Medically reviewed on Aug 2, 2017
Prediabetes means that your blood sugar level is higher than normal but not yet high enough to be type 2 diabetes. Without lifestyle changes, people with prediabetes are very likely to progress to type 2 diabetes. If you have prediabetes, the long-term damage of diabetes — especially to your heart, blood vessels and kidneys — may already be starting.
There's good news, however. Progression from prediabetes to type 2 diabetes isn't inevitable. Eating healthy foods, incorporating physical activity in your daily routine and maintaining a healthy weight can help bring your blood sugar level back to normal.
Prediabetes affects adults and children. The same lifestyle changes that can help prevent progression to diabetes in adults might also help bring children's blood sugar levels back to normal.
Prediabetes generally has no signs or symptoms.
One possible sign that you may be at risk of type 2 diabetes is darkened skin on certain parts of the body. Affected areas can include the neck, armpits, elbows, knees and knuckles.
Classic signs and symptoms that suggest you've moved from prediabetes to type 2 diabetes include:
- Increased thirst
- Frequent urination
- Blurred vision
When to see a doctor
See your doctor if you're concerned about diabetes or if you notice any type 2 diabetes signs or symptoms. Ask your doctor about blood glucose screening if you have any risk factors for prediabetes.
The exact cause of prediabetes is unknown. But family history and genetics appear to play an important role. Inactivity and excess fat — especially abdominal fat — also seem to be important factors.
What is clear is that people with prediabetes don't process sugar (glucose) properly anymore. As a result, sugar accumulates in the bloodstream instead of doing its normal job of fueling the cells that make up muscles and other tissues.
Most of the glucose in your body comes from the food you eat. When food is digested, sugar enters your bloodstream. Moving sugar from your bloodstream to your body's cells requires a hormone (insulin).
Insulin comes from a gland located behind the stomach (pancreas). Your pancreas secretes insulin into your bloodstream when you eat.
As insulin circulates, it allows sugar to enter your cells — and lowers the amount of sugar in your bloodstream. As your blood sugar level drops, so does the secretion of insulin from your pancreas.
When you have prediabetes, this process begins to work improperly. Instead of fueling your cells, sugar builds up in your bloodstream. High blood sugar occurs when your pancreas doesn't make enough insulin or your cells become resistant to the action of insulin, or both.
The same factors that increase the risk of developing type 2 diabetes increase the risk of developing prediabetes. These factors include:
- Weight. Being overweight is a primary risk factor for prediabetes. The more fatty tissue you have — especially inside and between the muscle and skin around your abdomen — the more resistant your cells become to insulin.
- Waist size. A large waist size can indicate insulin resistance. The risk of insulin resistance goes up for men with waists larger than 40 inches and for women with waists larger than 35 inches.
- Dietary patterns. Eating red meat and processed meat, and drinking sugar-sweetened beverages, is associated with a higher risk of prediabetes. A diet high in fruits, vegetables, nuts, whole grains and olive oil is associated with a lower risk of prediabetes.
- Inactivity. The less active you are, the greater your risk of prediabetes. Physical activity helps you control your weight, uses up glucose as energy and makes your cells more sensitive to insulin.
- Age. Although diabetes can develop at any age, the risk of prediabetes increases after age 45. This may be because people tend to exercise less, lose muscle mass and gain weight as they age.
- Family history. Your risk of prediabetes increases if you have a parent or sibling with type 2 diabetes.
- Race. Although it's unclear why, people of certain races — including African-Americans, Hispanics, Native Americans, Asian-Americans and Pacific Islanders — are more likely to develop prediabetes.
- Gestational diabetes. If you developed gestational diabetes while pregnant, you and your child are at higher risk of developing prediabetes. If you gave birth to a baby who weighed more than 9 pounds (4.1 kilograms), you're also at increased risk of prediabetes.
- Polycystic ovary syndrome. This common condition — characterized by irregular menstrual periods, excess hair growth and obesity — increases women's risk of prediabetes.
- Sleep. People with a certain sleep disorder (obstructive sleep apnea) have an increased risk of insulin resistance. People who work changing shifts or night shifts, possibly causing sleep problems, also may have an increased risk of prediabetes or type 2 diabetes.
Other conditions associated with prediabetes include:
- High blood pressure
- Low levels of high-density lipoprotein (HDL) cholesterol, the "good" cholesterol
- High levels of triglycerides — a type of fat in your blood
When these conditions occur with obesity, they are associated with insulin resistance. The combination of three or more of these conditions is often called metabolic syndrome.
The most serious consequence of prediabetes is progression to type 2 diabetes. That's because type 2 diabetes can lead to:
- High blood pressure
- High cholesterol
- Heart disease
- Kidney disease
Research indicates that prediabetes is often associated with unrecognized heart attacks and can damage your kidneys, even if you haven't progressed to type 2 diabetes.
Healthy lifestyle choices can help you prevent prediabetes and its progression to type 2 diabetes — even if diabetes runs in your family. Try to:
- Eat healthy foods
- Get more physical activity
- Lose excess pounds
- Control your blood pressure and cholesterol
The American Diabetes Association (ADA) recommends that blood glucose screening for adults begin at age 45, or sooner if you are overweight and have additional risk factors for prediabetes or type 2 diabetes.
There are several blood tests for prediabetes.
Glycated hemoglobin (A1C) test
This test indicates your average blood sugar level for the past two to three months. Specifically, the test measures the percentage of blood sugar attached to the oxygen-carrying protein in red blood cells (hemoglobin). The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached.
