Table of Contents
What is insulin, and what are its main functions?
Insulin is a hormone secreted by our pancreas. The pancreas is an organ located behind the stomach. There are clusters of cells in the pancreas called “islets”, which produce insulin in the necessary amounts. (Felman, 2018)
There are several functions of insulin in the body:
- Controls the amount of glucose in the body
- Helps store glucose in the liver, fat, and muscles
- Regulates the body’s metabolism of carbohydrates, fats, and proteins
(Jaffe & Hess-Fisch, 2021)
To fully understand the connection between insulin and glucose, and the roles they play, let us look further into what glucose is.
What is glucose and what is its role in the body?
Glucose is a basic type of sugar which is part of the food we eat, a fundamental building block of the carbohydrates we consume.
Glucose primarily functions as a biological fuel source for the body. While all cells in our bodies possess the ability to utilize glucose to generate energy, there are specific cells that rely solely on glucose to be able to produce the energy to function optimally. Some of these cells are our brain and nerve cells, mature red blood cells, the cells of the lens of the eye, some retinal cells, and cells of the innermost portion of the kidneys. (Robbins, 2017)
Evidently, glucose is vital for the healthy functioning of our bodies.
What is the connection between insulin and glucose?
Once consumed, food is broken down into glucose in our stomachs. The stomach and small intestines then absorb the glucose and release it into the bloodstream. Once in the bloodstream, the glucose will either enter cells to be used to produce energy or will be stored for later use.
And here is when insulin comes into play.
Insulin is necessary for glucose to enter cells where it can be converted into energy. In very simple terms, insulin is like a key which can unlock cell doors for glucose to enter.
Insulin also helps our bodies store extra glucose for later use. Insulin can covert the extra food into larger packages of glucose called glycogen.
The pancreas is very sensitive to the amount of glucose circulating in the bloodstream at any given time. It produces and releases just enough insulin to work on the amount of glucose in the bloodstream. Based on our food intake, blood glucose levels fluctuate, and in turn so does insulin levels.
If for some reason, the pancreas is unable to produce sufficient insulin, or if our cells aren’t receptive of insulin, then the glucose will have no place to go and will remain in the bloodstream. If this condition persists or if a person is born with it, then it inevitably leads to diabetes and a range of other health conditions.
(Kaiser Permanente, 2019)
What happens to the body when there isn’t enough effective insulin?
There are two ways insulin can lose its effectiveness in the body.
- When the pancreas is unable to produce enough amounts of insulin – (type 1 diabetes)
- When the cells are no longer sensitive to the insulin produced by the body (insulin resistance) (type 2 diabetes)
Let’s understand exactly how these conditions affect the normal functions of the body.
When either of the two conditions mentioned above develop in the body, the following changes occur:
- Glucose can no longer enter the cells and therefore there is an accumulation of glucose in the blood, which leads to hyperglycemia (high blood sugar), which is essentially diabetes.
- When blood sugar levels hit high levels (around 180mg/dL) the kidneys detect this and try to rectify the abnormality by expelling glucose in urine. This makes the individual constantly thirsty due to frequent urination. Further, this condition causes dehydration.
- Not having enough glucose in the cells means the cells can no longer produce enough energy and are therefore starved, leading to lethargy and loss of weight. Individuals tend to feel hungry all the time, as well.
- Over time, hyperglycemia can harm the nerves and small blood vessels in your eyes, kidneys, and heart. It can also lead to hardening of the arteries (atherosclerosis), which increases the risk of heart attacks and strokes.
- The cells resort to breaking down body fat instead when there is not enough glucose to convert into energy. But metabolic process of breaking down body fat results in a byproduct called ketones. High levels of ketones lead to a very dangerous condition called “diabetic ketoacidosis” (DKA), which can turn lethal very fast if not treated quickly.
(WebMD, 2019)
Before delving further into the practicalities of using insulin as a medication to treat diabetes, let us look at what diabetes is.
What is diabetes?
Diabetes is a metabolic disease that results in high blood sugar levels.
It was once called a “diseases of affluence”, but now it is a disease prevalent among the poor and affluent alike. Diabetes is prevalent in developing countries, especially in Asia, where high prevalence of smoking and heavy alcohol use, high intake of refined carbohydrates and decreased physical activity levels has led to this disease running rampant among all classes of people. (Hu, 2011)
According to the International Diabetes Federation (IDF), 463 million people around the world live with diabetes, with a further 1.1 million children and adolescents under the age of 20 living with type 1 diabetes. The numbers are predicted to get higher in the future. (International Diabetes Federation, 2019)
Diabetes is further classified as Type 1 diabetes and Type 2 diabetes.
Type 1 diabetes
Type 1 diabetes is considered an autoimmune disease, which means that the body starts attacking its own cells. In this case the body attacks insulin producing cells and thus rendering the body unable to produce insulin. This can happen over a period of a few weeks, months, or years.
