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Insulin: Its Primary Function and More

If you’re someone suffering from diabetes then the term insulin might be quite familiar to you. Being diagnosed with diabetes is not an easy situation to cope with. Insulin is the hormone that can single-handedly change your life for the better or worse.

Let me simplify it for you. Insulin is one of the most important hormones produced in the human body. It is responsible for several metabolic processes mainly involving glucose metabolism. If not produced in the right amount, it can lead to lifelong diseases like Type-1 or Type-2 diabetes.

On, the other too much insulin can lead to various medical conditions. All this talk about insulin and diabetes might make you wonder, What is the primary function of insulin? How does it really work? Well, in this article we will be discussing just that and much more. 

Table of Content

What is Insulin?

Insulin is a hormone that is responsible for glucose metabolism. The source of this glucose can be either carbohydrates, protein, or fats. It helps in the absorption of glucose by the cells of your body, allowing them to have sufficient energy to carry out their specific functions.

There are different types of hormones in the body. Insulin is a protein hormone a.k.a peptide hormone. Its structure consists of chains of amino acids which in turn form peptides. Human insulin contains 51 amino acids.


However, you’d be surprised to know that pig and cow insulins were initially used to produce synthetic insulin as their insulin structure was closest to the human insulin structure. This is the insulin that is available in the market in the form of injectable drugs.

Insulin is mainly produced in the pancreas by a group of glands called the Islets of Langerhans. The pancreas also secretes the hormone glucagon. Both these hormones are responsible for maintaining a stable glucose concentration in your blood.

However, if you have decreased production of insulin or the absence of insulin altogether, then you might develop diabetes mellitus. Depending on the type of diabetes you have, you might be suggested to inject insulin to make up for the decreased amount produced. 

Types of Insulin

Insulin is a single particular hormone produced in the body. Naturally produced insulin is structured in the same way. However, synthetically produced insulin has different formulations which cater to the type of diabetes and the condition of the patient.

Insulin is mainly categorized according to their onset of action, peak time meaning how long does it take to exert its maximum therapeutic effect, duration of action, route of administration i.e if they are administered subcutaneously or intravenously, concentration, appearance, etc.

Irrespective of their differences, the primary function of insulin is the same. Insulin can be classified as follows:

Rapid-Acting Insulin 

Rapid-acting insulin starts working within 5-15 minutes, it reaches its maximum therapeutic effect within 1- 2 hours. The effects of rapid-acting insulin usually last for 4-5 hours. The peak time and onset of action usually remain the same irrespective of the concentration. 


Some commonly used rapid-acting insulins are:

  • Lispro, available in the market as Humalog, Kwikpen, Admilog.
  • Aspart found with the trade name Novolog, FlexPen, Fiasp.
  • Glulisine, available in the market as Apidra, Apidra Solostar pen.
The dose of the rapid-acting insulin determines the duration of the action.

Intermediate-Acting Insulin

It is a type of insulin with long-lasting effects. The insulin is designed to enter the blood circulation slowly as a result its effects are expressed later on. It is suitable for use at night time, after meals, or while fasting.


Intermediate-acting insulin contains the following types of insulin:

  • NPH insulin: Neutral Protamine Hagedorn insulin, aka isophane insulin is usually administered subcutaneously. It’s usually used once or twice a day. It takes about 1 to 2 hours to exert its effects. The duration of action lasts for about a day or so.
  • Pre-mixed insulin: Premixed insulin is a type of insulin where regular human insulin or rapid-acting insulin is mixed with NPH insulin. The effects are an amalgamation of both types.

Long-Acting Insulin

Long-acting insulin analogs take quite a bit of time to reach blood circulation. However, its effects are way more long-lasting. They don’t have a high peak, but they for a plateau concentration in the blood which is ideal for diabetic patients who are fasting.

It can also be used after meals and right before sleeping. Their onset of action is between 1 and a half to 2 hours. But, their duration of action varies according to the brand of insulin used. The duration varies from 12 to 24 hours.


The long-acting insulins available in the market are as follows:

  • Insulin Glargine, available as Lantus, Tuojeo, Basalgar, etc.
  • Insulin Detemir, available as Levemir.
  • Insulin Degludec, available as Tresiba.

How Does Insulin Work?

Insulin is a hormone that participates in glucose metabolism and maintains blood sugar levels. Metabolism is the process by which food products are broken down and absorbed in the form of energy.

As discussed before, insulin is produced in the pancreas and secreted in the bloodstream. The food that we eat especially carbohydrates is broken down into glucose. This glucose is a type of sugar. It is a form of monosaccharide which is the simplest form of sugar.

