Pharmaceutical insulin is a hormone used to treat high blood sugar in people with certain types of diabetes. So, what does it have to do with bodybuilding?
Well, like any sport or physical activity, bodybuilding has its limits, and professional or high-level bodybuilders often resort to extreme methods to build muscle mass and push these limits every time a little bit further.
We've all heard about bodybuilders' use and abuse of anabolic steroids. It's estimated that more than half of male bodybuilders use steroid drugs, like Oxymetholone or Nandrolone regularly, with doses that are sometimes 10 to 100 times the recommended therapeutic dose.
Surprisingly, one in four bodybuilders who takes steroids also takes insulin. The combination of the two is believed to be a potent training stimulant that considerably increases metabolic rate, anabolic metabolism, and, ultimately, muscle growth.
But while using insulin for muscle mass gain makes sense scientifically, it also comes with significant risks and side effects.
So, why do bodybuilders take insulin? How does it work? What are the benefits? What are the risks?
Related article: Does insulin need to be refrigerated, and how to store it properly?
What is insulin?
Insulin is a hormone naturally produced by the body. The pancreas releases it in response to rises in blood sugar levels after carbohydrate consumption or glucagon production.
Pharmaceutical insulin is used for people with diabetes. In this chronic health condition, the body does not produce enough insulin, has no insulin at all (type 1 diabetes), or has become resistant to insulin (type 2 diabetes).
Its primary function is to help move the sugar from the bloodstream into the cells that use it immediately as a source of energy or store it for later use.
How is insulin administered?
Insulin is a liquid water-like medicine that’s administered through subcutaneous injections. It's injected under the skin with tiny, thin needles.
Main insulin injection devices include syringes and vials, insulin pens, and insulin pumps.
Related article: A step-by-step guide to using an insulin pen for injections.
Why do bodybuilders take insulin?
Bodybuilding is the practice of developing one’s muscles through hypertrophic exercises, progressive resistance, and diet. It focuses on optimized muscle growth for aesthetic performances.
A big part of bodybuilding includes diet and supplements. While most bodybuilders stick to more or less natural supplements such as proteins, creatine, caffeine, glutamine, and others, high-level ones often turn to pharmaceutical products such as anabolic, steroids, growth hormones, and insulin for extreme muscle growth. These help the muscles absorb more nutrients quicker after workout sessions.
Here's how insulin can help with bodybuilding (we’ll discuss the risks and side effects below).
Note: The use of insulin for bodybuilding is absolutely off-label. It’s not recommended by healthcare providers and is not part of the list of official uses of this medication.
Related article: How long do insulin vials last, and how many do you need per month?
Insulin and muscle growth
Besides its traditional blood sugar control use, insulin is an anabolic hormone known to support muscle growth. While science backs up the fact that insulin promotes muscle growth, the mechanisms in which it works are still debated. Here are the main leads:
- Insulin stimulates muscle protein synthesis and decreases muscle protein breakdown. Muscle protein synthesis is the process of building muscle mass from amino acids (the building blocks of proteins).
- Insulin promotes carbohydrate storage in the muscle cells. After workouts, the muscles must be refueled with glycogen (the stored form of carbohydrates) to help with protein synthesis and mass building. Insulin increases nutrient storage and muscle replenishment after physical exercise by allowing more glucose, amino acids, and creatine to enter the muscles.
- Insulin allows greater blood flow to the muscles. According to this study, “insulin decreases vascular resistance and increases organ blood flow, especially in skeletal muscle tissue, indicating that insulin is a vasodilator.” An increased blood flow helps send more nutrients, glucose, and amino acids to the muscles, ultimately boosting muscle mass gain.
Is insulin an anabolic hormone?
Yes, insulin is a major anabolic hormone. Anabolic hormones, such as insulin, testosterone, growth hormones, and estrogen, promote muscle growth through anabolism when energy is used to construct complex molecules from smaller units.
The opposite process of catabolic hormones like cortisol, glucagon, or adrenaline inhibits muscle growth by breaking down molecules to use them for energy.
Is insulin a steroid?
Bodybuilders often have that misconception about insulin and think it's a steroid. But no, insulin is not a steroid.
Steroid hormones fall under the lipid category, while insulin is a peptide hormone formed with amino acids. However, it’s believed that insulin works side by side with anabolic androgenic steroids and growth hormones to boost muscle growth.
