Insulin has changed over the years and was insulin extracted from the pancreas of cattle and pigs until the 1980’s when it could be genetically engineered. There is a difference in each of the types of insulin, the pork insulin has a different type of amino acid than the insulin from cattle insulin which has three different amino acids.

The genetically engineered insulin also has amino acids and today the animal insulin is highly purified and labeled as natural insulin’s. 

Human insulin is another choice, and is manufactured using DNA technology and can be made in an unlimited supply because it does not depend on animals or human insulin from the pancreas.  This process is simple cells like bacteria.