Glucose is responsible for making your blood sugar levels rise. The rise in blood sugar levels is detected by the pancreas with the help of a group of cells called Beta cells. The beta cells detect the rise and fall of blood glucose levels by the number of products of glucose catabolism.


The beta-cell has distinctive proteins known as glucose transporter 2 and glucokinase which help in the catabolism process. The insulin promoters in the cell finally stimulate the insulin secretion process.

After secretion, insulin helps the glucose to enter into the cells. A portion of this glucose is used up as energy. The remaining portion is stored as glycogen in the body in different sites such as the liver, muscles, fat cells, etc.

On the contrary, if you have a low blood sugar level then the pancreas releases another hormone, namely Glucagon. Glucagon is responsible for breaking down the stored glucose in the body and bringing glucose back to the bloodstream to maintain blood sugar levels.

Does Insulin Increase Blood Glucose?

Insulin is the hormone that is responsible for breaking down glucose and turning it into energy. It helps glucose to enter into cells. Thus, it maintains a normal blood sugar level when there is a surge of glucose in the blood after having food.

So, instead of letting the blood sugar level rise, Insulin actually decreases the blood sugar level. However, if you are someone who is suffering from diabetes then an exceptional scenario needs to be considered. You might be someone who has been prescribed to inject insulin.

For some reason, you might accidentally inject less amount of insulin compared to the prescribed dosage. This will lead to raised blood sugar as the small amount of insulin that was administered won’t be able to tackle the surge of glucose.

The hormone that is mainly responsible for increasing blood sugar is Glucagon. It breaks down the glucose storage and brings glucose to the bloodstream resulting in a rise in blood glucose.

What Is the Primary Function of Insulin?

The primary function of insulin is to enable the uptake of glucose by the body tissue. This includes the muscles, fat cells, and liver. This mainly regulates the level of glucose in the blood. After being stimulated by the rising levels of blood glucose, insulin is secreted from the pancreas.

The targeted cells have insulin receptors to which the released insulin attaches. After attachment to the receptors, insulin enables the glucose transporters to translocate to the cell membrane which helps in glucose uptake by the target cell.

Insulin stimulates the uptake of amino acids (molecular basis of protein) and glucose by the muscle tissue. This glucose is used for muscle activity and the amino acids are used for building up muscle protein.

In the liver, Insulin stimulates the process of forming storage glucose aka glycogen. It also prevents the process of glycogenolysis, the process of breaking down glucose to be released into the bloodstream.

It also prevents gluconeogenesis, the formation of new glucose compounds from aminoacids and glycerols. So, the overall function of glucose in the liver is to increase glucose storage and decrease the release of glucose in the blood supply.

In the fat cells or adipose tissues, insulin increases glucose uptake. It also increases the intake of fatty acid resulting in increased esterification and storage of fatty acids in the form of triglycerides.

It also prevents lipolysis, meaning the breakdown of fat storage. This helps to store them for future use during exercising, exertion, or stress.

What Is the Role of Insulin in Diabetes?

Insulin is the hormone that plays the biggest role in diabetes. The impairment or lack of secretion of insulin will lead to the formation of diabetes mellitus. There are two types of diabetes:

  • Insulin Dependent Diabetes Mellitus (IDDM) also known as type-1 diabetes.
  • Non-Insulin Dependent Diabetes Mellitus (NIDDM) is also known as type-2 diabetes.

The role of insulin in both types of diabetes is explained as follows:

Role of Insulin in Type-1 Diabetes

Type-1 diabetes can occur irrespective of age. But, it is most prevalent in children, adolescents, and young adults. Type-1 diabetes is thought to be an autoimmune disorder. An infection or triggering agent can cause the symptoms of type-1 diabetes to flare up.

In type-1 diabetes, the body destroys the beta cells of the pancreas resulting in the remnant beta cells producing little to no insulin. For this reason, people with type-1 diabetes mellitus need to use insulin.

Without insulin, their body will not be able to take up glucose and would suffer from a lack of energy necessary to maintain normal function. As type-1 diabetes patients need insulin, this condition is also named Insulin Dependent Diabetes Mellitus.

Patients are usually put on insulin as soon as they are diagnosed with Type-1 diabetes. It might seem overwhelming at first but, the physician will run a few trials to find the best dosage for you. Regular intake of insulin and a change in lifestyle should help manage type-1 diabetes.


