Diabetes mellitus (or diabetes) is a chronic, lifelong condition that affects your body’s ability to use the energy found in food. There are three major types of diabetes: type 1 diabetes, type 2 diabetes, and gestational diabetes.

All types of diabetes mellitus have something in common. Normally, your body breaks down the sugars and carbohydrates you eat into a special sugar called glucose. Glucose fuels the cells in your body. But the cells need insulin, a hormone, in your bloodstream in order to take in the glucose and use it for energy. With diabetes mellitus, either your body doesn’t make enough insulin, it can’t use the insulin it does produce, or a combination of both.

Since the cells can’t take in the glucose, it builds up in your blood. High levels of blood glucose can damage the tiny blood vessels in your kidneys, heart, eyes, or nervous system. That’s why diabetes — especially if left untreated — can eventually cause heart disease, stroke, kidney disease, blindness, and nerve damage to nerves in the feet.

Type 1 diabetes is also called insulin-dependent diabetes. It used to be called juvenile-onset diabetes, because it often begins in childhood.

This type of diabetes may be caused by a genetic predisposition. It could also be the result of faulty beta cells in the pancreas that normally produce insulin.

A number of medical risks are associated with type 1 diabetes. Many of them stem from damage to the tiny blood vessels in your eyes (called diabetic retinopathy), nerves (diabetic neuropathy), and kidneys (diabetic nephropathy). Even more serious is the increased risk of heart disease and stroke.

Treatment for type 1 diabetes involves taking insulin, which needs to be injected through the skin into the fatty tissue below. The methods of injecting insulin include:

• Syringes
• Insulin pens that use pre-filled cartridges and a fine needle
• Jet injectors that use high pressure air to send a spray of insulin through the skin
• Insulin pumps that dispense insulin through flexible tubing to a catheter under the skin of the abdomen

A periodic test called the A1C blood test estimates glucose levels in your blood over the previous three months. It’s used to help identify overall glucose level control and the risk of complications from diabetes, including organ damage.

Having type 1 diabetes does require significant lifestyle changes that include:

• Frequent testing of your blood sugar levels
• Careful meal planning
• Daily exercise
• Taking insulin and other medications as needed

People with type 1 diabetes can lead long, active lives if they carefully monitor their glucose, make the needed lifestyle changes, and adhere to the treatment plan.

By far, the most common form of diabetes is type 2 diabetes, accounting for 95% of diabetes cases in adults. Some 26 million American adults have been diagnosed with the disease.

Type 2 diabetes used to be called adult-onset diabetes, but with the epidemic of obese and overweight kids, more teenagers are now developing type 2 diabetes. Type 2 diabetes was also called non-insulin-dependent diabetes.

Type 2 diabetes is often a milder form of diabetes than type 1. Nevertheless, type 2 diabetes can still cause major health complications, particularly in the smallest blood vessels in the body that nourish the kidneys, nerves, and eyes. Type 2 diabetes also increases your risk of heart disease and stroke.

With Type 2 diabetes, the pancreas usually produces some insulin. But either the amount produced is not enough for the body’s needs, or the body’s cells are resistant to it. Insulin resistance, or lack of sensitivity to insulin, happens primarily in fat, liver, and muscle cells.

People who are obese — more than 20% over their ideal body weight for their height — are at particularly high risk of developing type 2 diabetes and its related medical problems. Obese people have insulin resistance. With insulin resistance, the pancreas has to work overly hard to produce more insulin. But even then, there is not enough insulin to keep sugars normal.

There is no cure for diabetes. Type 2 diabetes can, however, be controlled with weight management, nutrition, and exercise. Unfortunately, type 2 diabetes tends to progress, and diabetes medications are often needed.

An A1C test is a blood test that estimates average glucose levels in your blood over the previous three months. Periodic A1C testing may be advised to see how well diet, exercise, and medications are working to control blood sugar and prevent organ damage. The A1C test is typically done a few times a year.

According to the National Institutes of Health, the reported rate of gestational diabetes is between 2% to 10% of pregnancies. Gestational diabetes usually resolves itself after pregnancy. Having gestational diabetes does, however, put mothers at risk for developing type 2 diabetes later in life. Up to 10% of women with gestational diabetes develop type 2 diabetes. It can occur anywhere from a few weeks after delivery to months or years later.

With gestational diabetes, risks to the unborn baby are even greater than risks to the mother. Risks to the baby include abnormal weight gain before birth, breathing problems at birth, and higher obesity and diabetes risk later in life. Risks to the mother include needing a cesarean section due to an overly large baby, as well as damage to heart, kidney, nerves, and eye.

• Careful meal planning to ensure adequate pregnancy nutrients without excess fat and calories
• Daily exercise
• Controlling pregnancy weight gain
• Taking diabetes insulin to control blood sugar levels if needed

A few rare kinds of diabetes can result from specific conditions. For example, diseases of the pancreas, certain surgeries and medications, or infections can cause diabetes. These types of diabetes account for only 1% to 5% of all cases of diabetes.