Over time, the pancreas will stop making insulin, or will be unable to produce enough insulin, which will result on the individual having to resort to using exogenous insulin in the form of injections.
Type 1 diabetes is most often identified in children but can also occur in adults. Also, the diagnosis of type 1 diabetes likely to take place in adulthood.
Type 2 diabetes
Type 2 diabetes is where the individuals develop insulin resistance. With this development the body becomes unable to use insulin properly. At first, the pancreas will try to make up for it by producing extra insulin. But the pancreas will not be able to keep it up and over time will be unable to make enough insulin to control blood sugar levels.
Type 2 diabetes can be manageable through a healthy diet and exercise, to a certain extent. However, individuals may need oral medications and/or insulin to help regulate blood sugar levels.
(American Diabetes Association, 2021)
When it comes to the management of type 1 and type 2 diabetes, one major difference is that for type 1 diabetes the use of insulin is a must, while for type 2 diabetes it is possible to develop an individualized blood sugar management program consisting of a healthy diet, exercise and pills. But still, insulin may have to be taken later for individuals with type 2 diabetes, as the disease progresses especially for individuals who’ve had diabetes for over 10 years. (Gray, 2020)
What are the types of insulin available?
| Type of Insulin | Usage | Onset | Peak (maximum effectiveness) | Duration of Effectiveness | Indication |
| Rapid-acting insulin (bolus insulin replacement) | To correct high blood sugar | Begins working about 15 minutes after injection | Peaks between 1 to 3 hours | Effects last between 3 and 4 hours | Before a meal |
| Short – acting insulin | 30 to 60 minutes after injection | Within 2 – 3 hours | Lasts 5 to 8 hours | 30 minutes before a meal | |
| Intermediate -acting insulin (basal or background insulin replacement) | To maintain a low and steady level of insulin throughout the day. | 1 to 2 hours after injection | Between 4 to 12 hours | Lasts 14 to 16 hours | |
| Long – acting insulin (basal or background insulin replacement) | To maintain a steady level of insulin throughout the day | 2 hours after injection | No pronounced peak. Works like typical pancreatic insulin | Lasts 24 hours or longer |
(Higuera, 2019)
(Jaffe & Hess-Fisch, 2021)
(Gray, 2020)
The above is merely a general idea of the types of insulin available. The exact usage, onset, peak, duration, and indication will differ according to the specific medication prescribed by your doctor. A combination of insulin between rapid/short -acting insulin with intermediate/long – acting insulin is commonly used.
How is insulin administered?
Currently, insulin is only available through injection, insulin pumps, or inhalation. The most common methods of delivery of insulin are through injection and insulin pumps. Insulin doesn’t come in pill form because if taken as a pill, the digestive system would break down the insulin before it could take effect on the body. (Mayo Clinic Staff, 2021)
Insulin Pumps
Insulin pumps are little, computerized devices that function very similarly to the human pancreas. They deliver insulin into the body in two ways:
- Continuous small doses of short acting insulin (basal) – your doctor will help you set up the basal insulin rate in your device. Multiple basal settings can be programmed into your pump.
- Variable amounts of insulin before a meal is eaten (bolus) – You will be able to define and program the amount of bolus insulin you will need before a meal. And most pumps come equipped with bolus calculators that can help you figure out how much insulin you will need depending on your blood glucose levels and the amount of carbohydrates you will be consuming
How an insulin pump works
Traditional insulin pumps contain three main parts: the pump, tubing, and the infusion set.
The insulin pump contains an insulin reservoir, where the insulin is stored, ready to be pumped into the body according to how its programmed.
The tubing is at thin plastic tube (catheter) which is connected to the to the insulin reservoir in the pump. The tubing can come in several lengths, depending on the need.
The infusion set consists of a short, thin tube (cannula) and an adhesive patch that can attach to your skin. The cannula initially has a small needle inside that will help in puncturing the skin to make it possible for the cannula to be inserted into the skin. The needle must be removed after the cannula is inserted and the cannula will remain under the skin and is the means through which insulin is delivered into the body. The infusion set is usually implanted around the stomach area, but it can also be placed on the thigh, hips, upper arms, or buttocks.
Insulin pumps available in the market now come with all kinds of customizable features, making it easier and easier to use. One major feature is when the insulin pump is integrated with a continuous glucose monitoring sensor, which goes a long way when it comes to insulin and diabetes management.
(Aleppo, 2019)
Insulin injections
Injecting insulin can be achieved with a vial of insulin and a syringe or with an insulin pen. Insulin is injected subcutaneously, or just below the skin.
Insulin Pens
The use of insulin pens is recommended for individuals with bad eyesight or those with limited dexterity like the elderly and children, as it is a less complicated process to use them as opposed to the use of a vial and syringe, which requires a two-step process. Insulin pens also tend to cause less pain than a syringe.
