Type 1 diabetes develops when your body no longer makes the insulin it needs to regulate blood glucose levels.
In the normal digestive process, your body breaks down much of the food you eat into glucose, a simple sugar that's stored in your body and used for energy.
Diabetes is a disease that develops when your pancreas doesn't make enough insulin, or your body doesn't use insulin properly — resulting in high blood glucose levels, which can cause a range of health issues.
There are several types of diabetes: Type 1 and type 2 diabetes are the most common.
Type 1 diabetes develops when the body produces little to no insulin. It’s considered an autoimmune disorder, meaning that the immune system erroneously attacks and destroys the pancreatic beta cells that produce insulin.
Type 1 — previously known as insulin-dependent diabetes, or juvenile-onset diabetes (because it often develops at a young age) — accounts for about 5 percent of all diabetes diagnoses, according to the Centers for Disease Control and Prevention (CDC).
Type 2 diabetes develops when liver, muscle, and fat cells don't respond properly to insulin and become "insulin resistant." Glucose doesn't enter the cells as efficiently as before, and instead builds up in the bloodstream.
In type 2, the pancreas responds to these increased blood glucose levels by producing more insulin. Eventually, however, it can no longer make enough insulin to handle spikes in glucose levels — such as what happens after meals.
Type 2 diabetes accounts for 90 to 95 percent of all diagnosed cases of diabetes, according to the CDC.
In 2012, an estimated 29.1 million people in the United States — 9.3 percent of the population — had diabetes, according to the American Diabetes Association.
However, of these cases, only 1.25 million were type 1 diabetes.
Type 1 diabetes is one of the most common chronic diseases of childhood, according to a 2014 report in The Lancet journal.
It most often arises in children 5 to 7 years old, and near or during puberty, but can strike at any age from infancy on.
Some data suggests that type 1 diabetes affects males and females equally, but it may be slightly more common in males, according to the 2014 report.
It's unknown exactly what causes type 1 diabetes.
Studies suggest that people with the disorder have a defect in their immune system — specifically in the bone marrow and thymus (an organ of the immune system) — and in pancreatic beta cells, all of which contribute to the loss of insulin production, according to the report in The Lancet.
Possible risk factors for type 1 diabetes include:
Overall, people with type 1 diabetes have a decreased life expectancy, according to a 2015 study in the Journal of the American Medical Association (JAMA).
More specifically, men with type 1 diabetes have a life expectancy about 11 years shorter than that of men who don't have the disease. For women, this decrease in life expectancy is 13 years, the JAMA study found.
But life expectancy may depend on how well the condition is managed.
In a separate JAMA study, also from 2015, researchers found that people with type 1 diabetes who underwent intensive treatment for 6.5 years experienced a modestly reduced risk of complications and a lower overall risk of death.