Insulin has come a long way since its initial discovery back in 1922. Once derived only from animals, today's insulins are the result of sophisticated genetic engineering techniques that have allowed researchers to alter the human insulin gene to create a variety of drugs that behave in different ways.

In fact, there are so many insulin options today that figuring out which type does what can be confusing. From the fastest acting to the longest lasting, this guide to insulin will help demystify the drug.

Why is each insulin different?

Click here to download a printable PDF version of this slideshow