Peptide guide

IGF-1 LR3

Long R3 IGF-1 — a long-acting synthetic analog of insulin-like growth factor 1, studied for growth and tissue repair.

IGF-1 LR3 is a re-engineered version of insulin-like growth factor 1, modified so it stays active in the body for roughly a day instead of minutes. It was originally built as a cell-culture reagent for biotech manufacturing, and it carries no human approval as a drug. People run it anyway, mostly for muscle growth and recovery, which makes two questions practical: how to handle the real low-blood-sugar risk it brings, and how not to get scammed buying it.

By the Zapify Research team

Reviewed against 10 clinical & research sources · Updated June 2026 · Educational use only

Type: IGF-1 analog83-aa, Long R3
Route: Subcutaneous
Typical dose: 20–50 mcg/dayreported range
Cycle: 4–6 wks onthen off to reset receptors
Storage: Mixed: 2–4 wksSealed: months
Status: Not FDA-approved

What is IGF-1 LR3?

A re-engineered IGF-1 whose arginine swap and 13-amino-acid extension stretch its half-life to roughly 20-30 hours; it's a repurposed cell-culture reagent, never FDA-approved or tested for safety in humans.

IGF-1 LR3 is a modified version of insulin-like growth factor 1, a hormone your body makes naturally. Native IGF-1 is the messenger growth hormone works through: when GH hits the liver, the liver releases IGF-1, and IGF-1 is what actually tells muscle and other tissue to grow and repair. The molecule sold as IGF-1 LR3 is the same idea rebuilt to last far longer in the body.

Two changes do the heavy lifting. An arginine swap at position 3 and a 13-amino-acid extension on the front end make the molecule bind much more weakly to the binding proteins that normally grab IGF-1 and pull it out of circulation. With those proteins largely sidestepped, more of the peptide stays free and active, and its working half-life stretches from roughly 15 minutes for native IGF-1 to somewhere around 20 to 30 hours. The whole molecule runs 83 amino acids against the natural 70.

Worth knowing where this one actually comes from: LR3 IGF-1 was engineered as a cell-culture reagent, a supplement that helps mammalian cells grow in industrial tanks producing biologic drugs. That is its real, intended job. The vials people inject are that same lab reagent repurposed, which is a different thing from a medicine designed and tested for a body.

IGF-1 LR3 isn't FDA-approved for anything, and it has never been systematically tested for safety in humans. A different molecule — native IGF-1, sold as mecasermin — is an approved prescription drug for a rare growth disorder, but the LR3 analog is not that drug and doesn't share its approval. Treat it as an experimental research reagent, not a proven medicine.

What is it studied for?

IGF-1 biology is deeply researched, but the injected analog was characterized for cell culture, not living bodies, and has no standardized human trials behind that use.

The interesting thing about IGF-1 LR3 is that the biology of IGF-1 itself is well understood, while the analog people inject is barely studied in living bodies at all. IGF-1 is one of the most-researched growth factors in science. LR3 IGF-1 specifically was characterized for cell-culture performance, not for what it does when a person injects it, and it has no standardized human trials behind that use.

Evidence base, by subject

ExtensiveCell-culture & animal work

NoneHuman trials of the LR3 analog

The reported interest clusters in a few areas, all extrapolated from IGF-1 biology and animal work rather than shown for the injected analog:

Muscle growthIGF-1 drives protein synthesis and activates satellite cells, the repair cells that build new muscle fiber. This is the headline reason it's used.

Tissue repairThe same growth and cell-proliferation signaling is studied for recovery from training, injury, and surgery.

Nutrient partitioningIGF-1 shares signaling with insulin and pushes glucose and amino acids into cells, which is also the source of its low-blood-sugar risk.

Mechanistically the front half of the story is solid: LR3 binds the IGF-1 receptor and fires the PI3K/Akt and MAPK pathways that build tissue, and because it dodges the binding proteins it does this more persistently than native IGF-1. What's open is everything downstream in a real person — how that sustained, supraphysiological signaling plays out over weeks, and whether the muscle results people chase actually follow. That part rests on inference, not human data.

Why people use it

People run it for muscle growth, recovery, and steroid stacking, but no human trial shows it builds muscle and it was never designed to go into a person.

Most people who try IGF-1 LR3 are chasing one of a few outcomes. These are the reasons they reach for it, not evidence that it delivers:

Adding muscle mass, where the IGF-1 pathway's role in hypertrophy is the whole draw.
Faster recovery between hard training sessions, treating it as a growth-and-repair amplifier.
Stacking it onto a steroid or growth-hormone cycle, on the theory that it pushes the same anabolic signaling from a different angle.
Curiosity about the nutrient-partitioning effect, wanting more of what's eaten to land in muscle.

