Not medical advice. Talk to your provider before using any peptide.
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IGF-1 LR383 residuesMFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSAEach bubble = one amino acid. Size = residue mass. Color = chemical class.Also known as: Long R3 IGF-1, LR3 IGF-1, IGF-1 Long R3
Regular IGF-1 stays active for about 15 minutes. The LR3 modification stretches that to 20 to 30 hours. IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a recombinant 83-amino acid protein that sidesteps IGF binding proteins almost entirely, leaving most of the circulating compound free and active. That extra exposure time is exactly what makes it both powerful and risky. No human clinical trial has tested LR3 for anabolic endpoints; animal models from Francis et al. [1] confirmed organ growth at sustained high doses. Community evidence across hundreds of threads on r/Peptides and r/steroids points to meaningful lean mass gains within 4 to 6 week cycles at 20 to 50 mcg per day.
Fifteen minutes. That is how long native IGF-1 stays unbound and active in circulation before binding proteins snatch it up. The LR3 variant rewrites that timeline completely. IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1, also called Long R3 IGF-1) is an 83-amino acid recombinant protein with a 13-amino acid N-terminal extension plus an arginine-to-glutamate substitution at position 3. These changes reduce binding protein affinity by over 100-fold (Ballard et al.)[2]. The result is a compound that circulates mostly free with a functional half-life of 20 to 30 hours. IGF-1 sits downstream of growth hormone in the anabolic signaling cascade. GH tells the liver to produce IGF-1; IGF-1 then activates the IGF-1 receptor, triggering the PI3K/Akt/mTOR pathway that drives protein synthesis, satellite cell activation, and muscle cell hyperplasia. LR3 hits those same receptors with 2 to 3 times the potency of native IGF-1 and holds onto them far longer. In practice, most users run 20 to 40 mcg per day subcutaneously for 4 to 6 weeks, followed by 4 to 6 weeks off to restore receptor sensitivity. Community reports across hundreds of r/Peptides and r/steroids threads consistently describe improved recovery, muscle fullness, and lean mass accrual within the first 3 to 4 weeks. The trade-off is real. Hypoglycemia hits if peri-injection nutrition is missed. Francis et al. [1] documented organ enlargement in guinea pigs at 120 mcg per day continuous infusion. A Lancet meta-regression [3] linked raised circulating IGF-1 to increased cancer risk. No human RCT has validated the dosing protocols in community use.
IGF-1 LR3 binds the same type 1 IGF receptor (IGF-1R) as native IGF-1, but it does so with a critical pharmacokinetic advantage. Native IGF-1 is 98% sequestered by six known IGF binding proteins (IGFBPs 1 through 6), which limit free-fraction exposure to roughly 12 to 15 minutes. The LR3 modification drops IGFBP affinity by over 100-fold (Ballard et al.)[2], so most of the injected compound circulates unbound. Once LR3 occupies IGF-1R, it triggers the same intracellular cascade as native IGF-1. Receptor autophosphorylation activates insulin receptor substrate proteins, which recruit PI3K. PI3K generates PIP3, activating Akt. Akt then phosphorylates mTOR, the master regulator of protein synthesis and cell growth. This pathway drives two anabolic processes: hypertrophy (larger muscle fibers through increased protein synthesis) and hyperplasia (new muscle cell formation through satellite cell activation). IGF-1R also mediates GLUT4 translocation to the cell membrane, explaining the hypoglycemia risk. The receptor sits on nearly every tissue type, not just skeletal muscle. Sustained occupancy from a 20 to 30 hour half-life compound means the colon, kidneys, adrenals, and spleen all receive growth signaling alongside muscle. Francis et al. [1] confirmed this in guinea pigs; organ enlargement tracked directly with continuous infusion duration. Receptor downregulation begins after 4 to 6 weeks of daily administration as cells reduce surface IGF-1R density in response to chronic saturation.
Long-acting IGF-1 analog with confirmed anabolic and organ-growth effects in animal models. Cancer proliferation signal reinforced by 2024-2025 literature. No human RCT for anabolic use. Mechanism well-established; clinical dosing entirely extrapolated.
