What is prediabetes?

Prediabetes¹, a precursor of diabetes², means that your blood sugar (glucose) levels are higher than normal but not yet high enough to be classified as type 2 diabetes³. Prediabetes can affect both adults and children.

Without making lifestyle changes, people with prediabetes are likely to progress towards developing type 2 diabetes. People with prediabetes may even have some of the signs, symptoms, and complications experienced by those with type 2 diabetes. If you do have prediabetes, the long-term damage caused by the condition (especially to the heart, blood vessels, and kidneys) may already be starting.

Progression from prediabetes to type 2 diabetes, however, isn’t inevitable. Making healthy lifestyle choices like eating healthy foods, getting sufficient exercise, and maintaining a healthy weight can help bring your blood sugar back to a normal level. In some cases, the same lifestyle changes that can help prevent the progression of prediabetes to type 2 diabetes in adults may also help children’s blood sugar levels return to normal.

How common is prediabetes?

According to the CDC, approximately 84.1 million adults⁴ in the United States aged 18 years or older (33.9% of the adult population) had prediabetes in 2015. Nearly half (48.3%) of adults aged 65 years or older had prediabetes.

Among those adults with prediabetes, 11.6% reported being told by a healthcare professional that they had this condition. Of those with prediabetes, 90% don’t know they have it⁵.

Age-adjusted data collected from 2011–2014 indicated that more men than women had prediabetes—36.6% versus 29.3%, respectively.

High blood sugar causes

While the exact cause⁶ of prediabetes is unknown, family history and genetics—as well as inactivity and excess body fat—appear to play an important role in developing the condition. It is also clear that people with prediabetes don’t process sugar (glucose) properly.

Hyperglycemia⁷, or high blood sugar, affects people who have diabetes. The factors that contribute to hyperglycemia in people with diabetes (such as food and physical activity choices) can also contribute to high blood sugar in people who are prediabetic.

Most of the glucose in your body comes from the food you eat. When food is digested, sugar enters the bloodstream. Moving sugar from the bloodstream to the body’s cells requires insulin, which is a hormone made by the pancreas that acts like a key to let blood sugar into cells for use as energy.

High blood sugar occurs when your pancreas doesn’t make enough insulin or your cells become resistant to the actions of insulin (or both). In people with prediabetes, the cells in the body can’t process glucose properly anymore, causing sugar to accumulate in the bloodstream instead of fueling the cells that make up muscles and other tissues.

Too much glucose in your blood can damage your body over time. If left untreated, hyperglycemia can become severe and may lead to serious complications requiring emergency care, such as a diabetic coma⁸. Even if it isn’t severe, chronic (long-term) hyperglycemia can lead to complications affecting the eyes, kidneys, nerves, and heart.

Prediabetes A1C

The A1C test⁹ (also known as the hemoglobin A1C or HbA1c test) is a simple blood test that measures your average blood sugar levels over the past 3 months. This is one of the most common tests used to diagnose prediabetes and diabetes and is also the main test used to help manage diabetes.

When sugar enters the bloodstream, it attaches to hemoglobin (a protein in red blood cells). While everyone has some sugar attached to their hemoglobin, people with higher blood sugar levels have more. The A1C test measures the percentage of your red blood cells that have sugar-coated hemoglobin.

A normal A1C level is below 5.7%. A level of 5.7%–6.4% indicates prediabetes, while a level of 6.5% or more indicates diabetes. Within the 5.7%–6.4% prediabetic range, the higher your A1C, the greater your risk for developing type 2 diabetes.

Higher A1C levels are linked to diabetes complications. If you have diabetes, reaching and maintaining your individual A1C goal is crucial.

Risk factors for prediabetes

The same factors that increase the risk of developing type 2 diabetes increase the risk of developing prediabetes.

Risk factors¹⁰ for prediabetes 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 developing insulin resistance goes up for men with waists larger than 40” and women with waists larger than 35”.
• Diet: Eating red meat and processed meat and consuming high-sugar foods and drinks are 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 physically active you are, the greater your risk for prediabetes. Physical activity helps control your weight, uses up glucose as energy, and makes your cells more sensitive to insulin.
• Age: While diabetes can develop at any age, the risk of developing the condition increases after age 45. This may be attributed to people tending to exercise less, lose muscle mass, and gain weight as they age.
• Family history: Your risk for prediabetes increases if you have a parent or sibling with type 2 diabetes.
• Race and ethnicity: While it is unclear exactly why this is the case, people of certain racial and ethnic groups (including African-Americans, Hispanics, indigenous Americans, Asian-Americans, and Pacific Islanders) are more likely to develop prediabetes.
• Gestational diabetes: If you developed gestational diabetes¹¹ (diabetes that develops during pregnancy), you and your child are at higher risk for 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 (POC)¹²: This common condition—characterized by irregular menstrual periods, excess hair growth, and obesity—increases a woman’s risk for prediabetes.
• Sleep: People with obstructive sleep apnea¹³ (a disorder that disrupts breathing during sleep) have an increased risk of insulin resistance. People who work irregular shifts or night shifts (which may cause sleep problems) also have an increased risk of prediabetes or type 2 diabetes.