No human trial has shown IGF-1 LR3 will build muscle or speed recovery, and it was never designed to go into a person. What's real is a deeply characterized growth pathway, a molecule that demonstrably activates it, and a long half-life that keeps the signal up. That's a coherent reason to be curious. It isn't proof, the safety picture is genuinely thinner than for most peptides people run, and it won't substitute for the training, food, and sleep that actually move the needle.

How to reconstitute IGF-1 LR3

A 1 mg vial mixed with 1 mL bacteriostatic water gives 1000 mcg/mL, putting a 30 mcg dose at just 3 units, the tiny mark that trips people up.

Your vial arrives as a small amount of dry powder, often 1 mg. Before use it's mixed into a liquid, a step called reconstitution. The mechanics are the same as any research peptide, and the small total amount in the vial makes the draw math matter more than usual.

Step 1Start with powderWipe the rubber stopper with an alcohol swab.

Step 2Add bac. waterRun it slowly down the inside wall — never shake.

Step 3Draw your doseThe calculator gives the exact units to draw to.

Wipe the rubber stopper with an alcohol swab first, every time.
Use bacteriostatic water, not plain sterile water and not saline. The trace of benzyl alcohol in it holds back bacteria, which matters because you'll be drawing from the same vial for weeks.
Add the water slowly, running it down the inside glass wall. Don't blast it straight onto the powder.
Don't shake it. Swirl gently and let it dissolve on its own. Shaking foams the solution and can damage the peptide.

A common setup is a 1 mg vial mixed with 1 mL of bacteriostatic water, which gives 1000 mcg/mL. On a U-100 insulin syringe, that puts a 30 mcg dose at just 3 units — a very small mark, which is exactly why the small vial trips people up. Add 2 mL instead and the same 30 mcg becomes 6 units. The water never changes how much peptide is in the vial; it only sets the concentration, which decides how far you draw. You can't ruin it with too much or too little, you only change the math, and that's what the calculator handles.

Calculate your exact IGF-1 LR3 reconstitution →

Dose & units

No dose is FDA-approved; reports cluster at 20-50 mcg daily, run 4-6 weeks on then off, with pushing past 80 mcg adding side effects faster than results.

There is no FDA-approved dose for IGF-1 LR3. Everything below is a range that clinics and write-ups report, not a medical standard, and because the analog has no human safety trials these numbers rest on convention rather than evidence. Decide what goes into your body with a licensed provider, not with this page.

Typical range

The range reported most often is 20–50 mcg per day, with beginners usually starting at 20–40 mcg to gauge tolerance. (A microgram, or mcg, is a thousandth of a milligram.) Reports of 60–100 mcg a day exist in advanced bodybuilding circles, but the consistent observation is that pushing past roughly 80 mcg tends to add side effects faster than results.

Timing

Most reported timing is post-workout on training days, which lines up the injection with elevated blood glucose and a planned meal — both of which blunt the low-blood-sugar risk. On rest days the common timing is morning with food. Injecting on an empty stomach is the setup people specifically warn against.

Cycling

Sources are consistent that this runs as a short course, not something you stay on: commonly 4–6 weeks on, then several weeks off. The off period isn't optional padding. Daily IGF-1 receptor activation downregulates the receptor, so continuous use quietly loses effect while the side-effect exposure keeps accumulating. The break is what resets sensitivity.

On4–6 weeks

Off4–6 weeks

On a small vial like this, eyeballing the mark is how people accidentally take several times their intended dose. The calculator turns your vial size, water, and dose into the precise number of units to draw.

Get your exact units →

Storage

Sealed powder keeps for months but IGF-1 analogs prefer cold or frozen; once mixed, refrigerate at 2-8 C and use within about two to four weeks.

Sealed & dryDry, unmixed vial keeps for months and travels fine, though IGF-1 analogs prefer being kept cold or frozen even sealed.

ReconstitutedRefrigerate at 2-8 C in the main compartment, use within about 2-4 weeks, never freeze, keep out of light, and discard if cloudy.

You'll see longer windows quoted for peptide vials. Those figures are beyond-use dates for a sealed, stability-tested vial, and they stop applying the moment you add water. A mixed vial runs on the shorter clock instead, because that's how long the preservative in bacteriostatic water reliably keeps the solution clean once you're drawing from it.

That limit is about contamination, not potency, though growth factors are also fragile proteins that degrade with heat and agitation, so cold and still matters here more than with hardier peptides. Reconstitute with plain sterile water instead of bacteriostatic and you drop to a day or two, since there's no preservative holding bacteria back.

Don't freeze a reconstituted vial, keep it out of direct light, write the mix date on the label, and throw it out if the solution ever turns cloudy or discolored, whatever the date says.

Side effects & safety

Hypoglycemia is the most common and dangerous effect since IGF-1 mimics insulin, and sustained high signaling is a known cancer growth driver with no human safety data to bound the risk.

