What is insulin?

What is insulin?

Insulin is a hormone responsible for allowing glucose to reach cells in the blood, giving them the energy to work. A lack of effective insulin plays a decisive role in diabetes production.

Hormones are chemical messengers which instruct certain cells or tissues to act in a way that supports a specific body function.

Insulin is essential for staying alive.

In this article we look at how the body produces insulin and what happens when not enough of it circulates, as well as the different types of insulin supplements that a person can use.

What is insulin?

Bottles of Insulin
Insulin is an essential hormone for controlling blood sugar and energy absorption.

Insulin is a chemical messenger that lets cells consume blood glucose, a sugar.

The pancreas is an organ behind the stomach which is the body’s principal source of insulin. Clusters of pancreatic cells called islets contain the hormone and determine the amount of blood glucose in the body based on the levels.

The higher the glucose levels, the more insulin goes into production to control blood sugar levels.

Insulin also helps break down energy-efficient fats or proteins.

A delicate insulin balance controls the sugar in the blood and many processes within the body. If the insulin concentration is too low or high, overly high or low blood sugar may begin to cause symptoms. If there appears to be a low or high blood sugar level, serious health issues can begin to develop.

Insulin problems

The immune system is targeting the islets in some people, and they either stop producing insulin or don’t produce enough.

When this happens, blood glucose remains in the blood, and cells can not absorb it to turn sugars into energy.

This is the beginning of type 1 diabetes and a person with this diabetes variant will need to have regular insulin shots to survive.

In some people, particularly those who are overweight, obese, or inactive, insulin is not effective for transporting glucose into the cells and being unable to carry out its actions. Insulin’s failure to exert its effect on tissues is known as insulin resistance.

Type 2 diabetes can evolve if insulin resistance can not be overcome by the islets.

Doctors have been able to isolate insulin since the early 20th century, delivering it in an injectable form to substitute the hormone for people who are unable to produce it themselves or have elevated insulin resistance.

Types of insulin

A person can take different types of insulin based on how long they need the effects of the supplementary hormone to last.

People categorize these types based on several different factors:

  • speed of onset, or how quickly a person taking insulin can expect the effects to start.
  • peak, or the speed at which the insulin reaches its greatest impact
  • duration, or the time it takes for the insulin to wear off
  • concentration, which in the United States is 100 units per milliliter (U100)
  • the route of delivery, or whether the insulin requires injection under the skin,into a vein, or into the lungs by inhalation.

Persons more commonly inject insulin into the subcutaneous tissue, or the fatty tissue below the skin surface.

Fast-acting insulin

The body absorbs this kind extremely quickly from the subcutaneous tissue into the bloodstream.

People use fast-acting insulin to correct hyperglycemia, or high blood sugar, as well as to regulate spikes in blood sugar after meals.

This form covers:

  • Rapid-acting insulin analogs: These take between 5 and 15 minutes to have an effect. However, the size of the dose impacts the duration of the effect. Assuming that rapid-acting insulin analogs last for 4 hours is a safe general rule.
  • Regular human insulin: The onset of regular human insulin is between 30 minutes and an hour, and its effects on blood sugar last around 8 hours. A larger dose speeds up the onset but also delay the peak effect of regular human insulin.

Intermediate-acting insulin

This form enters the bloodstream at a slower rate but has an advantage of a longer longevity. Managing blood sugar overnight, as well as between meals, is the most effective approach.

Intermediate-acting insulin choices shall include:

  • NPH human insulin: This takes between 1 and 2 hours to onset, and reaches its peak within 4 to 6 hours. It can last over 12 hours in some cases. A very small dose will bring forward the peak effect, and a high dose will increase the time NPH takes to reach its peak and the overall duration of its effect.
  • Pre-mixed insulin: This is a mixture of NPH with a fast-acting insulin, and its effects are a combination of the intermediate- and rapid-acting insulins.

Long-acting insulin

Although long-acting insulin enters the bloodstream gradually, and has a relatively low peak, it has a stabilizing “plateau” effect on blood sugar that can last most of the day.

It’s good for nights, between meals, and at fasts.

The only form available is long-acting insulin analogs, and these have an onset of between 1.5 and 2 hours. While different brands have different durations, overall they range from 12 to 24 hours.


Insulin is a critical hormone that regulates how cells and tissues consume energy, and how fat and protein breakdowns.

This hormone is secreted by clusters of cells within the pancreas called islets. Insulin resistance increases as cells in the body respond less to its instructions.

The immune system is targeting the islets in some individuals, stopping the development of insulin and contributing to type 1 diabetes. Type 2 diabetes occurs when insulin resistance coexists with insulin production being deficient in compensatory increases.

People may take shots of insulin to counteract the impacts of insulin resistance. A person would take short, moderate, and long-acting insulins depending on how quickly they need to see a drop in blood sugar and the length of time a person needs to control blood sugar.


Does every person with diabetes need to take insulin?


No. Insulin is mandatory for people with type 1 diabetes, but many people with type 2 diabetes can manage blood sugar levels with diet, exercise, and oral medications. individuals with type 2 diabetes may also need insulin for control. Maria Prelipcean, MD

Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.


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