Diabetes is a group of diseases in which the body either doesn’t produce enough or any insulin, does not properly use the insulin that is produced, or a combination of both. When any of these things happens, the body is unable to get sugar from the blood into the cells. That leads to high blood sugar levels.

Glucose, the form of sugar found in your blood, is one of your chief energy sources. Lack of insulin or resistance to insulin causes sugar to build up in your blood. This can lead to many health problems.

The three main types of diabetes are:

  • type 1 diabetes
  • type 2 diabetes
  • gestational diabetes

Type 1 diabetes

Type 1 diabetes is believed to be an autoimmune condition. It happens when your immune system mistakenly attacks and destroys the beta cells in your pancreas that produce insulin. The damage is permanent.

What prompts the attack isn’t clear. There may be both genetic and environmental components. Lifestyle factors aren’t thought to play a role.

Type 2 diabetes

Type 2 diabetes starts as insulin resistance. This means your body can’t use insulin efficiently. That stimulates your pancreas to produce more insulin until it can no longer keep up with demand. Insulin production decreases, which leads to high blood sugar.

The exact cause is unknown. Contributing factors may include genetics, lack of exercise, and being overweight. There may also be other health factors and environmental reasons.

Gestational diabetes

Gestational diabetes is due to insulin blocking hormones produced during pregnancy. This type of diabetes only occurs during pregnancy.

Learn more: What you should know about pregestational diabetes »

General symptoms of diabetes include:

  • excessive thirst and hunger
  • frequent urination
  • drowsiness or fatigue
  • dry, itchy skin
  • blurry vision
  • slow healing wounds

Type 2 diabetes can cause dark patches in the folds of skin in your armpits and neck. Since type 2 diabetes often takes longer to diagnose, you may feel symptoms at the time of diagnosis, like pain or numbness in your feet.

Type 1 diabetes often develops more quickly and can cause symptoms like weight loss or a condition called diabetic ketoacidosis. Diabetic ketoacidosis can occur when you have very high blood sugars, but little or no insulin in your body.

Symptoms of both types of diabetes can appear at any age, but generally type 1 occurs in children and young adults. Type 2 occurs in people over the age of 45. But younger people are increasingly being diagnosed with type 2 diabetes due to sedentary lifestyles and an increase in weight.

About 29.1 million people in the United States have diabetes. About 5 to 10 percent of people with diabetes have type 1, while 90 to 95 percent have type 2 diabetes.

The latest figures show that 1.7 million adults were newly diagnosed in 2012. Another 86 million are thought to have prediabetes. But most people with prediabetes don’t know they have the condition.

Prediabetes occurs when your blood glucose is higher than it should be, but not high enough to be diabetes. About 15 to 30 percent of people with prediabetes will develop type 2 diabetes within five years.

You’re more likely to develop diabetes if you have a family history of the disease.

Other risk factors for type 2 diabetes include:

  • having a sedentary lifestyle
  • being overweight
  • having had gestational diabetes or prediabetes

Complications of diabetes generally develop over time. Having poorly controlled blood sugar levels increases the risk of serious complications that can become life-threatening. Chronic complications include:

  • vessel disease, leading to heart attack or stroke
  • eye problems, called retinopathy
  • infection or skin conditions
  • nerve damage, or neuropathy
  • kidney damage, or nephropathy
  • amputations due to neuropathy or vessel disease

Type 2 diabetes may increase the risk of developing Alzheimer’s disease, especially if your blood sugar is not well controlled.

Complications in pregnancy

High blood sugar levels during pregnancy can harm mother and child, increasing the risk of:

  • high blood pressure
  • preeclampsia
  • miscarriage or stillbirth
  • birth defects

No matter what type of diabetes you have, you’ll need to work closely with your doctor to keep it under control.

The main goal is to keep blood glucose levels within your target range. Your doctor will let you know what your target range should be. Targets vary with the type of diabetes, age, and presence of complications. If you have gestational diabetes, your blood sugar targets will be lower than people with other types of diabetes.

Learn more: How to determine your insulin sensitivity factor »

You’ll also need to monitor your blood pressure and cholesterol.

Physical activity is an important part of diabetes management. Ask your doctor how many minutes per week you should devote to aerobic exercise. Diet is also crucial to good control.

Treating type 1

All people with type 1 diabetes must take insulin to live because damage to the pancreas is permanent. There are different types of insulin available with different times of onset, peak, and duration.

Insulin is injected just under the skin. Your doctor will show you how to properly inject and rotate injection sites. You can also use an insulin pump, which is a device worn outside your body that can be programmed to release a specific dose.

You’ll need to monitor your blood sugar levels throughout the day.

If necessary, you can also take medication to control cholesterol, high blood pressure, or other complications.

Treating type 2

Type 2 diabetes is managed with diet and exercise, and can also be treated with a variety of medications to help control blood sugar. The first-line medication is usually metformin (Glumetza, Glucophage, Fortamet, Riomet). This drug helps your body use insulin more effectively. If metformin doesn’t work, your doctor can add other medications or try something different.

You’ll need to monitor your blood sugar levels. You may also need medications to help control blood pressure and cholesterol.

There’s no cure for type 1 diabetes. It requires lifelong disease management. But with consistent monitoring and adherence to treatment, you may be able to avoid some of the more serious complications of the disease.

If you work closely with your doctor and make good lifestyle choices, type 2 diabetes can often be successfully managed.

If you have gestational diabetes, chances are it will resolve after your baby is born though you do have a higher risk of developing type 2 diabetes later in life.

There’s no known prevention for type 1 diabetes.

You can lower your risk of type 2 diabetes if you:

  • control your weight and manage your diet
  • exercise regularly
  • avoid smoking, high triglycerides, and low HDL cholesterol levels

If you had gestational diabetes or have prediabetes, these habits can delay or prevent the onset of type 2 diabetes.