Human Insulin

insulin bottle with syringe

Synthetic human insulin is identical to your own.

However, relative to the rapid-acting insulin analogs, regular human insulin has several undesirable features.

Synthetic human insulin is identical in structure to your own natural insulin. But when it is injected under the skin it doesn’t work as well as natural insulin. This is because injected human insulin clumps together and takes a long time to get absorbed. The activity of this synthetic human insulin is not well synchronized with your body’s needs.

In this section, you will find information about:

Fast-acting injected insulin

Relative to the rapid-acting insulin analogs, Regular human insulin has undesirable features, such as a delayed onset of action, and variable peak and duration of action when it is injected under the skin. Because of this, fewer and fewer medical providers are prescribing Regular insulin. The delayed onset of action is the reason you have to inject the insulin and wait before eating. And the variable duration of action predisposes to low blood sugars long after the meal is over.

Rapid Acting Insulin Analogs - Advantages for Mealtime/Bolus Coverage chart


Regular Human Insulin Peak Time: 2-4 Hours

Intermediate-acting injected insulin

NPH (Neutral Protamine Hagedorn) is an intermediate-acting human insulin that is used to cover blood sugar between meals, and to satisfy your overnight insulin requirement. A fish protein, protamine, has been added to the Regular human insulin to delay its absorption. This long acting insulin is a cloudy suspension that needs to be remixed thoroughly before each injection. Because NPH is a suspension of different sized crystals, it has a very unpredictable absorption rate and action. This results in more frequent low and high blood sugars. The use of NPH has declined with the availability of other long-acting insulin options, specifically, the long-acting insulin analogs, insulin glargine and insulin detemir.

Long Acting Insulin Analog - Advantages for Basal Coverage Chart

Additional information about NPH:

  • An optimal NPH regimen involves small doses before meals (for between-meal insulin coverage), with a larger dose at bedtime (to cover this longer time period). In this regimen, rapid acting insulin analogs need to be given at mealtime or for high sugar correction (ie as bolus therapy).
  • The traditional NPH insulin regimens use two injections of NPH per day. The first dose covers the day and the second dose covers the evening and night. With this basic regimen, Regular insulin also is given before breakfast and dinner.
  • An alternative NPH regimen is to give Regular insulin alone at meals and NPH at bedtime.
  • Other regimens use various combinations of rapid-acting analog insulin or Regular insulin and NPH.


Self-assessment Quiz

Self assessment quizzes are available for topics covered in this website. To find out how much you have learned about Insulin Therapy, take our self assessment quiz when you have completed this section.  The quiz is multiple choice. Please choose the single best answer to each question. At the end of the quiz, your score will display. If your score is over 70% correct, you are doing very well. If your score is less than 70%, you can return to this section and review the information.

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