Diabetes mellitus type 1 (Type 1 diabetes, Type I diabetes, T1D, IDDM) is a form of diabetes mellitus. Type 1 diabetes is an autoimmune disease that results in the permanent destruction of insulin producing beta cells of the pancreas. Type 1 is lethal unless treatment with exogenous insulin via injections replaces the missing hormone.
Type 1 diabetes (formerly known as “childhood”, “juvenile” or “insulin-dependent” diabetes) is not exclusively a childhood problem: the adult incidence of Type 1 is significant — many adults who contract Type 1 diabetes are misdiagnosed with Type 2 due to the misconception of Type 1 as a disease of children — and since there is no cure, Type 1 diabetic children will grow up to be Type 1 diabetic adults.
There is currently no preventive measure that can be taken against type 1 diabetes. Most people affected by type 1 diabetes are otherwise healthy and of a healthy weight when onset occurs, but they can lose weight quickly and dangerously, if not diagnosed in a relatively short amount of time. Diet and exercise cannot reverse or prevent type 1 diabetes. However, there are clinical trials ongoing that aim to find methods of preventing or slowing its development.
The most useful laboratory test to distinguish Type 1 from Type 2 diabetes is the C-peptide assay, which is a measure of endogenous insulin production since external insulin (to date) has included no C-peptide. However, C-peptide is not absent in Type 1 diabetes until insulin production has fully ceased, which may take months. The presence of anti-islet antibodies (to Glutamic Acid Decarboxylase, Insulinoma Associated Peptide-2 or insulin), or lack of insulin resistance, determined by a glucose tolerance test, would also be suggestive of Type 1. As opposed to that, many Type 2 diabetics still produce some insulin internally, and all have some degree of insulin resistance.
Testing for GAD 65 antibodies has been proposed as an improved test for differentiating between Type 1 and Type 2 diabetes.