Role of Insulin in Type-2 Diabetes

Type-2 diabetes is a type of diabetes where the body cannot properly use the insulin produced by it. The condition is called insulin resistance. The body produces more insulin to combat the resistance but eventually, the cells fail to use the insulin, which causes high blood glucose.

Middle-aged and older people tend to develop type- 2 diabetes more. But, if a child is suffering from childhood obesity they might also have a chance of developing insulin resistance. Type-2 diabetes is not initially treated with insulin. But as time goes by the need to administer insulin might arise.

Losing weight, exercising, maintaining a healthy diet, active lifestyle is initially recommended to combat type-2 diabetes. In the second stage, there are several medications that can be used to treat the condition. If all of this does not give ideal results then insulin can be considered.

A patient with type-2 diabetes can opt for using insulin because it lowers blood glucose much faster than other medications, it has fewer adverse effects, and it can be quite cheap compared to other medications.

Difference Between Insulin and Glucagon

Insulin and glucagon are two major hormones that are responsible for regulating blood sugar levels. Insulin helps in glucose absorption and storage. On the other hand, glucagon helps in breaking down the storage and increasing blood glucose levels when there is less blood sugar.

The difference between insulin and glucagon can be stated as follows:

Insulin Glucagon
Insulin is produced in the beta cells of islets of Langerhans present in the pancreas.Glucagon is produced in the alpha cells of islets of Langerhans present in the pancreas.
Insulin decreases the blood glucose level.Glucagon increases the blood glucose level.
Insulin secretion is activated when the blood glucose level is high.Glucagon secretion is activated when the blood glucose level is low.
Insulin stimulates the cellular uptake of amino acids and glucose.Glucagon stimulates the breakdown of triglycerides to release fatty acids.
Insulin stimulates the formation of glycogen in the liver.Glucagon stimulates the breakdown of glycogen.
Insulin inhibits gluconeogenesis.Glucagon stimulates the release of glucose from the liver through gluconeogenesis.
Insulin increases the cellular uptake of glucose in the skeletal muscle.Glucagon exerts no effect on skeletal muscle.
Insulin stimulates amino acid uptake.Glucagon exerts no effect on amino acids.
Insulin affects the hypothalamus to reduce hunger.Glucagon has no such effect.
Reduced or no production of insulin causes type-1 and type-2 diabetes mellitus.Glucagon deficiency causes glucagonoma and hypoglycemia.

The Function of Insulin and Glucagon

Both insulin and glucagon are vital for the regulation of proper ranges of blood sugar levels. As discussed above, insulin works by increasing cellular uptake of glucose and stimulating the formation of glucose storage in the form of glycogen.


On the contrary, glucagon is stimulated by low blood sugar. Glucagon stimulates the breakdown of glycogen stored in the liver to readily release glucose in the bloodstream raising the blood sugar levels to normal.

After that insulin again attaches to the insulin receptors of the cells facilitating glucose uptake. Both insulin and glucagon work in a cycle functioning one after another and maintaining optimum blood glucose levels.


What is the most predominant function of insulin?

The most predominant function of insulin is facilitating glucose uptake by cells and stimulating storage of glucose in muscle tissue, adipose cells, and the liver.

Does insulin break down glucose?

Insulin helps the fat cells and muscle tissue store extra glucose that they can use as energy. It helps prevent high sugar levels in the blood. Insulin stimulates the muscle tissue and adipose tissue to stop breaking down glucose to bring the blood sugar levels to normal.

Why do you need insulin?

Insulin is necessary for glucose and amino acid metabolism that is obtained from the food we take. Patients with diabetes need to inject insulin to cope up with the deficiency or lack of insulin production in the body.

Where is insulin produced?

Insulin is produced by the beta cells present in a cluster of glands called islets of Langerhans. These are present in the pancreas. The pancreas is also responsible for releasing glucagon.

How does insulin reduce blood sugar?

Insulin reduces blood sugar by stimulating the glucose uptake by cells and increasing glucose storage in the liver, muscle tissue, and adipose tissue in the form of glycogen. It also prevents gluconeogenesis and lipolysis.

The Bottom Line

The most common question asked by people diagnosed with diabetes is, ‘What is the primary function of insulin?’. It is expected for them to wonder about the workings of insulin as it has become a part of their daily life.

Insulin is a wonderful hormone that helps in regulating blood sugar levels. It partners up with glucagon to maintain an optimum range of blood glucose. Lack of insulin production usually leads to diabetes. It can be combated with a change in lifestyle, oral medications, and injecting insulins.

Hope this article helped with your queries. Check out the website for more articles on insulin and diabetes. Your journey to a wholesome and healthy life starts here!

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