Francis et al. 1995 (PMID 7561636): guinea pig organ growth at 120 mcg/day continuous infusion; Ballard et al. 1996 (PMID 8708565): SC potency preserved with minimal IGFBP binding
No human RCT for muscle hypertrophy or anabolic endpoints. All organ-growth and potency data from animal models (guinea pig, rat). Cancer risk data (PMID 15110491) is epidemiological IGF-1 association, not LR3-specific. Formal human PK study does not exist.
Consistently reported lean mass accrual and improved recovery in 4-6 week cycles. Hypoglycemia and organ growth concerns lower enthusiasm vs. raw anabolic potential. Most respected experienced users treat 20-40 mcg/day as the practical ceiling.
Mechanism and approximate dosing are consistent between science and community. Science focuses on organ growth risk, cancer signal, and lack of human data: risks community underweights. Community reports confirm anabolic effects predicted by receptor biology but no human trial validates the specific dosing protocols in use.
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 20mcg | Daily |
| Moderate | 40mcg | Daily |
| Aggressive | 80mcg | Daily |
Reconstitution math for a 1mg vial: add 1.0 mL bacteriostatic water. That gives you 1,000 mcg per mL. On a U-100 insulin syringe, each unit (tick mark) equals 10 mcg. So 2 IU = 20 mcg (beginner dose), 4 IU = 40 mcg (moderate), 8 IU = 80 mcg (aggressive). One vial at 40 mcg per day lasts 25 days, enough for a full 4-week cycle with one day to spare. At the beginner dose, a single vial covers 50 days. Store reconstituted vials refrigerated at 2 to 8 degrees C. Discard after 28 to 30 days. Never freeze reconstituted solution. The thing most beginners miss: eat within 15 to 30 minutes of injecting. Post-workout timing is popular because you'll be eating anyway. Morning fasted works too, just have food ready before you pin. Get baseline bloodwork (serum IGF-1, fasting glucose, HbA1c) before your first cycle. If your natural IGF-1 is already high-normal or above, adding LR3 on top increases proliferation risk.
Continuous IGF-1R occupancy with a 20-30 hour half-life compound leads to receptor downregulation (reduced surface expression) and desensitization of downstream PI3K/Akt/mTOR signaling. This progressively blunts the anabolic response. Cycling off allows receptor density and sensitivity to recover. Secondary rationale: limiting cumulative organ growth exposure (particularly colonic epithelium, kidneys, adrenals, spleen) that scales with total IGF-1R stimulation load over time.
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Expected: Moderate lean mass support; improved recovery; minimal organ growth risk at 20 mcg/day
Monitor: Baseline serum IGF-1 and fasting glucose before starting. Check fasting glucose weekly during cycle.
Gather supplies: 1mg IGF-1 LR3 lyophilized vial, 1.0 mL bacteriostatic water, U-100 insulin syringe (29 to 31 gauge), alcohol swabs.
Draw 1.0 mL (100 units) of bacteriostatic water into a syringe. Inject slowly down the inside wall of the LR3 vial. Swirl gently until dissolved. Never shake.
For a 20 mcg dose, draw to the 2 IU mark. For 40 mcg, draw to the 4 IU mark. For 80 mcg, draw to the 8 IU mark.
Subcutaneous: pinch abdominal fat or upper thigh, insert needle at a 45-degree angle. Intramuscular: inject into the trained muscle for purported site-enhancement effect. Inject slowly over 5 to 10 seconds.
Eat protein and carbohydrates within 15 to 30 minutes of injection to manage the glucose-lowering effect. Post-workout is the most common timing because nutrition follows naturally.
Cap and refrigerate the reconstituted vial immediately after use. Discard after 28 to 30 days.
Monitor fasting blood glucose daily during the first week, then weekly for the remainder of the cycle. Stop the cycle and consult a physician if fasting glucose drops below 60 mg/dL.