Related article: Does insulin expire? How long is it good for?
How do Bodybuilders use insulin?
Because the use of insulin for muscle growth isn’t legally nor medically approved, it’s not regulated. As a result, there’s no official insulin protocol for bodybuilders. Instead, the practice is rather individual and based on a try-and-see approach.
Several types of insulin
First, you must know that there are about 20 different types and brands of insulin on the market, and they all have different purposes, onset times, peak times, and duration.
Basal (long-acting) insulins are used to regulate fasting blood sugar levels in diabetes patients, while bolus (fast-acting) insulins act on after-meal blood sugars and carbohydrate intakes.
Because bodybuilders use insulin to help the muscles quickly absorb glucose and nutrients right after a workout, they use only bolus fast-acting types of insulin.
Related article: A beginner’s guide to basal and bolus insulins
Immediately after workout
The main purpose of taking insulin for bodybuilding is to promote muscle mass gain. This is achieved by injecting insulin right after a workout, along with the consumption of carbohydrates, so the insulin helps refuel the muscles faster and more efficiently after exercise.
Bodybuilders usually self-administer a shot of insulin within 15 minutes after a workout session to enter an anabolic state.
Related article: How to exercise safely when it’s hot and you have diabetes?
Insulin / carbohydrate ratio
Insulin use for muscle growth is only effective if combined with carbohydrate intake. Additionally, taking insulin without ingesting carbohydrates causes low blood sugar (hypoglycemia) that can lead to dangerous complications, including seizures, coma, and death.
A general rule is to consume at least 15 grams of carbohydrates for every unit of insulin you inject.
While we do not recommend using insulin for bodybuilding purposes, if you decide to do it anyways, you should use a glucose meter to track your blood sugar levels within the next 4 hours after an injection.
Related article: How to convert insulin units to mL?
Insulin for Bodybuilding: Benefits vs. Risks
The use of insulin for muscle growth is unsafe. Therefore, we do not recommend using insulin for bodybuilding or other purposes outside medically supervised diabetes treatment.
The risks and side effects may greatly outweigh the benefits, and several bodybuilders have died from insulin abuse and misuse.
Related article: Can hot weather and humidity affect blood sugar?
Hypoglycemia (low blood sugar)
The main risk associated with insulin abuse within a bodybuilding purpose is hypoglycemia (low blood sugar). Indeed, insulin is a hypoglycemic hormone medically used to lower blood sugar levels in diabetic patients.
When you inject a dose of insulin that’s not adapted to your carbohydrate intake (too much insulin) or level of physical activity, you’re at high risk of a blood sugar drop.
Symptoms of hypoglycemia include drowsiness, fast heartbeat, fatigue, hunger, sweating, irritability, paleness, shakiness, dizziness, and others.
While most of the time, eating or drinking fast-acting sugars (sugar, juices) quickly gets your blood glucose back to normal range, you may not be able to recover by yourself if you’ve injected a high dose of insulin.
Severe cases of hypoglycemia can indeed lead to confusion, seizures, coma, and even death. Therefore, they require immediate medical attention.
Country regulations and bodybuilding federations
Additionally, you must be aware of the legal situation in your country. While some countries don't regulate the use of insulin, and you can purchase it over the counter, others may have strict rules and forbid insulin use outside of medically approved insulin therapy for people with diabetes.
Last, some bodybuilding federations may consider insulin a banned substance. For example, the International Olympic Committee bans insulin outside its medical use (for athletes with insulin-dependent diabetes).
Related article: 10 famous athletes with diabetes who inspire us all!
 Fujita S, Rasmussen BB, Cadenas JG, Grady JJ, Volpi E. Effect of insulin on human skeletal muscle protein synthesis is modulated by insulin-induced changes in muscle blood flow and amino acid availability. Am J Physiol Endocrinol Metab. 2006 Oct;291(4):E745-54. doi: 10.1152/ajpendo.00271.2005. Epub 2006 May 16. PMID: 16705054; PMCID: PMC2804964.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804964/
 Kawasaki H, Kuroda S, Mimaki Y. [Vascular effects of insulin]. Nihon Yakurigaku Zasshi. 2000 May;115(5):287-94. Japanese. doi: 10.1254/fpj.115.287. PMID: 10872180. https://pubmed.ncbi.nlm.nih.gov/10872180/