The safety profile here deserves more weight than the usual recovery peptide, because IGF-1 LR3 acts on a powerful growth pathway and has no human safety data to bound the risk. The reports come from animal work, the biology of IGF-1, and user accounts, not controlled trials.

Low blood sugar (hypoglycemia): the most common and most dangerous effect. IGF-1 mimics insulin and drives glucose into cells, which can drop blood sugar into shakiness, sweating, confusion, or worse, especially when dosed away from food.
Localized swelling or tissue growth at the injection site, a direct read on what the molecule does.
Joint pain and a feeling of water retention or puffiness.
Headaches and, in some reports, lightheadedness.

The hypoglycemia risk is real and can be serious. Keep fast-acting carbohydrate on hand whenever you dose, never inject on an empty stomach, and don't drive until you know how you respond. The deeper concern is longer-range: sustained high IGF-1 signaling is a known growth driver for several cancers, and chronic excess is what produces the organ and bone overgrowth seen in acromegaly. That risk is mechanistic and unproven for short courses, but it's the reason a history of cancer, diabetes, pregnancy, or breastfeeding should rule this out without a doctor's involvement.

If you compete, IGF-1 LR3 is banned. WADA lists IGF-1 and its analogs under S2 (peptide hormones, growth factors, and mimetics), prohibited at all times, in and out of competition. A positive test is a doping violation carrying a multi-year ban.

And the biggest immediate risk isn't even the molecule's biology. It's whether the vial really contains IGF-1 LR3, at the strength on the label, and properly folded rather than degraded. That comes down to where you buy it.

How to vet a source

It's a folded 83-amino-acid protein that's hard to make and easy to fake invisibly, so demand a batch-specific, third-party COA and match the lot number to your vial.

IGF-1 LR3 is harder to make and easier to fake than a short peptide. It's a folded 83-amino-acid protein, and a vial can be underdosed, misfolded into something inactive, or not the compound at all without any visible sign in the powder. In an unregulated market where independently tested vials regularly come back wrong, where you buy matters more than almost anything else here. The one document that separates a real seller from a gamble is a certificate of analysis: a third-party lab's report on what's actually in the vial.

A real COA shows

An identity test (usually mass spectrometry) confirming the peptide is what the label says.
A purity figure from HPLC, typically 98% or higher.
A lot or batch number that matches the number printed on your vial.
A named, independent accredited lab and a recent test date.

Walk away if

There’s no COA, or it’s a generic image with no lot number.
The “certificate” comes from the seller instead of a third-party lab.
The lot number doesn’t match your vial, or there isn’t one at all.
It’s a flat image you can’t trace back to the lab that issued it.

That's the standard worth holding any seller to, ours included. Ask for the batch-specific COA before you buy, match the lot number to your vial, and don't accept a screenshot in place of a traceable report.

See the Zapify compound catalog →

Common questions about IGF-1 LR3

Is IGF-1 LR3 approved or proven to work in people?

No. It isn't FDA-approved for any use and has never been systematically tested for safety in humans. It was engineered as a cell-culture reagent for biotech manufacturing, not as a drug. Native IGF-1 (mecasermin) is an approved prescription medicine for a rare growth disorder, but that's a different molecule from the LR3 analog and doesn't lend it any approval.

What's the difference between IGF-1 LR3 and regular IGF-1?

Both hit the same IGF-1 receptor, but LR3 is rebuilt to last. An arginine substitution at position 3 plus a 13-amino-acid extension make it bind far more weakly to the binding proteins that normally clear IGF-1, so its working half-life stretches from roughly 15 minutes to around 20–30 hours. That sustained, mostly-free exposure is also what amplifies its risks.

Why is hypoglycemia such a concern with IGF-1 LR3?

IGF-1 shares signaling with insulin and pushes glucose into cells, so it can lower blood sugar — sometimes sharply. The long half-life means that effect lingers. The reported safeguards are dosing post-workout or with a meal, never on an empty stomach, and keeping fast-acting carbohydrate on hand. Anyone with diabetes or blood-sugar issues should not approach this without a doctor.

Do I have to cycle off it?

The reported protocols all build in an off period, and not just as a precaution. Daily IGF-1 receptor activation downregulates the receptor, so continuous use loses effect over time while the side-effect exposure keeps stacking. Commonly that's 4–6 weeks on followed by a comparable break, which is meant to restore receptor sensitivity.

Is IGF-1 LR3 banned in sport?

Yes. WADA lists IGF-1 and its analogs, including LR3, under category S2 (peptide hormones, growth factors, and mimetics), prohibited at all times — in and out of competition. Detection windows and a multi-year ban for a first violation make it a serious anti-doping risk for any tested athlete.

References

This page is for research and educational purposes only. It is not medical advice or a recommendation to use any compound. The dose ranges shown are reported by clinics and research literature, not validated medical standards, and IGF-1 LR3 is not FDA-approved. Talk to a licensed medical provider about anything you put in your body.