There is a lot of confusion on this simple question, partly because of the other names commonly used for these two conditions. Type 1 diabetes has often been called juvenile diabetes, and type 2 is frequently referred to as adult-onset diabetes. But there are plenty of adults who develop type 1 diabetes, and an increasing number of children and adolescents are getting type 2 diabetes. In the same way, type 1 diabetes is sometimes referred to as insulin-dependent diabetes mellitus (IDDM), and type 2 as non-insulin-dependent diabetes mellitus (NIDDM). This is also misleading, because many people with type 2 diabetes require insulin for adequate blood sugar control.
Insulin is a hormone that is responsible for ushering blood glucose (sugar) into cells; if not enough gets into cells, high blood glucose results. As we describe in The Best Life Guide to Managing Diabetes and Pre-Diabetes, there are two main problems with insulin in diabetes: either the body is not making enough insulin, or it is not responding properly to the insulin that is being made, or both.
In simple terms, type 1 diabetes means the body is not making any insulin. The vast majority of people with type 1 have an autoimmune problem causing their diabetes. This means that the body’s immune system-which should be protecting us against invading viruses and bacteria-instead attacks and destroys the insulin-producing cells in the pancreas. Because insulin is necessary for survival, and because people with type 1 diabetes make no insulin, they must take insulin.
Type 2 diabetes is much more common, but is also a little more complicated. People with type 2 diabetes start out making plenty of insulin, but their bodies do not respond to it properly. This is termed insulin resistance, and it is mostly caused by abdominal obesity. Type 2 diabetes tends to occur in adults. Unfortunately, as children and adolescents become more overweight or obese, more of them are developing insulin resistance, and some are even developing type 2 diabetes. In addition, the amount of insulin made by people with type 2 diabetes tends to decline with time. Over time, many people with type 2 diabetes do not make enough insulin for oral medications to work. These individuals need to be treated with insulin, so it is misleading to call type 2 diabetes “non-insulin dependent.”