Bodybuilding is an extreme sport in which higher level competitors often go to great lengths to excel.
While some prefer to stick to natural methods of building muscle, others turn to pharmaceuticals such as anabolic androgenic steroids and insulin.
Though people traditionally use insulin only in medical contexts for diabetes, bodybuilders often exploit it for muscle-building purposes. They use it to cause muscles to absorb nutrients quickly after a workout.
This comes with significant risks.
This article details how some people use insulin in bodybuilding and describes its effects and potentially serious side effects.




What is insulin?


Insulin is a peptide hormone produced in the cells of your pancreas, which is an organ located in your abdomen just below your liver (1Trusted Source, 2Trusted Source).
Insulin’s primary function in your body is to cause your cells to take up and store sugar (glucose) from your blood. It also encourages cells to take in amino acids (proteins) and lipids (fats) to a certain extent (1Trusted Source, 2Trusted Source).
Insulin also prevents the breakdown of glycogen, protein, and fat in your body. Glycogen is a form of stored carbohydrates in your tissues (3Trusted Source).
Your body releases it mainly in response to increases in blood sugar after you’ve consumed carbs.
In a person who doesn’t have diabetes, insulin levels rise after a meal and gradually decrease until the next meal. However, in people with diabetes, the body doesn’t produce enough insulin.
Traditional use

Pharmaceutical insulin is most often used in people with diabetes, a condition in which the body produces little to no insulin (type 1) or becomes resistant to insulin (type 2).
In this case, blood sugars become uncontrolled due to inefficient carbohydrate metabolism. This may cause harm to several organs in the body (4Trusted Source).
Medical professionals often prescribe insulin or other medications to help lower high blood sugar and get it back within the desired range.
A healthy range of blood sugar levels is 80–130 mg/dl before eating and 180 mg/dl or under within 1–2 hours of a meal, according to the American Diabetes Association (ADA) (5).
When people use insulin, it’s usually because they have diabetes and require insulin to help manage their blood glucose levels.
SUMMARYInsulin is a hormone produced in the body that promotes blood sugar storage. Some people with diabetes use supplemental insulin when their bodies don’t produce enough.

Main types of insulin


While pharmaceutical insulin is often lumped into one category, it’s important to distinguish between the different types available on the market.
Short-acting

Short-acting insulins have a quick onset time of about 5–30 minutes after you administer them, with a peak effect in 1–3 hours. They remain active for 2–8 hours (1Trusted Source).
This is the type of insulin almost exclusively used in bodybuilding circles. The goal is to encourage muscles to absorb nutrients quickly after a workout.
Intermediate- and long-acting

Intermediate-acting insulins have a longer onset at 2 hours or more and a duration of action of 12–24 hours, depending on the specific type (1Trusted Source).
People using insulin for bodybuilding don’t typically use these types of insulin because of their slower onset and extended effect time.
Biphasic

This type, also called premixed insulin, contains a blend of long-acting and short-acting insulin for more precise blood sugar control in certain people with diabetes (1Trusted Source).
Biphasic insulins are generally used only for medical purposes. Bodybuilders don’t typically use them.
SUMMARYWhile several types of insulin exist, bodybuilders almost exclusively use short-acting varieties because of their quick onset and short duration of action.


Uses of insulin for bodybuilding


Though people typically use insulin to manage their blood sugar, high level bodybuilders often use it for off-label purposes, including to promote muscle gains.
Off-label purposes are those that aren’t officially listed on the product label or recommended by healthcare professionals.
Why do bodybuilders use it?

Anabolism, the metabolic process of building up, is essential to packing on muscle. Bodybuilders often try to maximize this process.
Considering that it promotes nutrient storage and helps prevent cell breakdown, insulin is considered an anabolic hormone.
This lends it well to bodybuilding, in which the central purpose is to build up muscle mass through strategic diet and exercise.
May support muscle growth

While insulin is best known for its role in controlling blood sugar, it has a few other notable effects that make it desirable for bodybuilders.
One such effect is its ability to help with muscle protein synthesis, the process through which the body builds muscle.
A 2006 study in 19 healthy young adults concluded that, when people received intermediate doses of insulin, they had a boost in muscle protein synthesis and a decrease in muscle protein breakdown (3Trusted Source).
In addition, a 2016 review suggests that insulin has a permissive role in the muscle-building process, as long as you eat enough protein (6Trusted Source).
This means insulin allows muscle building to take place, even though it doesn’t seem to directly promote it.
It’s important to note that sufficient amino acids, the building blocks of protein, must be present in order to promote muscle gains in the presence of insulin (7Trusted Source).
Often combined with other drugs

Another important factor to consider is the pairing of insulin with other performance-enhancing drugs, such as anabolic androgenic steroids or growth hormone.
While insulin alone may not have a potent effect on muscle protein synthesis, it may have an enhanced effect when paired with anabolic steroids or growth hormone (8Trusted Source).
However, data in this area is limited as a result of ethical restraints in research. Users must tread with extreme caution.
Promotes carbohydrate storage

A well-known effect of insulin is its ability to promote carbohydrate storage.
In the bodybuilding community, people commonly consume carbohydrates after a workout to refuel the exercised muscles by promoting glycogen replenishment.
Glycogen is the stored form of carbohydrates in the body. It’s stored in muscle cells as well as the liver.
Ensuring sufficient glycogen stores helps support the muscle-building process by aiding in protein synthesis (9Trusted Source).
To further enhance nutrient storage and muscle fullness after exercise, high level bodybuilders sometimes use insulin to help shuttle blood glucose and amino acids (protein) into muscle cells (1Trusted Source).
In the enhanced bodybuilding community, people usually take insulin only immediately after a workout to promote an anabolic state.
SUMMARYWhile the vast majority of people who use insulin do so to manage diabetes, some high level bodybuilders use it for off-label purposes, usually to support muscle growth and promote carbohydrate storage.