Broadly speaking, there’s insulin in solution (insulin-R or regular insulin) and crystalline insulin. Insulin-R is relatively short acting and is frequently us

Broadly speaking, there’s insulin in solution (insulin-R or regular insulin) and crystalline insulin. Insulin-R is relatively short acting and is frequently used in acute therapy or intensive care. It used to be the only type, and can be used in a mode where it’s given before a meal and as needed. Insulin-N (NPH, neutral protamine Hagedorn insulin) and protamine zinc insulin (PZI) are the first generation crystalline insulins. They have longer lasting (baseline) effects as well as peaking effects that allow them to be given easily on schedule based on the sizes of meals. There’s a variety of modern insulins now, which are substituted with different amino acids to give them different effects. Insulin glargine and insulin detemir are the most popular. They are supposed to have blunted peaks and are given at regular intervals such as every 24 hours. They mimic the baseline insulin secretion. Insulin pumps are also available that monitor blood sugar and secrete insulin to keep it controlled. There are also experimental “artificial pancreases” that will also secrete glucagon. Another comment mentions that cheap insulin can be just as good. This is true but it requires a careful lifestyle. Messing up is more common and if you’re on your own you may be unable to help yourself, e.g. comatose. Currently, insulin-N and -R are cheap. Detemir and glargine are constantly going up in price despite the existence of multiple suppliers of glargine. (This sort of implicit agreement without actual price fixing is common in the pharmaceutical industry). Essentially, the competitor is a small fraction cheaper, can take some of the market, but most people will continue writing and filling scripts for the incumbent because it’s what they know, on the formulary, etc. I’m not sure of the use of PZI in human medicine. It’s popular in my patients, as is glargine.