- An A1C level below 5.7 percent is considered normal
- An A1C level between 5.7 and 6.4 percent is considered prediabetes
- An A1C level of 6.5 percent or higher on two separate tests indicates type 2 diabetes
Certain conditions can make the A1C test inaccurate — such as if you are pregnant or have an uncommon form of hemoglobin (hemoglobin variant).
Fasting blood sugar test
A blood sample is taken after you fast for at least eight hours or overnight.
- A fasting blood sugar level below 100 milligrams per deciliter (mg/dL) — 5.6 millimoles per liter (mmol/L) — is considered normal.
- A fasting blood sugar level from 100 to 125 mg/dL (5.6 to 7.0 mmol/L) is considered prediabetes. This result is sometimes called impaired fasting glucose.
- A fasting blood sugar level of 126 mg/dL (7.0 mmol/L) or higher indicates type 2 diabetes.
Oral glucose tolerance test
This test is usually used to diagnose diabetes only during pregnancy. A blood sample is taken after you fast for at least eight hours or overnight. Then you'll drink a sugary solution, and your blood sugar level will be measured again after two hours.
- A blood sugar level less than 140 mg/dL (7.8 mmol/L) is considered normal.
- A blood sugar level from 140 to 199 mg/dL (7.8 to 11.0 mmol/L) is considered prediabetes. This is sometimes referred to as impaired glucose tolerance.
- A blood sugar level of 200 mg/dL (11.1 mmol/L) or higher indicates type 2 diabetes.
If you have prediabetes, further testing may be needed. At least once a year, your doctor will likely check your:
- Fasting blood sugar
- Hemoglobin A1C
- Total cholesterol, HDL, low-density lipoprotein (LDL), and triglycerides
Testing might occur more frequently if you have additional risk factors for diabetes.
Children and prediabetes testing
Type 2 diabetes is becoming more common in children and adolescents, likely due to the rise in childhood obesity. The ADA recommends prediabetes testing for children who are overweight or obese and who have at least two other risk factors for type 2 diabetes.
These other risk factors include:
- Family history of type 2 diabetes.
- Race. Children who are African-American, Hispanic or Native American are at higher risk.
- Sex and age. Type 2 diabetes is more common among girls than boys. A diagnosis of childhood type 2 diabetes often occurs during puberty — as early as age 10.
- Low birth weight.
- Being born to a mother who had gestational diabetes.
The ranges of blood sugar level considered normal, prediabetic and diabetic are the same for children and adults.
Children who have prediabetes should be tested annually for type 2 diabetes — or more often if the child experiences a change in weight or develops signs or symptoms of diabetes, such as increased thirst, increased urination, fatigue or blurred vision.
Healthy lifestyle choices can help you bring your blood sugar level back to normal, or at least keep it from rising toward the levels seen in type 2 diabetes.
To prevent prediabetes from progressing to type 2 diabetes, try to:
- Eat healthy foods. Choose foods low in fat and calories and high in fiber. Focus on fruits, vegetables and whole grains. Strive for variety to help you achieve your goals without compromising taste or nutrition.
- Be more active. Aim for 30 to 60 minutes of moderate physical activity most days of the week.
- Lose excess weight. If you're overweight, losing just 5 to 10 percent of your body weight — only 10 to 20 pounds (4.5 to 9 kilograms) if you weigh 200 pounds (91 kilograms) — can reduce the risk of developing type 2 diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits. Motivate yourself by remembering the benefits of losing weight, such as a healthier heart, more energy and improved self-esteem.
- Stop smoking.
- Take medications as needed. If you're at high risk of diabetes, your doctor might recommend metformin (Glucophage, others). Medications to control cholesterol and high blood pressure might also be prescribed.
Children and prediabetes treatment
Children with prediabetes should undertake the lifestyle changes recommended for adults with type 2 diabetes, including:
- Losing weight
- Eating fewer refined carbohydrates and fats, and more fiber
- Spending at least one hour every day in physical activity
Medication generally isn't recommended for children with prediabetes.
Many alternative therapies have been touted as possible ways to treat or prevent type 2 diabetes, including:
- Cassia cinnamon
- White mulberry
Although some of these substances have shown promise in early trials, there's no definitive evidence that any of these alternative therapies are effective.
Talk to your doctor if you're considering dietary supplements or other alternative therapies to treat or prevent prediabetes. Some of these supplements or alternative therapies might be harmful if combined with certain prescription medications. Your doctor can help you weigh the pros and cons of specific alternative therapies.
Preparing for an appointment
You're likely to start by seeing your primary care doctor. He or she may refer you to a doctor who specializes in diabetes treatment (endocrinologist).
Here's some information to help you get ready for your appointment.
What you can do
Before your appointment, take these steps:
- Ask about any pre-appointment restrictions. You'll probably need to fast for at least eight hours before your appointment so that your doctor can measure your fasting blood sugar level.
- List symptoms you've been having and for how long.
- List all medications, vitamins and supplements you take, including the doses.
- List key personal and medical information, including other conditions, recent life changes and stressors.
- Prepare questions to ask your doctor.
For prediabetes, some basic questions to ask your doctor include:
- How can I prevent prediabetes from turning into type 2 diabetes?
- Do I need to take medication? If so, what side effects can I expect?
- I have other health conditions. How can I best manage them together?
- How much do I need to exercise each week?
- Should I avoid any foods? Can I still eat sugar?
- Do I need to see a dietitian?
What to expect from your doctor
Examples of questions your doctor may ask, include:
- Has your weight changed recently?
- Do you exercise regularly? If so, for how long and how often?
- Do you have a family history of diabetes?