There are several forms of diabetes. Scientists are still defining and categorizing some of these variations and establishing their prevalence in the population. Types of diabetes include:

• Type 1 diabetes. An autoimmune disease in which the immune system mistakenly destroys the insulin-making beta cells of the pancreas. It typically develops more quickly than other forms of diabetes. It is usually diagnosed in children and adolescents, and sometimes in young adults. To survive, patients must administer insulin medication regularly.
  
  Type 1 diabetes used to be called juvenile diabetes and insulin-dependent diabetes mellitus (IDDM). However, those terms are not accurate because children can develop other forms of diabetes, adults sometimes develop type 1, and other forms of diabetes can require insulin therapy.
  
  A variation of type 1 that develops later in life, usually after age 30, is called latent autoimmune diabetes of adulthood (LADA).
  
  Sometimes patients with autoimmune diabetes develop insulin resistance because of weight gain or genetic factors. This condition is known as double diabetes.
  
  
• Type 2 diabetes. A disorder of metabolism, usually involving excess weight and insulin resistance. In these patients, the pancreas makes insulin initially, but the body has trouble using this glucose-controlling hormone. Eventually the pancreas cannot produce enough insulin to respond to the body’s need for it.
  
  Type 2 diabetes is by far the most common form of diabetes, accounting for 85 to 95 percent of cases in developed nations and an even higher percentage in developing nations, according to the International Diabetes Federation.
  
  This disease may take years or decades to develop. It is usually preceded by prediabetes, in which levels of glucose (blood sugar) are above normal but not high enough yet for a diagnosis of diabetes. People with prediabetes can often delay or prevent the escalation to type 2 diabetes by losing weight through improvements in exercise and diet, as the Diabetes Prevention Program and other research projects have demonstrated.
  
  Type 2 diabetes used to be called adult-onset diabetes and non-insulin-dependent diabetes mellitus (NIDDM). Those terms are not accurate because children can also develop this disease, and some patients require insulin therapy.
  
  
• Gestational diabetes. A temporary metabolic disorder that any previously nondiabetic woman can develop during pregnancy, usually the third trimester. Hormonal changes contribute to this disease, along with excess weight and family history of diabetes. About 4 percent of pregnant women develop gestational diabetes, according to the American Diabetes Association.
  
  Gestational diabetes can cause problems for the mother and baby, including preeclampsia, premature delivery, macrosomia (oversized infant), and jaundice and breathing difficulties in the infant. This disease typically ends when the pregnancy does, but it increases the risk of type 2 diabetes later in life for the mother and the child.
  
  
• Secondary diabetes. Diabetes caused by another condition. The many potential sources of secondary diabetes range from diseases such as pancreatitis, cystic fibrosis, Down syndrome and hemochromatosis to medical treatments including corticosteroids, other immunosuppressives, diuretics and pancreatectomy.
  
  
• Maturity-onset diabetes of the young (MODY). An uncommon disease caused by a genetic defect inherited from a parent. It is usually diagnosed before age 25 in people of normal weight. MODY is sometimes classified as a form of type 2 or secondary diabetes but is often considered a separate condition.

There are also rare syndromes (clusters of conditions) that include diabetes, notably:

• Wolfram syndrome. A genetic disorder that involves insulin-dependent diabetes, vision problems, deafness and diabetes insipidus.
  
  
• Autoimmune polyglandular syndrome (APS). Group of autoimmune endocrine diseases. Two of the three forms of APS feature type 1 diabetes.
  
  

Unstable diabetes, also known as brittle or labile diabetes, is a term that may be used to describe any case of poorly controlled diabetes regardless of the type.

All of these conditions involve diabetes mellitus (“sugar diabetes”). Diabetes insipidus (“water diabetes”) is an unrelated endocrine system disorder in which the kidneys release too much water.