What Is Prediabetes?

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Around 96 million American adults have prediabetes. Most—roughly 80%—aren't aware they have the condition.

Prediabetes does not typically cause symptoms. It is still a concern, however, because it is a precursor to type 2 diabetes. This means that without intervention, it can progress to type 2 diabetes, putting you at risk for a host of related complications.

This article discusses prediabetes, its symptoms, causes, and diagnosis. It also looks at how prediabetes is treated and what you can do to prevent it from progressing.

prediabetes symptoms

Verywell / Ellen Lindner

Prediabetes Symptoms

Prediabetes is also known as impaired glucose tolerance or impaired fasting glucose. It usually affects adults between the ages of 40 and 60.

The condition tends to be silent. It rarely causes noticeable symptoms. Most people who are diagnosed with prediabetes don't know exactly when it began. The condition can remain stable for years before progressing to diabetes.

In the rare cases when prediabetes does cause symptoms, they usually are subtle. This means they are easily missed or mistaken for other health issues.

Signs of prediabetes include:

  • Excessive hunger or thirst
  • Weight gain
  • Fatigue
  • Polyuria (frequent urination)

Complications

Without treatment, prediabetes can progress to type 2 diabetes. Type 2 diabetes is a medical condition that causes a number of health complications, including:

Prediabetes is not associated with type 1 diabetes, a form that usually appears in childhood. It is also not related to diabetes insipidus, a condition that affects the kidneys.

Causes

Insulin is a hormone produced by the pancreas. It helps the cells in the body store glucose, an important source of energy. This keeps blood sugar levels within a healthy range.

If you have prediabetes, you probably make enough insulin. Your body's cells, however, are resistant to insulin and its effects. This results in decreased energy and a slightly elevated blood glucose level.

Risk Factors

The exact cause of prediabetes is not known. There are several known risk factors, however. For example, people who don't get much exercise may be at risk of prediabetes. Other risk factors include:

It is not clear whether these health problems cause or are caused by prediabetes. It is also possible they are all caused by another factor.

Associated Conditions

Several changes in your body can take place before you develop prediabetes.

Insulin resistance begins before prediabetes. It might not cause high blood sugar.

A similar condition called metabolic syndrome can also develop before or alongside prediabetes. It is characterized by:

  • Excess weight
  • Hypertension
  • High cholesterol
  • Insulin resistance

Diagnosis

Prediabetes is diagnosed with the same blood tests used to diagnose type 2 diabetes.

Because prediabetes typically does not cause symptoms, it usually is detected during routine screening for diabetes. The American Diabetes Association (ADA) recommends screening at age 35 and testing again every three years if the results are normal.

The ADA also advises testing for adults of any age who have a high body mass index (BMI) and one or more risk factors for diabetes. For most people, a BMI of 25 kg/m2 or greater is considered high. For people of Asian ancestry, a high BMI is 23 kg/m2 or higher.

BMI is a flawed measure that does not take into account factors such as body composition, ethnicity, sex, race, and age. Still, BMI is widely used in the medical community because it’s an inexpensive and quick way to analyze a person’s potential health status and outcomes.

Risk factors for diabetes include:

  • Belonging to a high-risk race or ethnic population, specifically, people of African ancestry, Latinos, Native Americans, people of Asian ancestry, and Pacific Islanders
  • Having a parent or sibling with a history of diabetes
  • Having a history of cardiovascular disease
  • Having hypertension (blood pressure is 140/90 mmHg or higher) or taking medication to treat it
  • Having low levels of HDL (good) cholesterol or high levels of triglycerides
  • Being physically inactive
  • Having conditions associated with insulin resistance, including acanthosis nigricans, severe obesity, or polycystic ovary syndrome

Additionally, testing should be performed for those who:

Screening Tests

With prediabetes, blood glucose is often only mildly elevated. This means it may take more than one type of blood test to diagnose the condition.

The tests used to screen for prediabetes include:

  • Fasting blood sugar test: This test measures your blood sugar after you have gone without food for eight hours. Normal fasting glucose is below 100 mg/dL. Anything in the 100 to 125 mg/dL range suggests prediabetes; a level of 126 mg/dL or above suggests diabetes.
  • Glucose tolerance test: This test measures your blood glucose level before and after you drink a carbohydrate drink. A normal glucose level after drinking a 75-gram glucose load is less than 140 mg/dL. A 140 to 199 mg/dL result indicates prediabetes, and 200 mg/dL or more indicates diabetes.
  • A1C test: Glucose sticks to hemoglobin A, a protein found in red blood cells. This is called glycation. When this happens, the glucose remains stuck there for the life of the protein, or around 120 days. The A1C test measures what percentage of hemoglobin A proteins are glycated. For example, an A1C of 7% means that 7% of hemoglobin A proteins are glycated. This tells you your average blood sugar levels for the previous two to three months. Prediabetes is diagnosed when an A1C test is in the range of 5.7 % to 6.4 %. Anything under 5.7 % is considered normal. An A1C of 6.5 % or higher is considered diabetes.

Glucose Monitoring

Glucose monitoring isn't required for prediabetes. Still, if you have prediabetes you may choose to monitor glucose at home. This can help you keep track of how well your treatment plan is working.

There are many easy-to-use glucose monitors. These include options that continuously monitor glucose levels.

Treatment

There are well-established strategies for treating prediabetes and preventing type 2 diabetes.

Lifestyle modifications are usually the first approach. If you are overweight, losing even 5% to 10% of your body weight and getting regular exercise can help to prevent or delay type 2 diabetes.

It's important to be consistent in making these changes. Regular medical appointments and glucose monitoring can help keep you on track.

Other things you can do to manage prediabetes include:

  • Reducing your carbohydrate intake: Carbs impact blood sugar more than other macronutrients. It's especially important to avoid refined carbs, such as white bread, pasta, rice, and snack foods. You should also eliminate juice and other sweetened beverages and increase your intake of non-starchy vegetables.
  • Following a Mediterranean diet: This means focusing on fruits, vegetables, and healthy fats like nuts, seeds, and olive oil.
  • Being more active: Exercise helps keep weight in check and helps the body better use insulin. Physical activity can help cut your risk for diabetes by 30 to 50%.

If lifestyle changes aren't effective, a healthcare provider might recommend medication like Glucophage (metformin). This drug has been shown to help prevent the development of type 2 diabetes.

Summary

Prediabetes is when your blood sugar is high, but not as high as when you have diabetes. If unmanaged, it can develop into type 2 diabetes.

Prediabetes usually has no symptoms. You may be at risk for developing prediabetes if you have high blood pressure, high cholesterol, or excess body fat.

Prediabetes is diagnosed with blood tests. People over the age of 35 should test every three years. Those who have risk factors should test more often. 

​A Word From Verywell

It is important to be screened if you have any risk factors for diabetes. If your tests show signs of prediabetes, simple lifestyle changes are often enough to prevent diabetes. Losing weight, exercising, and adopting a diet low in sugar and unhealthy fats and rich in nutrients will also improve your overall health and well-being.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Barbie Cervoni MS, RD, CDCES, CDN
Barbie Cervoni MS, RD, CDCES, CDN, is a registered dietitian and certified diabetes care and education specialist.