Why is insulin injected?

Insulin is normally made by the beta cells in the pancreas. If the body is short on insulin, it must be injected to keep levels up, hour by hour. It cannot be taken in pills as the molecule is too fragile to survive digestion.

Normally, insulin is produced by the body to regulate blood sugar level. For diabetics, however, the beta cells become dysfunctional and are either destroyed or do not make enough insulin, or the other cells in the body resist insulin and require more of it. As a result, people who are diabetic must inject insulin to maintain their blood sugar level, hour by hour. Because of this, people who are diabetic tend to have a blood with higher level of sugar, or to be unable to lower the sudden rises of blood sugar that occur after eating.