Prediabetes symptoms

Prediabetes generally has no signs or symptoms¹⁴. Because it’s possible to have prediabetes for years without any clear symptoms, the condition often goes undetected until serious health problems such as type 2 diabetes show up.

One possible sign that you may be at risk for type 2 diabetes is darkened skin on certain parts of the body, such as the neck, armpits, elbows, knees, and knuckles.

The most obvious signs and symptoms generally show up when you have progressed from prediabetes to type 2 diabetes. These include:

• Increased thirst
• Frequent urination
• Fatigue
• Blurred vision

It’s important to talk to your healthcare provider if you experience any of these symptoms, as he or she will be able to determine whether they could indicate the progression to type 2 diabetes or the presence of any other condition.

Hyperglycemia symptoms

Hyperglycemia associated with diabetes usually doesn’t present symptoms¹⁵ until glucose levels exceed 180–200 milligrams per deciliter of blood (mg/dL).

The symptoms of hyperglycemia tend to develop slowly over several days or weeks. The longer blood sugar levels remain elevated, the more serious the symptoms become. Signs and symptoms of hyperglycemia may not always be evident, however—some people who have had type 2 diabetes for a long time may not show any symptoms, despite elevated blood sugar levels.

The early signs and symptoms of hyperglycemia are similar to those of prediabetes that has progressed or is progressing towards type 2 diabetes. Recognizing these indicators can help you and your healthcare provider to treat your condition properly.

If hyperglycemia goes untreated, it can cause toxic acids called ketones to build up in your blood and urine, causing a condition called ketoacidosis¹⁶.

Later signs and symptoms of severe hyperglycemia include:

• Fruity-smelling breath
• Nausea and vomiting
• Shortness of breath
• Dry mouth
• Weakness
• Confusion
• Abdominal pain
• Coma

Complications from prediabetes

The most serious consequence of prediabetes is the progression of the condition to type 2 diabetes. The long-term complications caused by diabetes develop gradually. The longer you have diabetes—and the less controlled your blood sugar is—the higher the risk of developing complications. Eventually, diabetes complications can be disabling or life-threatening.

Possible complications from diabetes include:

• Cardiovascular disease: Diabetes drastically increases the risk of developing numerous cardiovascular problems, including coronary artery disease¹⁷ with chest pain (called angina¹⁸), heart attack¹⁹, stroke²⁰, and atherosclerosis²¹ (narrowing of the arteries). Diabetes can also affect the heart muscle, causing both systolic and diastolic heart failure²².

• Nerve damage (neuropathy²³): Excess glucose can damage the walls of the tiny blood vessels (capillaries) that nourish your nerves—especially those in your legs and feet. This can cause tingling, numbness, burning, or pain that usually begins at the tips of the toes or fingers and spreads upward. If left untreated, neuropathy can cause the loss of all sensation in the affected limbs.

• Kidney damage (nephropathy²⁴): This serious condition is caused by damage to the millions of tiny blood vessel clusters (glomeruli) in the kidneys that filter waste from your blood. The damaged filter leaks protein, or albumin, into your urine (microalbuminuria²⁵). Severe damage can lead to kidney failure or irreversible end-stage kidney disease.

• Eye damage (retinopathy²⁶): Diabetes can cause damage to the blood vessels of the light-sensitive tissue at the back of the retina, potentially leading to blindness. Diabetes also increases the risk of developing other vision conditions, such as glaucoma.

• Foot damage: Nerve damage in the feet or poor blood flow to the feet increases the risk of various foot complications. If left untreated, cuts and blisters can become seriously infected and heal poorly. These infections may eventually require toe, foot, or leg amputation.

• Skin conditions: Diabetes can leave you more susceptible to skin problems like bacterial and fungal infections.

• Hearing impairment: Hearing problems are more common in people with diabetes—the condition can lead to hearing loss.

• Alzheimer’s disease: Type 2 diabetes may increase your risk of developing Alzheimer’s disease²⁷. The poorer your control over your glucose levels, the greater the risk appears to be.

• Depression: Symptoms of depression²⁸ are common in people with type 1 and type 2 diabetes. Depression can affect your ability to manage your diabetes. It is crucial to manage your prediabetes and share any signs, symptoms, or concerns with your healthcare provider. He or she will be able to diagnose and treat any conditions associated with the progression of prediabetes.