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.

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Insulin is a peptide hormone produced in the cells of your pancreas, which is an organ located in your abdomen just below your liver (1, 2).

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 (1, 2).

Insulin also prevents the breakdown of glycogen, protein, and fat in your body. Glycogen is a form of stored carbohydrates in your tissues (3).

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 (4).

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.


Insulin 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.

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


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 (1).

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 (1).

People using insulin for bodybuilding don’t typically use these types of insulin because of their slower onset and extended effect time.


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 (1).

Biphasic insulins are generally used only for medical purposes. Bodybuilders don’t typically use them.


While several types of insulin exist, bodybuilders almost exclusively use short-acting varieties because of their quick onset and short duration of action.

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 (3).

In addition, a 2016 review suggests that insulin has a permissive role in the muscle-building process, as long as you eat enough protein (6).

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 (7).

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 (8).

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 (9).

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 (1).

In the enhanced bodybuilding community, people usually take insulin only immediately after a workout to promote an anabolic state.


While 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.

While insulin is a hormone produced in the body, injecting it comes with some serious potential dangers. For most people, it’s not worth the risk.

Low blood sugar

The main potential complication of using insulin is experiencing low blood sugar, also known as hypoglycemia.

While people with diabetes often use insulin to help manage blood sugar, people without diabetes produce sufficient amounts from cells in the pancreas.

Therefore, if you’re using supplemental insulin in an attempt to enhance muscle gains, you run the risk of having too much insulin in your bloodstream, which could send your blood glucose levels too low.

Common symptoms of hypoglycemia include (10):

  • drowsiness
  • fatigue
  • hunger
  • irritability
  • paleness
  • shakiness

If you experience any of these symptoms, eat or drink a carbohydrate-containing food or beverage immediately to help bring your blood sugar back up.

In more severe cases, hypoglycemia may result in confusion, blurred vision, seizures, loss of consciousness, or a combination of these. It may even lead to death (10).

This side effect alone is enough to make off-label insulin unsafe for most bodybuilders. Thus, we strongly discourage its use for bodybuilding.

A bump or dimple at injection site

Another potential side effect of using insulin is acquiring a small bump or dent at the injection site after repeated injections in the same spot. It usually occurs in the belly area and is also known as lipodystrophy (11).

This is due to the effect insulin has on fat cells in this area, causing them to change shape slightly. It is not harmful.

Insulin users may want to alternate injection sites to help prevent this effect.


The use of insulin for off-label purposes comes with some serious risks, most notably hypoglycemia. Think critically about this if you’re considering using insulin for bodybuilding.

Before deciding to use insulin, it’s extremely important to weigh the pros and cons.

Numerous bodybuilders have died from insulin abuse. Thus, proper education and guidance are key.

It’s also important to be aware of the legal ramifications in your country of using insulin for nonmedical purposes. In some countries, insulin is available for purchase over the counter, while other countries regulate its distribution tightly.

In addition, many sporting federations consider insulin a banned substance unless it’s used for diabetes management.

Carbohydrate intake

The most important aspect of insulin use, especially in the bodybuilding population, is carbohydrate intake.

If you’re using insulin to build your physique, a general rule for adults is to consume at least 10–15 grams of easily digestible carbs for every IU (international unit) of insulin you administer (12).

The amount of carbs you consume directly affects your blood glucose levels. Thus, if your carb intake is too low when you’re taking insulin, there is a high risk of hypoglycemia.

To accurately track blood sugar levels, a glucose meter, or “glucometer,” is an essential tool to have. You can buy one at most pharmacies.

Never use before sleeping

You should never administer insulin before you go to sleep. This is very dangerous and could result in a coma or even death.

This is because, while asleep, you wouldn’t be able to detect the early stages of hypoglycemia, should it occur.

Therefore, if you choose to use insulin, administer it only during waking hours when you can compensate for a drop in blood sugar by consuming carbs.


We strongly discourage using insulin in bodybuilding. Should you choose to use it, proper education and guidance are key.

Insulin is an anabolic hormone produced in the pancreas that is essential for blood sugar control.

People with diabetes whose bodies don’t produce enough insulin often use supplemental insulin to compensate for this.

High level bodybuilders also commonly use insulin for off-label purposes because it may support muscle gains and promote carbohydrate storage.

Insulin use comes with some serious health risks, most notably low blood sugar. Therefore, we strongly discourage its use for bodybuilding unless you’re using it under the supervision and guidance of a healthcare professional.

Should you choose to use insulin for bodybuilding, proper education and guidance are essential in avoiding potentially serious health outcomes, including death.