Insulin is a naturally occurring, glucose-lowering hormone used by many people with diabetes to control their blood sugar. In people with type 1 diabetes, supplemental insulin makes up for the insulin that is not produced by the body. People with type 2 diabetes may need to take insulin if they cannot maintain adequate blood sugar control with other medications.
Insulin is manufactured to be identical to the insulin produced by the human pancreas. These synthetic insulins can work from a few hours (rapid-acting insulin) to a whole day (long-acting insulin). They are typically injected via a needle or pen.