Overview

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.

Symptoms

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.

Causes

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.

Risk factors

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. 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 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.

Complications

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.

Prevention

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