At a glance
Effects
- Muscle hypertrophy & hyperplasia: Activates satellite cells and mTOR signalling to drive new muscle fibre formation (hyperplasia) and enlargement (hypertrophy), effects not typically seen together with conventional anabolics [1][4].
- Accelerated recovery: Upregulates mRNA translation into muscle proteins post-stress, and increases mesenchymal stem cell proliferative potential, shortening repair timelines after intense training [1][5].
- Fat utilisation / body recomposition: Partially inhibits glucose uptake into cells, shifting fuel use towards stored fat; in muscle tissue it also enhances insulin sensitivity for nutrient partitioning [2][3].
- Anti-catabolism / muscle preservation: May block muscle proteolysis (protein breakdown), helping preserve lean tissue during caloric deficits or illness [5].
- Bone & connective tissue support: IGF-1R is expressed in bone and connective tissue; sustained signalling supports bone density and collagen turnover, relevant in recovery from injury [1].
Synthetic peptide hormone / IGF-1 analogue
~20–30 hours (in vitro / model data; no validated human PK trial) [6]
Subcutaneous or intramuscular injection [9]
Not FDA-approved for human use; WADA S2 banned at all times [3][13]
Micrograms (mcg) — not milligrams [8]
About IGF-1 LR3
Every point here is drawn from public medical and harm-reduction sources. A bracketed number after a claim — like [1]— is a reference: tap it to open the exact source it's based on (numbered list at the bottom). It is not a rating or score. Educational information, not medical advice.
Product specifics
- Est. delivery
- 3–7 business days · EU tracked
Product details as stated by the vendor (claims, not independently verified). Delivery is our standard EU estimate.
What it is
IGF-1 LR3 (Long Arg3 Insulin-like Growth Factor-1) is a synthetic, 83-amino-acid analogue of the naturally occurring peptide hormone IGF-1, engineered for enhanced potency and a dramatically extended half-life compared to native IGF-1 [1][2]. It is used in research settings and, off-label, for muscle hypertrophy, accelerated recovery, and body recomposition; it carries no FDA approval for human use [3].
How it works
IGF-1 LR3 binds the IGF-1 receptor (IGF-1R), a transmembrane tyrosine kinase, triggering two major intracellular cascades: the PI3K/Akt/mTOR pathway (driving protein synthesis and cellular hypertrophy) and the MAPK/ERK pathway (stimulating cell proliferation and differentiation) [1][4]. Two structural modifications—an arginine substitution at position 3 and a 13-amino-acid N-terminal extension—reduce its affinity for IGF-binding proteins (IGFBPs) by approximately 1000-fold, meaning far more of the peptide remains free and bioactive in circulation compared to native IGF-1 [2][5]. The result is approximately three times the potency of native IGF-1 and a half-life of roughly 20–30 hours versus minutes for unbound endogenous IGF-1 [6]. In skeletal muscle it activates satellite cells, promotes their differentiation into mature fibres, and drives both hypertrophy and genuine fibre hyperplasia [4].
Risks & side effects
Most important: Because IGF-1 LR3 exerts insulin-like effects on glucose transport, it can precipitate hypoglycemia—including severe episodes requiring assistance or causing seizures, as documented in the closest clinical dataset (Increlex/mecasermin), where 42% of subjects experienced hypoglycemic events and four had hypoglycemic seizures or loss of consciousness [7]. Compounding this, its 20–30 hour half-life means any metabolic disruption is prolonged and less easily corrected than with short-acting compounds [6][8].
Common
- Hypoglycemia (low blood sugar) — the most frequently reported adverse event; risk is highest when dosed away from meals or with concurrent insulin use [7][8].
- Injection-site reactions (redness, swelling, bruising) with subcutaneous or intramuscular administration [9].
- Joint pain and peripheral oedema / mild water retention due to sodium retention effects [9][10].
- Headaches and nausea, particularly early in use or at higher doses [2].
- Receptor desensitisation with daily use — downregulation of IGF-1R reduces anabolic response while maintaining side-effect exposure [4][8].
Serious
- Acromegaly-like features with prolonged supraphysiological exposure: jaw enlargement (prognathism), hand/foot growth, soft-tissue thickening, cardiomegaly, hepatomegaly — dose- and duration-dependent [10][11].
- Insulin resistance / impaired glucose regulation with chronic use; the extended half-life amplifies this risk relative to native IGF-1 [8].
- Tumour promotion — IGF-1R signalling is a well-established growth driver for multiple cancers; elevated IGF-1 is epidemiologically linked to colorectal, breast, and prostate cancer risk; use is contraindicated in anyone with cancer history [10][12].
- Severe hypoglycemia requiring emergency intervention, especially when co-administered with insulin or at high doses [7][9].
