Insulin is made up of many small protein building blocks in a chain, something like a string of pearls. Human insulin that is made with the new technology has the same building blocks as your own, and is not recognized as being different by your body. In beef insulin, three building blocks are different, in pork insulin only one is different. It says so on the box and on the vial label. Or you can ask your doctor or pharmacist, or any member of your healthcare team.
R is regular, or short-acting.
It is a clear liquid. It starts working in your body about a half-hour after you inject it, and it's gone in about 8 hours. In the US, insulin is U-100 strength. Outside the US, you might see U-40 insulin, which is not as strong. Your doctor or healthcare team will work with you to find out which is the best insulin for you.