Causes of Diabetes
What is diabetes?Diabetes is a complex group of diseases with a variety of causes. People with diabetes have high
blood glucose, also called high blood sugar or hyperglycemia.
Diabetes is a disorder of metabolism—the way the body uses digested food for energy. The
digestive tract breaks down carbohydrates—sugars and starches found in many foods—into
glucose, a form of sugar that enters the bloodstream. With the help of the hormone insulin, cells
throughout the body absorb glucose and use it for energy. Diabetes develops when the body
doesn’t make enough insulin or is not able to use insulin effectively, or both.
Insulin is made in the pancreas, an organ located behind the stomach. The pancreas contains
clusters of cells called islets. Beta cells within the islets make insulin and release it into the blood.
If beta cells don’t produce enough insulin, or the body doesn’t respond to the insulin that is
present, glucose builds up in the blood instead of being absorbed by cells in the body, leading to
prediabetes or diabetes. Prediabetes is a condition in which blood glucose levels or A1C levels—
which reflect average blood glucose levels—are higher than normal but not high enough to be
diagnosed as diabetes. In diabetes, the body’s cells are starved of energy despite high blood
Islets within the pancreas contain beta cells, which
make insulin and release it into the blood.
8/22/2016 Causes of Diabetes | NIDDK
Over time, high blood glucose damages nerves and blood vessels, leading to complications such
as heart disease, stroke, kidney disease, blindness, dental disease, and amputations. Other
complications of diabetes may include increased susceptibility to other diseases, loss of mobility
with aging, depression, and pregnancy problems. No one is certain what starts the processes
that cause diabetes, but scientists believe genes and environmental factors interact to cause
diabetes in most cases.
The two main types of diabetes are type 1 diabetes and type 2 diabetes. A third type,
gestational diabetes, develops only during pregnancy. Other types of diabetes are caused by
defects in specific genes, diseases of the pancreas, certain drugs or chemicals, infections, and
other conditions. Some people show signs of both type 1 and type 2 diabetes.