The advantage of NPH is its low cost, the fact that you can mix it with short-acting forms of insulin, thereby minimizing the number of injections that must be administered, and that the activity of NPH will peak 4–6 hours after administration, allowing a bedtime dose to balance the tendency of glucose to rise with the dawn, along with a smaller morning dose to balance the lower afternoon basal need and possibly an afternoon dose to cover evening need. A disadvantage of bedtime NPH is that if not taken late enough (near midnight) to place its peak shortly before dawn, it has the potential of causing hypoglycemia. One theoretical advantage of glargine and detemir is that they only need to be administered once a day, although in practice many people find that neither lasts a full 24 hours. They can be administered at any time during the day as well, provided that they are given at the same time every day. Another advantage of long-acting insulins is that the basal component of an insulin regimen (providing a minimum level of insulin throughout the day) can be decoupled from the prandial or bolus component (providing mealtime coverage via ultra-short-acting insulins), while regimens using NPH and regular insulin have the disadvantage that any dose adjustment affects both basal and prandial coverage. Glargine and detemir are significantly more expensive than NPH, lente and ultralente, and they cannot be mixed with other forms of insulin.A short-acting insulin is used to simulate the endogenous insulin surge produced in anticipation of eating.
However, the clinical preparations prepared from such insulins differ from endogenous human insulin in several important respects; an example is the absence of C-peptide which has in recent years been shown to have systemic effects itself. Novo Nordisk has also developed a genetically engineered insulin independently using a yeast process.According to a survey that the International Diabetes Federation conducted in 2002 on the access to and availability of insulin in its member countries, approximately 70% of the insulin that is currently sold in the world is recombinant, biosynthetic human insulin. A majority of insulin used clinically today is produced this way, although clinical experience has provided conflicting evidence on whether these insulins are any less likely to produce an allergic reaction. Adverse reactions have been reported; these include loss of warning signs that patients may slip into a coma through hypoglycemia, convulsions, memory lapse and loss of concentration. However, the International Diabetes Federations position statement from 2005 is very clear in stating that "there is NO overwhelming evidence to prefer one species of insulin over another" and "[modern, highly purified] animal insulins remain a perfectly acceptable alternative. "Since January 2006, all insulins distributed in the U.S. and some other countries are synthetic "human" insulins or their analogues.