What is diabetes mellitus?

Diabetes occurs when your body does not make enough insulin. Or it occurs when your body can't use the insulin that is made. It is a chronic (long-lasting) health condition. Your body breaks down most of the food you eat into sugar (glucose) and releases it into your bloodstream. Glucose is the body's main fuel source. Diabetes is called a metabolic disorder because the disease affects the way the body uses food to make blood sugar (glucose). The three main types of diabetes are:

• Type 1 diabetes.Type 1 diabetes is an autoimmune disease. It occurs when your immune system attacks the beta cells in the pancreas that make insulin. This leads to no insulin or a low amount of insulin in the body. It is mostly seen in children or adolescents. People with type 1 diabetes must take insulin every day and check their blood sugars often.

• Type 2 diabetes.Type 2 diabetes occurs because the body can't make enough insulin. Or it occurs because your body can't correctly use insulin. This is called insulin resistance. There is an imbalance between insulin levels and insulin sensitivity. It is thought to affect middle-aged and older adults who have long-lasting high blood sugar (hyperglycemia) due to unhealthy lifestyle and dietary choices. Type 2 diabetes may be controlled with diet, exercise, and weight loss. You may need to take medicine by mouth (oral) or as a shot.

• Gestational diabetes.This is diabetes that occurs during pregnancy in women who have never had diabetes. It is not known why it develops. Blood sugar is high and other symptoms of diabetes occur. In many cases, gestational diabetes goes away after the baby is born. But it increases the risk for type 2 diabetes later in life. The baby is also more likely to have obesity as a child or teen and develop type 2 diabetes later in life.

What is prediabetes?

Prediabetes often occurs before type 2 diabetes. In prediabetes, blood glucose levels are higher than normal, but not high enough to be diagnosed as type 2 diabetes. Prediabetes also increases the risk for type 2 diabetes, heart disease, and stroke. You may be able to delay or prevent type 2 diabetes by making lifestyle changes. These include losing weight if you are overweight and getting more exercise.

How does diabetes affect blood sugar?

Insulin is a hormone. It's made by beta cells in the pancreas. Whenever there is a spike in your blood sugar, such as after meals, your body signals the pancreas to release insulin. Your body needs insulin to move blood sugar (glucose) into the cells, where it is used to carry out many essential processes. Normally, insulin is in the body and ready to move the glucose. But when you have diabetes, the pancreas makes too little or no insulin. Or certain cells in the body don't respond to the insulin that is made (insulin resistance). This causes glucose to build up in the blood. The extra glucose passes into the urine and out of the body. Your body is left without its main source of fuel. Over time, excess glucose can lead to serious health problems, such as heart disease, vision loss, nerve damage, and kidney disease.

What is maturity-onset diabetes in the young (MODY)?

Maturity-onset diabetes of the young (MODY) is a group of different types of inherited diabetes. They occur in teens and young adults. MODY is often at first incorrectly diagnosed as type 1 or type 2 diabetes.

The symptoms of diabetes linked to MODY vary. It depends on the type of MODY diagnosed. MODY 2 seems to be the mildest form of the disease. It often causes only mild high blood sugar (hyperglycemia). It also affects how the body responds to blood sugar. The other forms of MODY may need treatment with insulin, much like type 1 diabetes. Family members of people with MODY are at much greater risk for the condition. Your health care provider may diagnose MODY if 3 generations of your family have been diagnosed with mild diabetes before age 25. It's also more likely if your family members are not obese and are not resistant to insulin.