What Are the Differences Among Type 1, Type 2 and Gestational Diabetes?

You may think you know what diabetes is. But do you know there are actually several types of diabetes, each with its own causes and risk factors? It's important to understand the different types because so many Americans live with the disease -- 29 million people in the U.S., or 9 percent of the population, according to the American Diabetes Association. Diabetes experts expect that number to grow as obesity becomes a bigger health problem, as being overweight or obese is more likely to lead to diabetes.

Here are the basic differences among prediabetes, Type 1 diabetes, Type 2 diabetes and gestational diabetes.

Prediabetes

When you have prediabetes, your blood sugar is high enough to indicate that you may one day develop a type of diabetes called Type 2 diabetes. "You have one step in the door to diabetes," says Angela Ginn-Meadow, a senior diabetes educator at the University of Maryland Center for Diabetes and Endocrinology in Baltimore. Prediabetes is a major problem in the U.S., as 86 million Americans have it, according to the American Diabetes Association.

Doctors diagnose prediabetes by looking at your blood sugar numbers. Fasting blood sugar is a test of the glucose (a type of sugar) in your blood after you haven't eaten for at least 12 hours. A fasting blood sugar between 100 and 125 indicates prediabetes.

[See: The 12 Best Diets to Prevent and Manage Diabetes.]

Another sign of prediabetes is a hemoglobin A1C number between 5.7 and 6.4. Hemoglobin A1C indicates your average blood sugar over a three-month period, and it's determined through a blood test.

Without a test of your blood sugar or A1C, you may not know you have prediabetes. The good news: Once you do know, you still have time to make lifestyle changes so you don't develop Type 2 diabetes, Ginn-Meadow says. Lose weight, exercise at least 150 minutes a week, make healthier food choices and look for programs like the National Diabetes Prevention Program from the Centers for Disease Control and Prevention.

If you lose 5 percent to 10 percent of your body weight, you can reduce your chances of developing Type 2 diabetes by 60 percent, says Grace Derocha, a certified diabetes educator and registered dietitian with Blue Cross Blue Shield of Michigan.

Type 1 Diabetes

When you have Type 1 diabetes, your body does not produce insulin, a hormone. Your body uses insulin to get glucose, a sugar it uses from foods you eat to get energy. Type 1 diabetes is often diagnosed in children and young adults because people who have it are often born with it. However, doctors can diagnose it in adults. You're more likely to get Type 1 diabetes if you have a family member who has it, such as a parent or sibling.

When you have Type 1 diabetes, the way your body stores extra blood sugar is not properly controlled, Derocha says. This is why you need to use insulin to help manage your diabetes and control your blood sugar. "Insulin is key to storing extra blood sugar," she says.

If left untreated, Type 1 diabetes can affect your body in many ways and even kill you. You could experience vision loss, nerve damage and heart and kidney disease. Taking insulin to help control your Type 1 diabetes and seeing your doctor regularly can help prevent these serious health consequences.

Type 2 Diabetes

If you have Type 2 diabetes, your body either does not make enough insulin or your body is not using insulin properly. This is different from Type 1 diabetes because with Type 1, your body does not make insulin at all. Another difference is that Type 2 diabetes is caused more by unhealthy life choices, such as not exercising, eating certain unhealthy foods and gaining too much weight.

[See: The 12 Best Heart-Healthy Diets.]

While Type 1 diabetes often has sudden symptoms such as frequent urination, feeling tired or even feeling like you have the flu, Type 2 takes longer to develop. In fact, you may not even know you have Type 2 diabetes until the symptoms -- which include increased thirst or hunger and unexplained weight loss -- are frequent or until you have your blood sugars tested.

Type 2 diabetes is on the rise around the globe, and the majority of people in the U.S. with diabetes have Type 2. Derocha calls Type 2 diabetes "diabesity" because of the disease's common association with obesity. Still, not everyone with Type 2 diabetes is overweight.

Although eating habits, exercise and weight can affect your risk for developing Type 2 diabetes, you are at a higher risk if you have family members with Type 2 diabetes. Type 2 diabetes is also common as you get older -- Ginn-Meadow says her grandfather was diagnosed with it at age 86.

You can make changes in your life to help keep your blood sugar under control when you have Type 2 diabetes. "Eating healthy, exercising, getting enough sleep and managing stress are important to decrease insulin resistance and control the blood sugar," says Dr. Gregory Dodell, an assistant professor of endocrinology, diabetes and bone disease at Mt. Sinai School of Medicine who is also in private practice at Central Park Endocrinology in New York.

Sometimes, people with Type 2 diabetes (as well as prediabetes and gestational diabetes) take oral medications to help control their blood sugar. If oral medications don't work, you may need to use insulin.

The type of diabetes that you have -- be it Type 1 or Type 2 -- does not change over time, Ginn-Meadow says. "You'll always have Type 1 or Type 2. Type 2 doesn't become Type 1," she says.

[See: Got Diabetes? Why You Must Protect Your Feet.]

Gestational Diabetes

Gestational diabetes develops during pregnancy. This is different from having diabetes and then becoming pregnant, Ginn-Meadow says.

When you have gestational diabetes, your body doesn't produce the right amount of insulin. "You gain weight, and the pancreas can't produce insulin [quickly enough]," Derocha says.

Gestational diabetes is diagnosed with an oral glucose test done on or after the 24th week of pregnancy. A healthy diet and regular physical activity can help keep your blood sugar under control, along with regular visits to your doctor. Some expectant mothers also need oral medications or insulin.

Your gestational diabetes will probably go away after you have your baby. Doctors will reevaluate you about six weeks after you give birth to make sure you no longer have diabetes.

However, women who develop gestational diabetes and their children are at a higher risk for developing Type 2 diabetes after pregnancy, Dodell says.

Vanessa Caceres is a Health freelancer for U.S. News. She's a nationally published health, travel and food writer, and she has an undergraduate degree in journalism and psychology from Hampshire College and a graduate degree in linguistics/bilingual education from Georgetown University. Connect with her on Twitter at @FloridaCulture.