Prediabetes means you have a higher than normal blood sugar level. It's not high enough to be considered type 2 diabetes yet, but without lifestyle changes, adults and children with prediabetes are more likely to develop 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, making physical activity part of your daily routine and staying at a healthy weight can help bring your blood sugar level back to normal. The same lifestyle changes that can help prevent type 2 diabetes in adults might also help bring children's blood sugar levels back to normal.

Prediabetes doesn't usually have any signs or symptoms.

One possible sign of prediabetes 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
• Excess hunger
• Fatigue
• 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 sugar screening if you have any risk factors for diabetes.

The exact cause of prediabetes is unknown. But family history and genetics appear to play an important role. A lack of regular physical activity and being overweight with excess fat around your abdomen 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 builds up in the blood instead of doing its normal job of giving energy to 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 called insulin.

Insulin comes from a gland located behind the stomach called the pancreas. Your pancreas sends insulin to your blood when you eat.

As insulin circulates, it allows sugar to enter your cells — and lowers the amount of sugar in your blood. When your blood sugar level starts to drop, the pancreas slows down the secretion of insulin into the blood.

When you have prediabetes, this process doesn't work as well. Your pancreas may not make enough insulin or cells become resistant to insulin and don't allow as much sugar in. So, instead of fueling your cells, sugar builds up in your bloodstream.

The same factors that increase the odds of getting type 2 diabetes also increase the risk of 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.
• Diet. 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 sugar for energy and makes the body use insulin more effectively.
• Age. Although diabetes can develop at any age, the risk of prediabetes increases after age 45.
• Family history. Your risk of prediabetes increases if you have a parent or sibling with type 2 diabetes.
• Race or ethnicity. Although it's unclear why, certain people — including Black, Hispanic, American Indian and Asian American people — are more likely to develop prediabetes.
• Gestational diabetes. If you had diabetes while pregnant (gestational diabetes), you and your child are at higher risk of developing prediabetes. If you've had gestational diabetes, your doctor will likely check your blood sugar levels at least once every three years.
• Polycystic ovary syndrome. Women with this common condition — characterized by irregular menstrual periods, excess hair growth and obesity — have a higher risk of prediabetes.
• Sleep. People with obstructive sleep apnea — a condition that disrupts sleep repeatedly — have an increased risk of insulin resistance.
• Tobacco smoke. Smoking may increase insulin resistance. Smokers also seem to carry more weight around the middle.

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
• Stroke
• Kidney disease
• Nerve damage
• Vision problems, possibly loss of vision
• Amputations

Prediabetes has been linked with unrecognized (silent) 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 at least 150 minutes of moderate aerobic physical activity a week, or about 30 minutes on most days of the week
• Lose excess weight
• Control your blood pressure and cholesterol
• Don't smoke

The American Diabetes Association (ADA) recommends that diabetes screening for most adults begin at age 45. The ADA advises diabetes screening before age 45 if you're 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 shows your average blood sugar level for the past three months. The test measures the percentage of blood sugar attached to the oxygen-carrying protein in red blood cells called hemoglobin. The higher your blood sugar levels, the more hemoglobin you'll have with sugar attached.

In general:

• An A1C level below 5.7% is considered normal
• An A1C level between 5.7% and 6.4% is considered prediabetes
• An A1C level of 6.5% or higher on two separate tests indicates type 2 diabetes

Certain conditions can make the A1C test inaccurate — such as if you're pregnant or have an uncommon form of hemoglobin.

Fasting blood sugar test

A blood sample is taken after you fast for at least eight hours or overnight.

In general:

• 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.

In general:

• 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, your doctor will typically check your blood sugar levels at least once a year.

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 one or more 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, Native American, Asian American and Pacific Islander are at higher risk.
• 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. Eat a variety of foods to help you achieve your goals without compromising taste or nutrition.
• Be more active. Aim for at least 150 minutes of moderate or 75 minutes of vigorous aerobic activity a week.
• Lose excess weight. If you're overweight, losing just 5% to 7% of your body weight — about 14 pounds (6.4 kilograms) if you weigh 200 pounds (91 kilograms) — can reduce the risk of type 2 diabetes. To keep your weight in a healthy range, focus on permanent changes to your eating and exercise habits.
• Stop smoking. Smoking may up your risk of developing type 2 diabetes.
• Take medications as needed. If you're at high risk of diabetes, your doctor might recommend metformin (Glumetza, 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
• Reducing portion sizes
• Eating out less often
• Spending at least one hour every day in physical activity

Medication generally isn't recommended for children with prediabetes unless lifestyle changes aren't improving blood sugar levels. If medication is needed, metformin (Glumetza, others) is usually the recommended drug.

Many alternative therapies have been touted as possible ways to treat or prevent type 2 diabetes. But, there's no definitive evidence that any alternative treatments are effective. Therapies that have been said to be helpful in type 2 diabetes and are also likely to be safe, include:

• Cassia cinnamon
• Flaxseed
• Ginseng
• Magnesium
• Oats
• Soy
• Xanthan gum

Talk to your doctor if you're considering dietary supplements or other alternative therapies to treat or prevent prediabetes. Some 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.

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), a dietitian or a certified diabetes educator.

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?
• Can you recommend any local programs for preventing diabetes?

What to expect from your doctor

Your doctor is likely to ask you a number of questions, such as:

• 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?