Often, prediabetes 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. This condition is called acanthosis nigricans. Common areas that may be affected include the neck, armpits, elbows, knees and knuckles.
Classic red flags that suggest you've moved from prediabetes to type 2 diabetes include:
- Increased thirst
- Frequent urination
- Blurred vision
When to see a doctor
Consult your doctor if you're concerned about diabetes or if you notice any type 2 diabetes signs or symptoms — increased thirst and frequent urination, fatigue, and blurred vision.
Ask your doctor about blood glucose screening if you have any risk factors for prediabetes, such as:
- You're overweight, with a body mass index above 25
- You're inactive
- You're age 45 or older
- You have a family history of type 2 diabetes
- You're African-American, Hispanic, American Indian, Asian-American or a Pacific Islander
- You developed gestational diabetes when you were pregnant or gave birth to a baby who weighed more than 9 pounds (4.1 kilograms)
- You have polycystic ovary syndrome — a condition characterized by irregular menstrual periods, excess hair growth and obesity
- You have high blood pressure
- Your high-density lipoprotein (HDL) cholesterol is below 35 milligrams per deciliter (mg/dL) (0.9 millimoles per liter, or mmol/L) or your triglyceride level is above 250 mg/dL (2.83 mmol/L)
The exact cause of prediabetes is unknown, although family history and genetics appear to play an important role. Researchers have discovered some genes that are related to insulin resistance. Excess fat — especially abdominal fat — and inactivity also seem to be important factors in the development of prediabetes.
What is clear is that people who have prediabetes aren't quite processing sugar (glucose) properly anymore. This causes sugar to build up 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 foods you eat, specifically foods that contain carbohydrates. Any food that contains carbohydrates can affect your blood sugar levels, not just sweet foods.
During digestion, sugar enters your bloodstream, and with the help of insulin, it enters the body's cells where it is utilized as a source of energy.
Insulin is a hormone that comes from a gland located just behind the stomach (pancreas). When you eat, your pancreas secretes insulin into your bloodstream. As insulin circulates, it acts like a key that unlocks microscopic doors that allow sugar to enter your cells.
Insulin 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. This 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, including:
- 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 circumference can indicate insulin resistance. The risk goes up for men with waists larger than 40 inches around and for women with waists larger than 35 inches.
- 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 as you get older, especially after age 45. This may be because people tend to exercise less, lose muscle mass and gain weight as they age.
- Family history. The risk of prediabetes increases if a parent or sibling has type 2 diabetes.
- Race. Although it's unclear why, people of certain races — including African-Americans, Hispanics, American Indians, Asian-Americans and Pacific Islanders — are more likely to develop prediabetes.
- Gestational diabetes. If you developed gestational diabetes when you were pregnant, your risk of later developing diabetes increases. If you gave birth to a baby who weighed more than 9 pounds (4.1 kilograms), you're also at increased risk of diabetes.
- Polycystic ovary syndrome. For women, having polycystic ovary syndrome — a common condition characterized by irregular menstrual periods, excess hair growth and obesity — increases the risk of diabetes.
- Sleep. Research has linked sleep issues, such as obstructive sleep apnea, to an increased risk of insulin resistance. Sleep apnea is a sleep disorder that causes breathing to be interrupted numerous times during sleep, leading to poor sleep quality. 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 diabetes include:
- High blood pressure
- Low levels of HDL, or the "good," cholesterol
- High levels of triglycerides — a type of fat in your blood
When these conditions — high blood pressure, high blood sugar, and abnormal blood fats and cholesterol — occur together along with obesity, they are associated with resistance to insulin. The combination of three or more of these conditions is often referred to as metabolic syndrome.
Progression to type 2 diabetes is the most serious consequence of untreated prediabetes because type 2 diabetes can lead to other complications, such as:
- High blood pressure
- High cholesterol
- Heart disease
- Kidney disease
Healthy lifestyle choices can help you prevent prediabetes and its progression to type 2 diabetes — even if diabetes runs in your family.
- Eat healthy foods.
- Get more physical activity.
- Lose excess pounds.
The same lifestyle changes that can treat or even reverse prediabetes help prevent the condition, too.