How Do Insulins Work?

Reviewed on 1/10/2022


Insulins are a class of drugs used to treat type 1 (T1DM) and type 2 diabetes mellitus (T2DM). T1DM is a condition caused by an autoimmune reaction that destroys the beta cells of the pancreas because of which the body cannot produce or synthesize insulin needed to manage circulating blood sugar levels and therefore the amount of sugar in the blood cannot be controlled. T2DM is a slowly progressive metabolic disorder caused by a combination of genetic and lifestyle factors that promote chronically elevated blood sugar levels.

Insulin is a peptide hormone produced by the beta cells of the pancreas to help metabolize food and use it for energy throughout the body. After a meal, insulin promotes the uptake of glucose (a type of sugar found in many carbohydrates) from the blood into internal organs and tissues such as the liver, fat cells, and skeletal muscles. It allows the body to use glucose for energy; helps in the storage of glucose in the liver, fat, and muscles; and regulates the body’s metabolism of carbohydrates, fats, and proteins.

In nondiabetic conditions, insulin helps in:

  • Regulating blood sugar levels: after meals, carbohydrates are broken down into glucose (the body’s primary source of energy) which then enters into the bloodstream. In addition, the pancreas produces insulin, allowing glucose to enter the body's cells to provide energy.
  • Storing excess glucose for energy: after eating when insulin levels are high, excess glucose is stored in the liver in the form of glycogen.

The general types of insulin therapy include:

  • Long-acting insulin: in between meals, the liver releases glucose so that there is a continuous supply of energy in the body; this insulin helps the body use the glucose and prevent it from reaching excessively high levels.
  • Intermediate-acting insulin: takes two to four hours to work fully and their effects can last up to 18 hours.
  • Rapid- or short-acting insulin: ideal for preventing blood sugar spikes after meals. They begin to work much faster than long- or intermediate-acting insulins but for a shorter period of time, usually about two to four hours.

Without an adequate supply of insulin to promote absorption of glucose from the bloodstream, blood sugar levels can rise to dangerously high levels and can result in symptoms such as fatigue, headache, blurred vision, and increased thirst. If left untreated, the body starts to break down fat instead of glucose for energy, resulting in the build-up of ketone acids in the blood and a syndrome called ketoacidosis, which is a life-threatening medical emergency. In the long term, elevated blood sugar levels increase the risk of heart attack, stroke (loss of blood flow to part of the brain), and diabetic neuropathy.

Insulins are administered as a solution (liquid) and suspension (liquid with particles that will settle on standing) to be injected subcutaneously (under the skin), a powder to be orally inhaled using a special inhaler, an injectable pen, and prefilled pens.

Insulins work in the following ways:

  • They are man-made products similar to human insulin which replace the insulin made by the body. 
  • They help in the blood sugar (glucose) movement into the cells so that the body can use it for energy.
  • In addition, they prevent the liver from producing more sugar (inhibits hepatic glucose production).


Diabetes is defined best as... See Answer


Insulins are indicated to improve glycemic control in patients with T1DM and T2DM along with a proper diet and exercise.


Some of the common side effects include:

Other rare side effects include:

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.


Generic and brand names of insulins include:


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