IGF-1 LR3
A long-acting analog of insulin-like growth factor 1, engineered to stay active for far longer than the natural hormone. People run it for muscle growth and recovery, chasing hypertrophy and satellite-cell activation, often alongside a GH peptide like CJC-1295 or Ipamorelin.
Where to buy IGF-1 LR3, cheapest first.
Prices from 4 vendors across the market. We link straight to each vendor’s product page and grade vendors on public lab data, so you’re not just chasing the lowest number.
IGF-1 LR3
What IGF-1 LR3 actually does.
The simple version first, then a little more for the curious. No biochem degree required.
It mimics IGF-1, the growth signal your body makes downstream of growth hormone, but it sticks around for many hours instead of minutes, so it keeps telling muscle cells to grow and repair.
How it works
IGF-1 LR3 binds the IGF-1 receptor and switches on the PI3K/Akt pathway for protein synthesis and the MAPK/ERK pathway for cell proliferation. An arginine swap at position 3 plus an N-terminal extension cut its binding to IGFBPs, so it circulates free and active.
Where it acts
It acts on skeletal muscle in particular, activating satellite cells and driving both hypertrophy and, in lab models, true muscle-fiber hyperplasia. Because it also has insulin-like effects, it increases glucose uptake into muscle and fat tissue.
What people notice
Over a short cycle people report faster muscle gains, better pumps, and quicker recovery between hard sessions. The flip side is that the same insulin-like action can drop blood sugar, so timing around food matters.
Honest caveat: almost all of this comes from animal and cell studies, plus community reports. There are no controlled human trials supporting IGF-1 LR3 for muscle building, and its long half-life makes the hypoglycemia and theoretical overgrowth risks more serious, not less. It is not an approved medicine and is sold strictly for research use only. None of this is medical advice, talk to a licensed provider before starting anything.
How to take it.
IGF-1 LR3 is an injection, given intramuscularly into a muscle belly or subcutaneously into fat with a tiny insulin needle. It is not an oral peptide, so the injectable form is what people run. The routine is below; for cycling and timing, see the full guide.
Reconstitute the vial
Add bacteriostatic water down the side of the vial (a 1mg vial + 2mL = 500mcg/mL). Let it dissolve. Swirl gently, don't shake.
Draw your dose
On a U-100 insulin syringe, pull to your unit mark. 40mcg at 500mcg/mL is 8 units (0.08mL). Use the calculator if you're unsure.
Set the Z-track
Swab the muscle with alcohol, then pull the skin to one side and hold it. This Z-track method seals the channel after you withdraw so the dose stays put.
Insert at 90°, aspirate, inject slow
Go straight in to the hub, draw back slightly to check you are not in a vessel, then push slowly. Release the skin, rotate sites each time, and store the vial in the fridge between doses.
Inject into muscle: the shoulder (deltoid), the hip (ventrogluteal), or the outer thigh (vastus lateralis). Use the Z-track method and rotate every injection.
Don't do the math, let the calculator do it.
This is IGF-1 LR3's typical setup, already worked out. Change any value and the draw updates instantly.
Typical IGF-1 LR3 dose: about 20 to 50 mcg per day, run in short cycles of roughly four to six weeks, not continuously. Many people dose post-workout on training days, alongside food, to blunt the blood-sugar drop.
How to cycle IGF-1 LR3.
How long people run IGF-1 LR3, when to take a break, and the honest reasoning behind it.
Run in short cycles, not continuously.
A cycle just means a defined run of time on the peptide, followed by a break. For IGF-1 LR3 the common pattern is a short block of four to six weeks, then time off, rather than running it for months.
Why keep it short? Partly because the long-term human safety data does not exist, and partly because a sustained, long-acting growth signal is exactly the kind of thing you do not want to leave switched on indefinitely. The cautious and widely followed approach is a focused block, then a real break.
- Hold a short block, four to six weeks, at a steady daily or every-other-day schedule.
- Do not creep the dose up mid-cycle chasing more. The risks climb faster than the reward.
- Take a real break after a cycle before considering another. Any decision to repeat is a conversation for a licensed provider.
Want the full picture, on and off periods, the washout, stacking, and keeping your results? Read how peptide cycling works →
What's actually in the vial.
For 3 of these vendors we link the per-batch certificate itself (a specific lab report, COA PDF, or certificate image), and the purity below is read straight off that certificate. The rest link to the vendor's general lab-results page. We don't run the labs ourselves and we don't show a purity number unless it's printed on a certificate we link, so you can open the document and check it against the batch yourself.
| Vendor | Purity (per COA) | Batch / report | Certificate |
|---|---|---|---|
| Onyx Biolabs | 99.923% | IGF-2026-0320 | View COA ↗ |
| Pure Rawz | 99.37% | IGH902 | View COA ↗ |
| Swiss Chems | 99% | AY6566 | View COA ↗ |
| Penguin Peptides | see lab page | not shown | Lab results ↗ |
What people pair it with.
IGF-1 LR3 is usually run in a muscle-building block rather than alone. These are the combinations the community reaches for when growth is the goal.
Growth & recovery
The most common GH-and-IGF stack. CJC-1295 and Ipamorelin push your own growth-hormone release, while IGF-1 LR3 adds the downstream growth signal directly. The classic mass-and-recovery trio.
View stack →Oral GH base
MK-677 is an oral pill that raises GH and IGF-1 around the clock; IGF-1 LR3 layers a direct, long-acting IGF signal on top. Easy GH base plus a targeted growth push.
View stack →Build & repair
Pairs the growth signal with the two go-to recovery peptides, so you are building muscle while supporting tendon, ligament, and soft-tissue repair through a hard block.
View stack →In the same corner.
Other muscle and growth-hormone peptides people compare against IGF-1 LR3.
Questions, answered straight.
Is IGF-1 LR3 legal?
IGF-1 LR3 isn't an approved drug, and it isn't sold for human use. The vendors we compare offer it strictly for research use only. It's also banned at all times by WADA, so competing athletes should steer clear. Rules vary by country, so check what applies where you are.
What does research use only actually mean?
It means the product is sold for laboratory and research purposes, not as a supplement or medicine for people. It hasn't been reviewed or approved for human use by the FDA. We aggregate prices and public lab data so you can see the landscape; what you do with that is between you and a licensed provider.
Why does everyone warn about low blood sugar?
Because IGF-1 LR3 has insulin-like effects, and its long half-life means those effects can persist for many hours. Blood-sugar drops in the 60 to 120 minutes after a dose are commonly reported. People dose around food and watch for shakiness, sweating, and dizziness; this is a real risk, not a footnote.
How do I store it?
Keep the sealed, freeze-dried vial in the fridge and out of direct light. Once mixed with bacteriostatic water, store it refrigerated and use it within a few weeks. Don't freeze a reconstituted vial. IGF-1 LR3 is delicate, so handle it gently.
Intramuscular or subcutaneous?
Either works. Intramuscular into a muscle belly is common with IGF-1 LR3; some people inject subcutaneously into fat instead. After reconstitution it's the same draw either way. IGF-1 LR3 isn't an oral peptide, so skip the capsule versions.