All people with Type 1 diabetes need insulin. Insulin is typically injected as a shot because it would be destroyed by stomach acid if taken as a pill. Insulin can be taken using a syringe or by an insulin pen. Some people use catheters connected to an insulin pump to continuously infuse rapid-acting insulin. Inhaled insulin is used in some patients with Type 2 diabetes, but not for Type 1. Vials of insulin can be kept at room temperature for 30 days, as long as it does not freeze or get over 90° F. There are four broad classes of insulin:
Long-Lasting (basal) Insulins (last 20 to 24 hours)
Lantus (Insulin glargine) is a clear insulin that lasts 24 hours with almost no peak. It is referred to as a basal insulin since it serves as a base, or the minimum amount of insulin that should be in the bloodstream at all times. Its profile is similar to the basal insulin put out by a non-diabetic pancreas. It is often compared with the basal insulin of an insulin pump.
Levemir (Insulin detemir) is a clear insulin made by Novo Nordisk and is also a basal insulin. Its duration is 20 to 24 hours. It may need to be taken twice daily by some people. There is also some evidence it may help with weight loss.
Ultra Long-Lasting Insulin (lasts up to 72 hours)
Tresiba (Degludec) is also a clear insulin. Although it has some activity over 36 hours, its main activity is over 24 hours. Levels are very consistent, which may help to reduce nighttime lows.
Short-Lasting/Rapid-Acting Insulins (lasts 3 to 4 hours)
These insulins, including Humalog (H) NovoLog (NL) and Apidra (AP), are rapid in onset of activity (10 to 20 minutes) and are short-lasting (three to four hours). Comparatively, regular insulin has a peak activity of approximately two to four hours and lasts effectively six to nine hours. These insulins are usually given to allow sugar to be used by the body immediately after a meal.
The most common insulin injection therapy in the U.S. is the use of a long-lasting insulin (to serve as a base) along with a rapid-acting insulin (administered before meals). This therapy is known as basal (long-lasting)-bolus (rapid-acting) insulin therapy.
Figure 1 shows the activities of this basal-bolus insulin therapy. All three rapid-acting insulins (H, NL and AP) are similar in activity. Although these rapid-acting insulins work more quickly than regular insulin (R), they still do not start working or reach a peak in activity as quickly as desired. This is because the blood sugar level usually peaks approximately 60 minutes after food is eaten, whereas rapid-acting insulins peak at approximately 90 minutes after injection. To match up the peaks of blood glucose and insulin, patients are instructed to perform the injection 20 minutes prior to eating (since eating a meal typically takes 10 minutes to complete).
Intermediate-Lasting Insulin (lasts 12 to 18 hours)
NPH (N) insulin, also referred to as “cloudy” insulin (not clear), is made with a protein that allows it to be absorbed in the body more slowly. Human NPH has its peak activity four to eight hours after the injection in most people. It is often taken twice per day, and if taken in the morning, the peak action usually comes in the midday to afternoon (see figure 2). Human NPH insulin lasts an average of 12 to 18 hours. The peak in NPH insulin activity and the duration of activity may vary in the same person from day to day. NPH is often called “N” on the bottles.
In developing countries, where basal (long-lasting) and rapid-acting insulins are not available, the most frequent therapy used is two injections of intermediate-lasting insulin per day, along with regular (R) insulin before meals.