When injecting with an insulin pen, it is important to inject straight into the skin. It is also vital to hold the pen in place for a few seconds after delivering the insulin to make sure than no insulin leaks out.
Using a Vial and Syringe to Inject Insulin
These are a few things to consider when using insulin injections:
- Needle length – shorter needles that are about 4mm long is recommended, although for heavier individuals, they might have to resort to using longer needles.
- Needle gauge – a short, thin needle is the most suitable
- Shorter and thinner needles cause minimal pain as well. Your health care provider will help you determine the needle length and gauge most suited for your body type.
- When using short needles, you should normally be able to insert the needle at a 90-degree angle, but slimmer individuals may have to pinch up their skin to inject. When using longer needles, injecting at a 45-degree angle will be necessary.
- Always remember to leave the needle in the skin for about 10 seconds after injecting, to make sure there is proper delivery of the insulin
- Always practice safe ways of disposing needles after using
- Always be careful when drawing out insulin from the vial. Ensure that the dosage is right.
Factors to Consider When Injecting Insulin into Different Areas of the Body
When injecting insulin daily into the skin, it is vital to rotate the site of injection to avoid thickening of the skin due to constant insulin exposure. There are several areas in the body that can be used as injection sites.
- Stomach – Avoid injecting around the belly button area or on scars on the abdomen by at least two inches. This area has the quickest absorption rate.
- Thigh – Measure out at least 4 inches (a hand’s width) from above the knee and 4 inches (a hand’s width) from the top of the leg when choosing a site for injection on the thigh. The top and outer areas of the thigh are the optimal sites. Refrain from injecting into the inner thigh of the legs because of the high number of blood vessels and nerve ending in the area. This area has one of the slowest absorption rates
- Arm – The best areas in the arm for injection are located in the fatty tissue in the back of the arm, between the shoulder and elbow
- Buttock – The ideal area is in the hip or “wallet area” and not in the lower buttock area
- When rotating injections within the same body part, always keep away from a previously used injection site by at least an inch (two finger widths). This area also has one of the slowest absorption rates.
- Avoid injecting into scar tissue or areas with varicose vein, as these sites may interfere with the absorption of insulin
- Keep in mind that massages or exercise that might occur immediately after injection will speed up absorption because of the increase in circulation in the injection site.
(Sloane, 2021)
Diabetes, once a debilitating, life altering disease with many complications, is now a highly manageable disease, thanks to the tremendous advances in modern medicine. With the abundance of resources and help readily available, the limitations of living with diabetes have been brought down to a minimum. And further advances in medical technology will only further minimize the effects of this metabolic disease.
References
Aleppo, G. (2019, March 03). Insulin Pump Overview. Retrieved from endocrineweb: https://www.endocrineweb.com/guides/insulin/insulin-pump-overview
American Diabetes Association. (2021). Blood Sugar and Insulin at Work. Retrieved from American Diabetes Association: https://www.diabetes.org/diabetes-risk/prevention/high-blood-sugar
Felman, A. (2018, November 21). An overview of insulin. Retrieved from Medical News Today: https://www.medicalnewstoday.com/articles/323760
Gray, H. (2020, Decemebr 14). What Are the Pros and Cons of Switching to Insulin for Type 2 Diabetes? Retrieved from healthline: https://www.healthline.com/health/type-2-diabetes/insulin-switch-pros-cons
Higuera, V. (2019, May 07). Everything You Need to Know About Insulin. Retrieved from healthline: https://www.healthline.com/health/type-2-diabetes/insulin
Hu, F. B. (2011). Globalization of Diabetes: The role of diet, lifestyle, and genes. Diabetes Care, 1249 – 1257.
International Diabetes Federation. (2019). IDF Diabetes Atlas 9th edition 2019. Retrieved from Worldwide toll of diabetes: https://www.diabetesatlas.org/en/sections/worldwide-toll-of-diabetes.html
Jaffe, L., & Hess-Fisch, A. (2021). What Is Insulin. Retrieved from Endocrineweb.
Kaiser Permanente. (2019, March 01). How our bodies turn food into energy. Retrieved from Kaiser Permanente: https://cutt.ly/qkjGWqm
Mayo Clinic Staff. (2021). Diabetes treatment: Using insulin to manage blood sugar. Retrieved from Mayo Clinic: https://www.mayoclinic.org/diseases-conditions/diabetes/in-depth/diabetes-treatment/art-20044084
Robbins, C. (2017, October 20). What is the Main Function of Glucose? Retrieved from Livestrong: https://www.livestrong.com/article/201765-what-is-the-main-function-of-glucose/
Sloane, S. B. (2021). Insulin Injections for Diabetes 101: How to Use Insulin? Retrieved from Dario Health: https://mydario.com/how-to-take-insulin/
WebMD. (2019, November 25). What does insulin do? Retrieved from WebMD: https://www.webmd.com/diabetes/qa/what-happens-when-theres-lack-of-insulin