If you’re a nurse who’s worked in direct patient care, it’s likely you’ve administered insulin at some point in your career. Have you ever wondered how insulin works?
Insulin Basic Review
Before we dive into the mechanics of insulin, let’s review some basics first. Insulin is a substance that is normally secreted by the beta cells of the pancreas to help the body use or store glucose. For individuals with type 1 diabetes mellitus, the beta cells are destroyed, thus they require an external source of insulin to help their bodies process glucose. Individuals with type 2 diabetes continue to make insulin, however their bodies don’t respond well to it. They need diabetes oral medication or a form of insulin to help regulate blood sugar levels.
Injectable insulin is manufactured through recombinant DNA technology and can be categorized based on onset, peak, and duration of effect (i.e. rapid-, short-, intermediate-, long-, and ultra long-acting). It is dissolved or suspended in liquid and the standard strength in the U.S. is U-100, meaning it has 100 units of insulin per mililiter of fluid. U-500 is also available for patients who are extremely insulin resistant. (American Diabetes Association, ND). It is typically injected subcutaneously into the adipose tissue and absorbed into the blood.
Inhaled insulin became available in 2015 and is a rapid-acting formulation that should be taken at the beginning of each meal. It can be used by individuals with type 1 or type 2 diabetes. Note that inhaled insulin must be administered with injectable long-acting insulin in patients that require extended insulin coverage.
Mechanism of Action of Insulin (Facts and Comparisons, 2019)
How does insulin work? When carbohydrates are eaten, the body breaks them down into glucose – a simple sugar and the body’s main source of energy. When blood glucose levels rise, the pancreas releases insulin, which helps glucose enter the cells. Insulin is secreted into the bloodstream and binds to the receptors on the surface of the target cell membrne. As insulin and its receptor move into the cell, this activates glucose transporter channels to move to the surface of the cell, allowing glucose to enter and be used for metabolism (Perkins, 2017).
The specific target cells are located in the liver, skeletal muscle, and adipose tissue. Within the liver, insulin stimulates glycogen synthesis of fatty acids, which are released into the circulation as lipoproteins. In the skeletal muscles, insulin increases protein and glycogen synthesis. And in adipose tissue, insulin helps to process circulating lipoproteins and assists in triglyceride synthesis and storage by adipocytes. In addition, insulin stimulates cellular uptake of amino acids and increases cellular permeability to ions such as potassium, magnesium, and phosphate (Facts and Comparisons, 2019).
Types of Insulin (Perkins, 2017; American Diabetes Association, ND)
There are over 20 different types of insulin used today categorized by how they are manufactured, what they do in the body, and their cost. They are prescribed based on onset, peak, and duration.
| Types of Insulin |
| Type |
Onset
(Time insulin begins to work) |
Peak
(Time insulin is at maximum strength) |
Duration
(How long insulin continues to lower blood glucose) |
Examples |
| Rapid-acting |
15 minutes |
1 hour |
2 to 4 hours |
Insulin glulisine
Insulin lispro
Insulin aspart |
| Inhaled insulin |
12 to 15 minutes |
30 minutes |
180 mintues |
Technosphere insulin – inhalation system |
| Regular or Short-acting |
30 minutes |
2 to 3 hours |
3 to 6 hours |
Human regular |
| Intermediate-acting |
2 to 4 hours |
4 to 12 hours |
12 to 18 hours |
Insulin NPH |
| Long-acting |
Several hours after injection |
Does not peak |
Continues to work up to 24 hours |
Insulin detemir
Insulin glargine
Insulin degludec |
| Ultra long-acting |
6 hours |
Does not peak |
Lasts 36 hours or longer |
Glargine U-300 |
Nursing Considerations for Insulin Administration (Lippincott Solutions, 2022; Perkins, 2017)
- Rotate injection sites (arms, abdomen, thighs, and buttocks) and locations within the same site to prevent tissue injury.
- Ensure the type of insulin, unit dose, and syringe are correct.
- When combining insulins in a syringe, ensure they’re compatible.
- Rapid- or short-acting insulin is clear
- Intermediate-acting insulin is cloudy
- Draw up the clear insulin first to prevent contamination of the rapid insulin with intermediate-acting insulin; remember “clear to cloudy.”
- Prior to drawing up insulin, roll and invert the bottle gently; do not shake.
- Insulin is commonly administered with a syringe and can also be given by insulin pen and pumps. Fast-acting insulin may be administered intramuscularly or intravenously in emergency situations (Perkins, 2017).
- Monitor patients closely for signs of hypoglycemia and hyperglycemia.
For complete information, please consult the drug’s specific package insert or the
Nursing2022 Drug Handbook® + Drug Updates.
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