Rare
- Intestinal mucosal hypertrophy (gut growth) reported in early studies — an organomegaly effect of broad IGF-1R activation [2].
- Tonsillar hypertrophy and lymphoid tissue swelling, observed in mecasermin (native IGF-1) clinical programme [11].
- Growth-plate interference in individuals under ~25 years of age — IGF-1 signalling can affect bone maturation [12].
Safety & harm reduction
- Active or prior malignancy — IGF-1R activation drives tumour cell proliferation; use is strictly contraindicated [10][12].
- Diagnosed diabetes or pre-diabetes — severe hypoglycemia risk is significantly elevated [12].
- Concurrent exogenous insulin use without expert medical oversight — additive glucose-lowering creates life-threatening hypoglycemia risk [12].
- Pregnancy or breastfeeding — no safety data; fetal/infant harm cannot be excluded [12].
- Under age ~25 — IGF-1 signalling can affect growth-plate closure and organ development [12].
- Competitive athletes subject to drug testing — WADA S2 prohibition, banned in and out of competition; detection assays are published [13][3].
- Blood glucose before and after each injection — hypoglycemia may be delayed and asymptomatic initially [7][9].
- Serum IGF-1 levels to assess systemic exposure and avoid supraphysiological accumulation [8].
- Fasting insulin and HbA1c with extended use to detect emerging insulin resistance [8].
- Cardiovascular assessment (echocardiogram) for anyone using long-term or at higher doses — cardiomegaly risk [10].
- Cycle duration: most protocols cap continuous use at 4–6 weeks with at least an equal off-period to limit receptor downregulation and cumulative side-effects [8].
- Exogenous insulin — additive hypoglycaemic effect; combination requires medical supervision and is high-risk [12].
- Other IGF-1 isoforms (e.g. native IGF-1, IGF-1 DES) — combining with LR3 offers no additive benefit and risks receptor saturation and insulin sensitivity impairment [14].
- Growth hormone (GH) — concurrent use amplifies systemic IGF-1 signalling and cumulative risks including organomegaly [10].
- Hypoglycaemic agents / sulfonylureas / GLP-1 agonists — additive blood-glucose lowering; use extreme caution [9].
- Always reconstitute lyophilised powder with bacteriostatic water (BAC water); inspect for particulates before use [8].
- Time injection post-workout with a meal present — elevated blood glucose and available carbohydrates reduce hypoglycemia risk [7].
- Avoid pre-sleep dosing — nocturnal hypoglycemia is harder to detect [7].
- Keep fast-acting glucose (glucose tablets, juice) on hand for every injection session [9].
- Do not use daily without cycling — receptor downregulation develops quickly; standard protocol is 4–6 weeks on, equal time off [8].
- Start at the lowest reported dose (10–20 mcg) to assess individual glucose response before any escalation [8].
Dosage context
No human clinical trial has validated a dosing range specifically for IGF-1 LR3 [7]. Community-reported ranges, which are observational and not clinical guidance, fall between 20–50 mcg/day subcutaneously for general use, with some advanced protocols reaching 80–100 mcg/day — a range where hypoglycaemia risk rises substantially [8][9]. Women are typically advised toward the lower end (10–20 mcg/day) [8]. The compound is measured in micrograms, not milligrams; syringe accuracy is critical [8]. Most reported protocols cap cycles at 4–6 weeks with at least an equal off-period [8].
Sources
- 1.The Peptide University — IGF-1 LR3: Properties, Mechanisms, and Applications
- 2.Wikipedia — IGF-1 LR3
- 3.Swolverine — Side Effects of IGF-1 Peptides
- 4.Pinnacle Peptides — IGF-1 LR3 Receptor Activation Research
- 5.MediSearch — IGF-1 LR3 Explained
- 6.Wikipedia — IGF-1 LR3 (half-life)
- 7.Peptide Dosing Protocols — IGF-1 LR3 Guide (Increlex/mecasermin clinical data)
- 8.PeptideDeck — IGF-1 LR3 Dosage, Cycle Length & Side Effects
- 9.ChemicalBook — Mechanism and Side Effects of IGF-1 LR3
- 10.Peptides Institute — IGF-1 LR3 Research Profile
- 11.Peptide Protocol Wiki — IGF-1 LR3 Side Effects and Safety Profile
- 12.PeptidesExplorer — IGF-1 LR3 Benefits, Dosage & Side Effects
- 13.Real Peptides — IGF-1 LR3 Legal & Regulatory Status
- 14.Peptide Affect — IGF-1 LR3 Interactions
This information is provided for educational and harm-reduction purposes only. It is not medical advice. These substances can carry serious health risks; effects and safe use vary by individual. Consult a qualified healthcare professional before use. Legal status varies by country — it is your responsibility to know your local law. We do not encourage misuse.