Prediabetes: What You Need to Know About Its Causes, Symptoms & Treatment

Although about 1 in 3 American adults has prediabetes, most don't know it.

"As with every chronic, prevalent disease, it's incredibly important to understand who's at particularly high risk of progressing from prediabetes to diabetes," Dr. Giulio Romeo, medical director of the Joslin Diabetes Center in Boston, explained in Harvard Health.

Discover how medical experts define prediabetes, and learn about its causes, symptoms and the treatment options for the best health outcomes.

What is prediabetes?

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says prediabetes results when your blood glucose (sugar) levels are higher than normal, but not yet high enough to be considered type 2 diabetes.

So how does this happen?

It starts with a hormone called insulin, which is produced by your pancreas. Insulin is needed to help blood glucose gain entry into your cells so it can provide energy for cellular activities.

In prediabetes, your cells develop insulin resistance, making it difficult for the hormone to transfer glucose into your cells. This triggers your pancreas to produce even more insulin.

Over time, your pancreas loses the ability to produce enough insulin to keep up with the amount of glucose that needs to be transferred from your blood into your cells. This can drive up your blood sugar (glucose) to prediabetes levels.

Harvard Health and the NIDDK note there are three types of blood glucose tests to measure your blood glucose levels:

• A1C measures your average blood sugar for the past two to three months: A reading between 5.7% and 6.4% is considered prediabetes.
• A fasting blood glucose test measures how your body processes blood glucose at night: A reading of 100-125 milligrams (mg) per deciliter (dL) is considered prediabetes.
• A glucose tolerance test uses blood sugar samples taken before and after you drink a sugar mixture to measure how your body processes sugar after eating. A reading of 141-199 mg/dL two hours after drinking the mixture is considered prediabetes.

"Anyone whose blood sugar falls into the prediabetes range is going in only one direction unless changes are made," Emma Samuels Grinblatas, a registered dietitian at Beth Israel Deaconess Medical Center, told Harvard Health.

What causes prediabetes?

While scientists don’t know the exact causes of prediabetes, excess weight and lack of exercise are two of the leading risk factors. The NIDDK warns you may also be at a higher risk for developing prediabetes if you’re:

• Over age 44
• Have a sibling, child or parent with diabetes
• Are diagnosed with high cholesterol or high blood pressure
• Have a history of heart disease, stroke, polycystic ovarian syndrome or gestational diabetes

People of certain ethnicities may also have an elevated risk of developing prediabetes, including:

• African Americans
• Native Hawaiians
• Hispanic/Latinos
• Asian Americans
• American Indians
• Pacific Islander Americans
• Alaskan Natives

Prediabetes symptoms

"While we like to classify things in buckets, the truth is that prediabetes and type 2 diabetes are often on a continuum. It's the same process across different stages," Romeo explained. "Sometimes people are on the brink, so they notice certain signs even if they don't, by the book, have type 2 diabetes."

While symptoms aren’t typical, the NIDDK notes some people with prediabetes may notice:

• Darker skin on the back and sides of the neck or near the armpits
• Growth of new skin tags
• Changes in how the eye works due to damaged blood vessels (retinopathy)

Prediabetes treatments

Learning how to reverse prediabetes through healthier diet and lifestyle choices is one of the main treatment strategies recommended by the NIDDK.

A study of more 1,000 people published in the journal JAMA Internal Medicine revealed that even “modest” lifestyle changes, including losing 4.5 to 6.5 pounds and increasing exercise, reduced the risk of developing diabetes by 40% to 47%.

Johns Hopkins Medicine diabetes educator and clinical dietitian Tara Seymour suggests several prediabetes diet strategies that can help, including eating a Mediterranean diet and limiting your sugar intake to no more than 5% of your total calories per day.

Seymour also suggests these prediabetes self-care strategies:

• Get plenty of sleep to help reduce sugar cravings.
• Exercise moderately at least 150 minutes per week, or try for 10,000 steps per day.
• Use alcohol and tobacco in moderation.
• Keep track of your A1C, cholesterol and blood pressure readings.

The NIDDK also notes that your doctor may prescribe a medicine called metformin for your prediabetes to help delay the onset of diabetes.

Living with prediabetes

“Adopting a well-balanced diet, staying active [and] controlling your weight can put you in control, enabling you to arrest or even reverse the process,” Seymour said. “I like this quote from the CDC [Centers for Disease Control and Prevention]: ‘Life doesn’t always give you the time to change the outcome. Prediabetes does.'"