interventions, a person may be able to reverse prediabetes in about 3 years.