Insulin has come a long way since our grandparents days. There was a time when insulin was extracted from pig and cow pancreas. Because this type of insulin was not identical to human insulin diabetics sometimes had allergic reactions and often developed antibodies to these preparations which made their insulin less effective over time. Today's insulins are largely made through genetic engineering techniques that allow us to make insulin that is identical to human insulin. By combining the insulin with other molecules scientists have been able to make insulins that vary in their duration of action allowing for some quick acting insulins that last for just a short time and other insulins that last an entire day.

In addition to various types of insulin, newer preparations are also much easier to use. In the past insulin came in vials that had to be refrigerated and each days dose had to be carefully drawn up in a new syringe. Today many insulin preparations come packaged in a pen which can be stored at room temperature for weeks. Patients just dial in their dose and inject. The needle has to be changed with each dose but even the needles have been improved. Today's needles are short and as fine as a hair so that injecting insulin is nearly painless.
Insulin is made in the pancreas. During the day the pancreas constantly releases an amount of insulin known as the Basal Insulin Secretion. This happens even if we are not eating anything because insulin is required to get glucose into the cells where it is used for energy. Even if we have not eaten anything our liver keeps our glucose at the needed levels by making and releasing glucose and the basal insulin levels maintained by the pancreas keep our sugar levels balanced. When we eat something the rise in blood sugar is detected by the pancreas which then releases a surge of insulin in response to each meal.

Type I diabetics frequently have no pancreatic function left.  Type I diabetics therefor usually need to replace their basal insulin as well as the after meal insulin spikes with injections of insulin requiring multiple injections with different types of insulin during the course of the day. By contrast, Type II diabetics usually have some pancreatic insulin secretion of their own but can't make enough so often they may only need to replace their basal insulin level once a day with long acting insulin letting the pancreas handle the necessary insulin surges after meals.

Long Acting Insulin

Long acting insulin preparations are designed for once a day dosing. These insulins start working in an hour, have no real peak,  and last for 20-26 hours
  • Levemir
  • Lantus

Intermediate Acting

These insulin preparations have an onset of action in 1-3 hours, peak at 8  hours, and last for 12-16 hours.
  • Humulin N
  • Novolin N

Short Acting

These insulin preparations begin to work in 30-60 minutes, peak at 2-4 hours, and last 5-8 hours
  • Humulin R
  • Novolin R

Rapid Acting

These insulin preparations begin to work in 15 minutes, peak at 30-90 minutes, and last 3-5 hours
  • Humalog
  • Novolog

Mixed Preparations

Mixed preparations have a mixture of  intermediate acting insulin combined with either short or rapid acting insulin.
  • Humulin 70/30 and Humulin 50/50
  • Novolin 70/30
  • Humalog 75/25 and Humalog 50/50
  • Novalog 70/30

Product information

Levemir Flexpen

Lantus Solostar Pen