Insulin-dependent (Type 1) diabetes is caused by a loss or malfunction of the insulin producing cells, called pancreatic beta cells. Damage to beta cells results in an absence or insufficient production of insulin produced by the body. Most cases of type 1 diabetes have an autoimmune basis, and the immune system mistakenly attacks and destroys beta cells. Since insulin is necessary to sustain life, the missing insulin has to be replaced. The replacement insulin is administered by injection using a syringe or an insulin pump, which delivers the insulin under the skin. (Diabetes Education Online)