IGF-1 LR3 (Long R3 IGF-1 analogue)

Also referred to as Long R3 IGF-1, insulin-like growth factor 1 LR3 analogue.

Status: Investigational. IGF-1 LR3 is not an FDA-approved drug product and is not an approved therapy for any indication. It is a laboratory reagent, a modified analogue of human IGF-1 originally engineered to be a more stable research tool for studying growth factor biology in cell culture, not a substance developed or tested for human administration.

IGF-1 LR3 is a laboratory-engineered analogue of insulin-like growth factor 1, modified to resist degradation for use as a research reagent in cell culture, not as a therapeutic product. It is not an approved product for human use, and it should not be treated as a variant of an approved medicine. Because it acts on growth factor signalling, it raises genuine concerns about effects on cell proliferation and about severe blood sugar drops, concerns that are taken seriously in the scientific literature on IGF-1 biology generally. There is no controlled human trial establishing a safety profile for this specific analogue.

What it is

IGF-1 LR3 is a synthetic 83-amino-acid analogue of human IGF-1 with an amino acid substitution and an added N-terminal extension, changes made specifically to reduce binding to IGF-binding proteins so the molecule remains more biologically active for longer in laboratory assays. It was designed and is sold as a research reagent for cell biology, not as a pharmaceutical candidate that has gone through any development pathway toward human use. Material marketed for personal use is unregulated and not equivalent to any approved growth factor therapy.

Why people ask about it

IGF-1 LR3 is discussed in bodybuilding and performance communities because IGF-1 signalling is genuinely linked to muscle growth in biology, and the analogue's extended activity is marketed as a way to prolong that signal. This interest sits far ahead of any safety evaluation for human use, and it conflates a laboratory reagent with a therapeutic candidate. It is important for patients to understand that the same growth-promoting biology that makes IGF-1 interesting is also what makes unsupervised use of a long-acting analogue genuinely concerning.

Proposed mechanism

IGF-1 signals through the IGF-1 receptor to activate pathways that promote cell growth, protein synthesis, and, in muscle tissue models, hypertrophy. The LR3 modification is designed to blunt binding to IGF-binding proteins, which normally limit and buffer IGF-1 activity in circulation, so the analogue produces a more sustained and less regulated growth-signalling exposure than the body's own tightly controlled IGF-1 system. This is a mechanistic description drawn from cell and receptor biology, not a demonstration that sustained, poorly buffered growth signalling is safe or beneficial in a person.

What researchers have studied

IGF-1 receptor binding kinetics and resistance to IGF-binding protein sequestration in vitro
Use as a cell-culture supplement to promote proliferation in laboratory assays
General IGF-1 axis biology in growth and metabolic research, separate from this specific analogue
Basic pharmacology characterization in early animal experiments

Human evidence

No published controlled human trials of IGF-1 LR3 administration were identified.
It was not developed as a drug candidate and has not gone through a human safety evaluation pathway.
Broader IGF-1 axis literature in humans documents associations between elevated IGF-1 signalling and cancer risk, which is directly relevant context but is not the same as a study of this analogue itself.
There is no human data on appropriate exposure, clearance, or reversibility of effects for this specific molecule.

Preclinical evidence

In vitro studies confirm prolonged IGF-1 receptor activation with LR3 modification compared to native IGF-1 (cell work).
Cell-proliferation assays show sustained growth signalling consistent with reduced binding-protein regulation (cell work).
Limited animal pharmacology data describe basic distribution and activity, largely in the context of characterizing the reagent rather than testing it as a therapy (animal work).

What is not yet known

Whether IGF-1 LR3 given to a person would meaningfully or safely increase muscle mass, given no human trial exists.
What exposure level would be tolerable, since no formal dose-finding study has ever been conducted.
The magnitude of oncologic risk this specific analogue would carry in a person, beyond general concerns raised by IGF-1 axis biology.
How reliably hypoglycemia could be predicted or managed outside a monitored clinical setting.
Purity, correct identity, and sterility of material sold outside legitimate laboratory-reagent supply chains.
Long-term consequences of unregulated growth factor exposure on tissue growth generally.

Regulatory status and access

IGF-1 LR3 is not compounded, dispensed, or recommended by GOAL.MD, and it is not a substance for which compounding could be considered a form of approval. Ask about current availability. Only a physician can evaluate an individual's health history, and no physician evaluation changes the fact that this material lacks a human safety record.

