Depending on a number of factors, individuals vary insulin volume, type, and frequency, to optimize blood glucose management. That there are so many different formulations of insulin is partly intentional, and partly an accident of history. Before insulin, diabetics just died. When the hormone became available in the 1920s, doctors realized patients' needs differed. The existence of so many different insulins helps the doctor tailor a dosage best for a specific individual.
Many patients have specific questions about insulin use.
Insulin works far better when given sufficient time to do its job. Diabetes self-management requires keeping to the established schedule. Too much time, or too little, will cause problems. Exercise of a given muscle area after injection of insulin into that area will cause the insulin to be absorbed faster. Exercise in general burns up blood glucose, lessening the need for insulin to digest it, thus increasing the effect of injected insulin.