IGF-1 LR3
Also called Long R3 IGF-1
IGF-1 is the messenger growth hormone actually sends.
The published research here is animal and laboratory work. The ranges below come from community-reported dosing and results — what people have settled on in practice, and what they report happening.
- Body composition
- Recovery & injury
The quick answer
IGF-1 is the messenger growth hormone actually sends. GH goes to the liver, the liver makes IGF-1, and IGF-1 does most of what people credit GH with. The LR3 version is modified so the body's binding proteins cannot mop it up, which makes it far longer-lived and considerably stronger than the natural version.
What it is not
Not a releaser, and not something the pituitary regulates. The feedback loop that makes Sermorelin hard to overshoot does not exist here.
Why people use it
💪 Muscle fullness, reported early; 🩹 Recovery; 🎯 Skips the pituitary, so age-related decline upstream does not limit it
What people report using
These are ranges other people have reported running. They are here so you can see what has actually been done — they are not medical advice and not a recommendation for you.
- How often
- Daily, 4–6 weeks
- Route
- subcutaneous
- Evidence for this
- Animal and lab research
Muscle fullness within days is the common report.
What to expect, and when
Days 3-10: fullness and pump. Week 2-4: recovery. Cycles are described as weeks, not months.
Side effects, and what people do about them
Low blood sugar dominates the discussion - lightheadedness, sweating, shakiness - and it is why people eat around dosing. Injection-site reactions. Anything that pushes IGF-1 signalling upward is debated openly in the longevity communities, who read it as the opposite of what they want.
Go deeper
Open these only if you want them.
How it actually works
Long R3 IGF-1: an arginine substitution plus a thirteen-amino-acid extension that sharply reduces binding-protein affinity, stretching half-life from minutes to roughly a day and multiplying potency. Acts directly at the IGF-1 receptor, downstream of the pituitary entirely.
More on the evidence
The LR3 analogue itself has no human trial. Distinct from mecasermin.
The case against
No human trials for this use. The IGF-1-and-longevity literature genuinely runs against it, which is a real consideration to weigh rather than a scare.
What people report, in full
IGF-1 LR3 splits the community, and the split itself is the useful information. Bodybuilding discussion is positive about the short-term feel - fullness and pump within days. Longevity discussion treats raised IGF-1 as precisely the thing it is trying to lower, and points at this compound as the example of what not to run. Both groups are describing the same biology and reaching opposite conclusions because they want opposite things, which is worth knowing before you read either one. The practical advice that repeats is about blood sugar: people dose around a meal, and nearly all the reports of feeling awful come from dosing fasted. Cycles are described as short and defined, and nobody experienced recommends running it continuously.
Sources and review
https://pubmed.ncbi.nlm.nih.gov/7561636/
https://pubmed.ncbi.nlm.nih.gov/11472075/
Last reviewed 2026-09-08.
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