Insulin is a natural hormone produced by the pancreas by the islets of Langerhans that regulates the amount of glucose in the blood. For a multitude of reasons such as diabetes, people become insulin dependent meaning they need synthetic insulin that is made in a lab to survive. There are several types of insulins the work differently from one another. Humalog is the most common rapid acting insulin that takes 10 - 30 minutes to reach the bloodstream and works for 3 to 5 hours before it peaks. Lantis is the most common long acting insulin that takes 30 minutes to an hour to reach the bloodstream and works for a full 24 hours. There are many other types of long and rapid acting insulin like Novolog (rapid acting) and Levemir (long acting) but they are not as common. All of these other forms are made up in a science lab and are needed for individuals who have problems with their pancreas to survive without it people would die.