Peptide & Experimental

Insulin in bodybuilding

Approved prescription-only diabetes medicine (peptide hormone); misused for muscle building, banned in sport at all times · insulin misuse, non-medical insulin use, insulin as a doping agent

9 min read 10 sources, checked November 12, 2026

In the BK-Score: Hype far ahead of evidence – human evidence 3 out of 10, safety data 5 out of 10. The marketing promises much more than the thin data can carry so far.

Insulin is one of the most important medicines of all: without insulin, people with type 1 diabetes cannot live. In bodybuilding it is injected without diabetes because it slows the breakdown of muscle protein and brings glucose into the muscles. This page explains what of this is supported and where the risks lie.

In short

The idea behind insulin in bodybuilding has a kernel of truth. In short infusion experiments in humans, insulin clearly slows the breakdown of muscle protein and improves protein balance, as a meta-analysis shows. Whether this leads to more muscle over weeks in healthy people who train has, however, not been measured in any controlled study. In surveys, some steroid users also use insulin, and among recreational bodybuilders who use hormones more than one in three. More than half of the respondents in one survey reported hypoglycemia. Case reports describe coma, and in Australia a court found in 2021 that a 31-year-old bodybuilder had died of brain damage caused by self-injected insulin.

What insulin is

Insulin is a peptide hormone of the pancreas. It lowers blood sugar by bringing glucose into muscle, fat and liver cells, and it also controls protein and fat metabolism. As a medicine it is approved for the treatment of diabetes and is prescription-only; one example is insulin glargine, approved in the EU since June 9, 2000.

In bodybuilding and strength sports, insulin is injected by people without diabetes, usually together with anabolic steroids and often with growth hormone. The hope: less muscle breakdown and more glucose stored as energy in the muscle. In addition, insulin is difficult to detect in doping tests; researchers are therefore looking for indirect markers in the blood.

How it works

In muscle, insulin acts mainly as a brake on protein breakdown. A meta-analysis of infusion studies with 173 people shows: the breakdown of muscle protein fell clearly, and protein balance became more positive. Insulin increased the synthesis of muscle protein only when more amino acids entered the blood at the same time; without this supply it did not change.

The same effect is the danger. Insulin pulls glucose out of the blood, and the brain depends on glucose. If blood sugar falls too low, unconsciousness and coma threaten; if the state persists, the brain can be permanently damaged.

What is well supported

Insulin slows muscle breakdown. In infusion experiments in humans, the breakdown of muscle protein fell clearly and protein balance improved (meta-analysis, 173 people).
Synthesis only with amino acids. Insulin increased the synthesis of muscle protein only when more amino acids were available at the same time.
Insulin really is used in bodybuilding. Several surveys document its use, almost always together with steroids.
Hypoglycemia is well known. It is the most common side effect even in medically supervised diabetes therapy.

What the studies show

Abdulla 2016: meta-analysis on muscle metabolism

Of 104 papers examined, 44 studies were included in the systematic review and 25 with a combined 173 people in the meta-analysis. They measured how the synthesis and breakdown of muscle protein in the leg change during an insulin infusion. Insulin clearly reduced breakdown and improved net balance. Overall it did not increase synthesis, but it did when amino acid delivery was increased. These are short laboratory experiments with insulin infusion, not training studies.

What users report

Published surveys give an impression of how widespread insulin is and what users experience. In an online survey of 500 steroid users, a quarter said they also used growth hormone and insulin for muscle building (Parkinson and Evans 2006). A case series from an online survey describes 41 non-diabetic insulin users: on average 30.7 years old, almost all men, 95.1 percent also took steroids, on average 16 performance-enhancing drugs per year. 56.8 percent reported hypoglycemia, one reported unconsciousness (Ip 2012). Among 92 recreational bodybuilders, 43 percent used hormones according to an anonymous questionnaire, and 38 percent of these used insulin (Di Girolamo 2024). All three are based on self-reports and are not representative.

Di Girolamo 2024: metabolic values

The researchers compared 92 recreational bodybuilders with 45 healthy controls. In users of insulin and/or growth hormone, HDL cholesterol was lower, liver values were higher in hormone-using bodybuilders, and insulin was associated with an altered ratio of the liver values ALT to AST. The authors see these as possible markers for indirect detection of insulin doping.

Heidet 2019: coma in a bodybuilder

A 30-year-old bodybuilder arrived at the emergency department in a coma due to severe hypoglycemia. His blood sugar could only be stabilized with repeated glucose infusions. Only later did it emerge that he had secretly injected insulin. The authors advise emergency physicians to consider insulin in cases of unexplained, treatment-resistant hypoglycemia in young strength athletes.