Known and potential risks

Hypoglycemia is a recognized and serious concern with IGF-1 pathway activation and can occur unpredictably outside a monitored setting.
Elevated or poorly regulated IGF-1 signalling is associated in the broader scientific literature with increased cancer cell proliferation risk, a concern directly relevant to a molecule engineered for prolonged activity.
Because it is sold as an unregulated research reagent, there is no verification of purity, correct identity, dose accuracy, or sterility.
No physician-monitored safety data exist to identify or manage adverse reactions.
Unsupervised use removes any ability to detect early signs of tumor-promoting or metabolic harm.
Legal status of marketing this reagent for human use varies and does not reflect any safety determination.

Cautions and who may not be a candidate

Any personal or family history of malignancy, given the direct relevance of growth factor signalling to cancer biology.
Diabetes or any condition predisposing to hypoglycemia, given the recognized blood sugar risk of IGF-1 pathway activation.
Pregnancy and breastfeeding, given the complete absence of human safety data.
Undiagnosed masses, growths, or abnormal cell findings, which require diagnostic evaluation, not an unproven growth factor analogue.
Children and adolescents, given active growth plates and the seriousness of unregulated growth-signalling exposure.
Use alongside insulin or other glucose-lowering medications without physician supervision.

Questions to discuss with a physician

Given the oncologic concerns tied to IGF-1 signalling, how would you assess my personal risk profile?
What monitoring would even be possible for hypoglycemia risk outside a clinical trial setting?
Why is IGF-1 LR3 different from an approved growth hormone or IGF-1 therapy?
What are the established, evidence-based options for the muscle or growth-related goal I'm asking about?
How would you evaluate any mass or abnormal growth finding before considering growth factor signalling at all?
What does it mean that this was designed as a laboratory reagent rather than a drug candidate?

Frequently asked questions

Is IGF-1 LR3 FDA-approved?

No. It is not an FDA-approved drug product and has no approved indication. It was designed and remains classified as a laboratory research reagent, not a candidate that has gone through human drug development.

Is IGF-1 LR3 the same as IGF-1 used in approved medicines?

No. It is a modified analogue engineered for laboratory use, with changes specifically intended to prolong activity in cell assays. It has not been evaluated as a human therapeutic and should not be equated with any approved product.

Does GOAL.MD sell or recommend IGF-1 LR3?

No. This page is educational only and does not represent an offer, prescription, or endorsement of any kind.

Why is IGF-1 LR3 considered risky?

It engages growth factor signalling that is linked in the broader scientific literature to cancer cell proliferation risk and to hypoglycemia, both serious concerns that have not been studied or managed in any human trial of this specific analogue.

Has IGF-1 LR3 been tested in humans at all?

No published controlled human trials were identified. It was developed as a cell-culture research tool, not as a drug candidate moving toward human testing.

Can IGF-1 LR3 build muscle?

Growth-promoting effects have been shown in cell-culture assays, but there is no human clinical evidence that it safely or effectively builds muscle in people, and the associated oncologic and metabolic risks are significant.

Is it safe to buy IGF-1 LR3 online?

No. It is sold as an unregulated research chemical with no verification of purity, identity, or sterility, and it carries real, well-documented biological risks tied to growth factor signalling.

How is IGF-1 LR3 different from growth hormone secretagogue peptides discussed elsewhere on this site?

Growth hormone secretagogues work upstream by influencing the body's own regulated hormone release, while IGF-1 LR3 is a direct, engineered growth factor analogue with reduced natural regulation, which is a materially different and higher-risk category of exposure.

Who should evaluate any concern related to growth hormone or IGF-1 levels?

A licensed physician, using standard diagnostic testing and evaluation, is the appropriate path, rather than self-directed use of an unregulated growth factor analogue.

What would need to happen before IGF-1 LR3 could be considered for any human use?

It would need to go through formal preclinical toxicology and controlled human trials establishing safety, which has not occurred and is not expected given its origin as a laboratory reagent.

This page is educational. Nothing here can be ordered, and nothing here is a prescription or medical advice. Compounded preparations are not FDA-approved. To ask about current availability, visit goal.md/peptides/connect or call or text 314-907-3103.

Medically reviewed by Michael Fitch, MD, MD. Last reviewed 2026-08-13.