BIOHACKPHARMStack Analyzer

IGF-1 LR3

Long R3 IGF-1, LR3 IGF-1, LR3-IGF-I, Long Arg3 IGF-I

Forms: Related forms: DES(1-3) IGF-1 (a short-acting research analogue) and mecasermin (Increlex), the approved recombinant IGF-1 for severe primary IGF-1 deficiency in children.

Growth hormone & secretagoguesNot approved for humansWADA S2 · prohibitedEvidence: animal data onlyExtreme risk

Lab-made IGF-1 analogue (83 amino acids) that barely binds IGF-binding proteins, so far more of it is free to act; 2–3 times more potent than IGF-1 in animals. Never studied in humans.

Legal status: Laboratory reagent never approved for human use; sold as a 'research peptide'. Status varies by country.

What it gives

What people use it for and what the sources report. Strength is a general category from the literature: mild, clear or strong.

Purpose

Made as a reagent for cell culture and lab research; no medical use. In sport: a 'research peptide' used for muscle growth, recovery and 'nutrient partitioning' — claims without any human data.

What people seek and what studies show

Used for muscle growth, recovery and 'nutrient partitioning'. It was never tested in people. In growing rats it raised weight gain and nitrogen retention at far lower amounts than IGF-1, with body proportions unchanged; in rats with drug-induced wasting it limited losses, but the gut grew most, by up to 45%. Muscle gain in people is unproven; its insulin-like action makes low blood sugar the main immediate danger.

Effects

Muscle growthRecovery

Evidence: Animal data only — effects in people are unproven

Possible side effects

With an extreme-risk substance some of these can be life-threatening or permanent; no dose, test or early sign makes it safe. Below — what each risk looks like; the signs that need urgent help are in block 04.

8 possible side effects

level · how often it is reported
High
Dangerous low blood sugar
Insulin-like, stronger and longer than IGF-1 in animals; medical IGF-1 caused seizures and unconsciousness. Severe lows can kill, more so with insulin, fasting or alcohol. No measure makes use safe.
How to notice: Shaking, sweating, sudden hunger, confusion.
possible
Elevated
Black-market quality risk (fakes, contamination)
Sold as a laboratory reagent: identity, potency and sterility are unverified.
How to notice: Unexpected effects, pain or infection, a stronger or weaker effect than expected.
common
Elevated
Abnormal tissue growth (theoretical cancer risk)
A direct growth signal to most cells, including tumor cells; in animals it enlarged the gut, kidneys and spleen. Medical IGF-1 is contraindicated in cancer.
How to notice: No direct signs — the point is not to fuel existing growths.
possible
Moderate
Unknown long-term safety (little human data)
Never tested in humans: there are no safety data for any duration of use.
How to notice: Nothing to notice — the risk is what is not yet known.
common
Low
Water retention / bloating
Medical IGF-1 caused swelling of the face and hands in adult trials; for LR3 this is unstudied.
How to notice: Puffy face and ankles, softer look, quick weight jumps.
possible
Low
Joint & muscle pain
Jaw tenderness, joint and muscle pain made adults stop medical IGF-1 in trials; for LR3 this is unstudied.
How to notice: Aching or stiff joints, muscle aches.
possible
Low
Injection pain, infection, oil cough
Local reactions; a non-sterile 'research' product raises the risk of infection.
How to notice: Soreness, lumps; a short coughing fit right after an injection.
possible
Low
Numbness, tingling, carpal tunnel
Higher IGF-1 is linked to carpal tunnel syndrome in large population studies, and medical IGF-1 caused hand swelling; for LR3 this is unstudied.
How to notice: Numb or tingling fingers, especially at night.
rare

How to lower the risks

Extreme risk

Extreme risk. No measure makes using this substance for sport safe: severe, including life-threatening, consequences are possible. The only reliable way to avoid these risks is not to use it.

Warning signs that need urgent help are listed in block 04.

Check-ups and blood tests

For an extreme-risk substance there is no testing schedule.

No testing schedule makes this substance safe, so there is no plan of tests here. If it has already been taken, watch for the urgent warning signs on this page and see a doctor — tell them exactly what was taken.

Get medical help at once if

  • Shaking, cold sweat, sudden hunger, confusion — fast sugar at once; very drowsy, unable to swallow or unconscious — nothing by mouth, call emergency services, glucagon if prescribed. Night sweats or nightmares can mean lows in sleep.
  • A new lump (including in the neck), trouble swallowing or persistent hoarseness, unexplained weight loss, or blood in stool or urine — see a doctor promptly.

In an emergency, call your local emergency number.

Myth & fact

Myth

“IGF-1 LR3 is the pure 'muscle-building part' of growth hormone.”

Fact

It is a cell-culture reagent never tested in humans; growth effects in rats don't prove muscle gain (in one pig study it even slowed growth), while low blood sugar is a real, immediate risk.

Combinations

Dangerous combinationInsulin with another sugar-lowering substance

Each of these lowers blood sugar in its own way, so with insulin the lows come deeper, last longer and are harder to predict. Confusion, sweating or drowsiness is an emergency; a severe low can kill.

Insulin (rapid- and short-acting)MetforminSemaglutideTirzepatideRetatrutide (investigational triple agonist)BerberineAlpha-lipoic acidLiraglutideCagrilintide (investigational amylin analogue)Mecasermin (recombinant IGF-1, Increlex)DES(1-3) IGF-1
Dangerous combinationIGF-1 LR3 with another sugar-lowering substance

IGF-1 LR3 acts like a long-lasting insulin. Other sugar-lowering substances add to it, so lows come deeper and last longer; confusion, sweating or drowsiness is an emergency.

MetforminSemaglutideTirzepatideRetatrutide (investigational triple agonist)BerberineAlpha-lipoic acidLiraglutideCagrilintide (investigational amylin analogue)Mecasermin (recombinant IGF-1, Increlex)DES(1-3) IGF-1
Dangerous combinationA beta-blocker hides the warning signs of low sugar

A racing pulse and tremor are the body's early alarm for low blood sugar. Nebivolol blunts them, so a dangerous low can go unnoticed until it shows as confusion or fainting.

NebivololInsulin (rapid- and short-acting)Mecasermin (recombinant IGF-1, Increlex)DES(1-3) IGF-1
CautionGlucocorticoid with insulin, IGF-1 or a GLP-1 drug

Glucocorticoids raise blood sugar, after a depot injection often for days, and work against insulin, IGF-1 and GLP-1 drugs. Sugar can run high while the glucocorticoid acts and then fall as its effect wears off while the sugar-lowering drug keeps working. Only glucose checks show these swings.

Insulin (rapid- and short-acting)Mecasermin (recombinant IGF-1, Increlex)DES(1-3) IGF-1SemaglutideTirzepatideRetatrutide (investigational triple agonist)Liraglutide
Dangerous combinationA beta-blocker hides the warning signs of low sugar

A racing pulse is one of the body's early alarms for low blood sugar. Bisoprolol and carvedilol blunt it, so a dangerous low can go unnoticed until it shows as confusion or fainting. Carvedilol, which also blocks beta-2 receptors, can in addition make a low deeper and slower to recover from.

Insulin (rapid- and short-acting)Mecasermin (recombinant IGF-1, Increlex)DES(1-3) IGF-1

Sources

Tomas FM et al. IGF-I variants which bind poorly to IGF-binding proteins (incl. LR3-IGF-I) show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys. J Endocrinol 1997 (opens in a new tab)DailyMed: INCRELEX (mecasermin, recombinant IGF-1) prescribing information (opens in a new tab)Dominikowski A et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis. Front Endocrinol 2026 (opens in a new tab)