Coroners Court of New South Wales 2021: a death

An Australian court investigated the death of a 31-year-old personal trainer who had taken part in his first bodybuilding competition shortly before. He injected insulin in a gym bathroom, rapidly developed hypoglycemia, lost consciousness and was not found for around 20 hours. He died of brain damage due to lack of oxygen, caused by the injected insulin. The court found that early discovery could have saved his life and recommended, among other things, a dedicated fact sheet from the health authority on the risks of non-prescribed insulin.

Where the data stop

No training study. Whether insulin brings more muscle mass or strength over weeks in healthy people who train has not been examined in any controlled study. Reviews speak of a lack of robust human data.
A lab experiment is not everyday life. The data on muscle metabolism come from short infusion experiments in the laboratory, not from injections without monitoring.
Insulin rarely comes alone. Almost all users also take steroids and often growth hormone; the share attributable to insulin cannot be separated from surveys.
How often it goes wrong is unknown. Surveys and case reports show that hypoglycemia is common, but not how often it causes lasting damage or death.

Status, approval and legal

Insulins are approved prescription-only medicines for the treatment of diabetes, in the EU for example insulin glargine since June 9, 2000. There is no approval for muscle building.

In Germany, “insulins” are listed in the annex of the German Anti-Doping Act: acquiring, possessing and bringing into the country non-small quantities for doping in sport are prohibited, as are manufacturing, trading, supplying and prescribing for doping purposes; both are punishable. In sport, insulins are on the WADA Prohibited List 2026 under S4.4.2, insulins and insulin mimetics, and are banned at all times.

Safety

The main danger is hypoglycemia. It is the most common side effect even in medically supervised diabetes therapy, in more than 1 in 10 people treated. Without diabetes, without training and without blood sugar measurement, it is added to the mix when training, dieting and insulin coincide. In one survey, 56.8 percent of non-diabetic insulin users reported hypoglycemia. Case reports describe a coma that required repeated glucose infusions, and a court established a death from insulin-related brain damage. In addition, users of insulin and growth hormone had lower HDL and altered liver values. On top of this come the risks of the drugs with which insulin is almost always combined, see anabolic steroids.

Severe hypoglycemia can lead to unconsciousness within a short time, and anyone who is alone then can no longer help themselves. In the Australian case, in the court’s assessment, earlier discovery could have saved his life.

BK-Score Hype far ahead of evidence

Human evidence		3
Mechanism		8
Safety data		5
Hype gap		2
Track record of use		5

Evidence 3, because in humans there are only short infusion experiments in which insulin slows the breakdown of muscle protein (meta-analysis, 173 people, Abdulla 2016), but no controlled study of muscle mass or strength in healthy people who train; direction therefore open. Mechanism 8, because the effect of insulin on glucose uptake and protein metabolism in muscle is well described, but the path from slowed protein breakdown to more muscle in training has not been measured. Safety 5, because hypoglycemia is known as the most common side effect from diabetes therapy (EMA), but for use without diabetes there are only surveys (Ip 2012, Di Girolamo 2024), case reports (Heidet 2019) and one death examined by a court (Coroners Court NSW 2021) – a medium number means partly studied, not harmless. Hype 2, because insulin is regarded in the scene as a muscle-building drug, although there is not a single efficacy study for this. Use 5, because insulin has been used in diabetes therapy for decades, but for the purpose of this entry there is only uncontrolled experience from the scene, almost always alongside other drugs (Parkinson and Evans 2006). For comparison: clenbuterol (4/7/4/2/5), HGH (8/9/8/3/9), liothyronine (4/9/6/3/8).

The score rates the state of knowledge, not the substance. A high safety-data value means well studied – not harmless.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about Insulin in bodybuilding

Does insulin build muscle?

It is established that insulin slows the breakdown of muscle protein and improves protein balance in short infusion experiments; it increases synthesis only when plenty of amino acids are available. Whether healthy people who train build more muscle over weeks as a result has not been examined in any controlled study.

How dangerous is insulin without diabetes?

The main danger is hypoglycemia. In a survey of 41 non-diabetic insulin users, 56.8 percent reported it, and one reported unconsciousness. Case reports describe coma, and in Australia a court established in 2021 that a 31-year-old bodybuilder died of insulin-related brain damage.

How widespread is insulin in bodybuilding?

There are no robust figures, only surveys. In an online survey of 500 steroid users, a quarter also took growth hormone and insulin. Among 92 recreational bodybuilders surveyed, 43 percent used hormones, and 38 percent of these used insulin.

Is insulin banned in sport?

Yes. Insulins are on the WADA Prohibited List under S4.4.2 and are banned at all times. In Germany they are listed in the annex of the German Anti-Doping Act; acquiring and possessing non-small quantities for doping are prohibited, as are trading and supplying for doping purposes.

Is insulin prescription-only?

Yes. Insulins are prescription-only medicines, approved for the treatment of diabetes. There is no approval for muscle building.

Sources

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-11-12.