Unlike the limited selection of insulins Dr. Elliott P. Joslin had to work with, today we have a range of alternatives to choose from. Instead of coming from pigs or cows, most of our insulin is made in the laboratory using recombinant DNA.(As an interesting aside, the insulins used for our pets with diabetes usually still come from the pancreas of animals) .
The insulins we have today fit into one of three broad categories: basal, bolus, and mixed basal-bolus insulin. Basal insulins after being injected, dissociate slowly in the fatty tissue to provide a constant stream of insulin into the circulation throughout the day. They help reduce the amount of glucose secreted by the liver, thereby keeping glucose levels steady. The new basal insulins last approximately 24 hours and are given once or twice a day.
Currently we have three basal insulins available in the United States: Lantus®, Levemir® and NPH. (Lantus® and Levemir® are brand names, NPH is a generic) Lantus® and Levemir® are categorized as long-acting insulins because they can be given once- a -day to cover a 24-hour period. (In people with type 1 diabetes, Levemir® and sometimes Lantus® is given twice per day to avoid reduction in efficacy in the waning hours before the next dose is due) Both are flat, peakless insulins. Peakless insulin works with the same intensity throughout the life of the dose. This has some advantages for people with diabetes because they can calculate approximately how much basal is working per hour by simply dividing their dose by 24. The advent of peakless basal insulins freed people from having to have fixed-snack times that match the insulin peak.
Today most people use Lantus® or Levemir ®as their basal insulin. However, there are still some people who continue to use NPH. NPH, although used as basal insulin, is not truly long-acting. It lasts between 14 and 16 hours. It has been in existence much longer than the other two. Because it does have a peak, NPH is the favored insulin for people who have strong DAWN effects – very high blood glucose in the morning hours- such as women with gestational diabetes.
Bolus insulins are used to cover the rise in blood glucose following a meal or to “correct” a high blood glucose reading back to normal. Today we have the option of using regular insulin which is short-acting insulin or a trio of fast-acting insulins: Novolog®, Humalog® or Apidra®. Regular takes longer to get going than the fast-acting insulins so it isn’t as convenient to use. However it can be a bonus for people who eat high fat meals on a regular basis or for those who have gastroparesis (nerve damage to the gastrointestinal tract) because it lasts for a longer time than fasting acting insulin. Fast acting insulins work for about four hours whereas regular lasts up to eight hours.
Mixed dose insulins combine basal insulin (an analog of NPH) with fasting acting insulin. This incorporates the features of bolus and basal insulin in one injection. They are usually given twice per day at breakfast and dinner. Although more convenient than dosing basal and bolus insulin separately, they do not allow patients as much flexibility. Since they come in fixed amounts of bolus to basal, dosing isn’t as precise. Mixed dose insulin is often used in the elderly or with people who do not wish to take more than two injections per day.