No dose adjustment; systemic bioavailability equivalent to IM for a long-acting compound
Easiest injection; consistent systemic distribution; preferred for full-body anabolic effect
Same dose as SubQ; slightly faster initial absorption but identical half-life
Community uses IM into the trained muscle for purported localized hypertrophy at injection site; this site-enhancement effect is anecdotal and not confirmed in peer-reviewed literature; glucose risk profile is identical to SubQ
Classic GH + LR3 performance stack. GH stimulates endogenous IGF-1 production; exogenous LR3 extends IGF-1R stimulation beyond endogenous pulse. Allows lower GH doses for equivalent anabolic effect.
2-4 IU GH/day + 40-50 mcg LR3/day; run LR3 during GH cycle weeks
GHRH analog runs during LR3 off-weeks to maintain GH axis activity; some advanced users run concurrently at lower LR3 doses (20-30 mcg/day)
CJC-1295 DAC 2 mg/week during LR3 off-cycles; monitor IGF-1 if stacking simultaneously
GHRP complement; stimulates pulsatile GH release which drives endogenous IGF-1; used with LR3 for synergistic GH axis stimulation without insulin-like side effects
200-300 mcg ipamorelin 2-3×/day + 20-40 mcg LR3/day
Recovery stack pairing: BPC-157 provides local tissue repair via VEGF/NO pathways; LR3 adds systemic IGF-1R-mediated growth factor signaling for lean mass preservation during injury recovery
BPC-157 250 mcg 2×/day + LR3 20-30 mcg/day
Both activate IGF-1R: LR3 provides continuous systemic stimulation (20-30h) while DES provides a sharp local pulse (~25 min). Stacking creates additive receptor load, amplifies organ growth risk significantly, and prolongs hypoglycemia window. Treat as mutually exclusive alternatives, not complements.
Do not combineCompounding hypoglycemia risk is extreme. LR3 already lowers blood glucose via IGF-1R-mediated glucose uptake; adding exogenous insulin without expert-level glucose management and continuous glucose monitoring creates life-threatening hypoglycemia risk. Requires clinical expertise, not community-level self-administration.
Do not combinePricing updated 2026-04-09
Hypoglycemia is the most immediate safety concern with IGF-1 LR3. The compound activates GLUT4 translocation through IGF-1R, pulling glucose from the bloodstream into cells. Miss your peri-injection meal and blood sugar can drop fast. Symptoms include tremor, confusion, sweating, and dizziness. This is not a maybe-someday risk; community reports treat it as a certainty during the first week if nutrition timing is off. Keep 15 to 20 grams of fast-acting carbohydrates (glucose tablets, juice) within reach at every injection. Organ growth is the concern that keeps experienced users conservative on dosing. IGF-1 receptors exist on virtually every tissue. LR3's extended half-life means 20 to 30 hours of continuous receptor stimulation per injection, hitting the colon, kidneys, adrenals, and spleen alongside skeletal muscle. Francis et al. [1] documented significant organ enlargement in guinea pigs receiving 120 mcg per day by continuous infusion. At 20 to 40 mcg per day in short cycles, this risk is low. At 80 mcg per day or stacked with other growth-promoting compounds, it climbs. Cancer proliferation is a legitimate concern backed by epidemiological data. A Lancet meta-regression of 3,609 cases [3] found raised circulating IGF-1 associated with increased risk of prostate, colorectal, and premenopausal breast cancer. This data reflects endogenous IGF-1 levels, not exogenous LR3 specifically, but the mechanism of action is the same receptor. Active malignancy or cancer history is a hard contraindication. Water retention and joint discomfort are common during weeks 1 through 3. Sodium retention drives mild edema in the hands and face. Most users report this stabilizes or becomes manageable by mid-cycle. Receptor desensitization occurs if cycles run beyond 6 weeks. Anabolic response fades as cells downregulate surface IGF-1R density. Increasing the dose to compensate makes the organ growth and hypoglycemia profile worse without restoring efficacy. The correct response is to stop and allow 4 to 6 weeks off for receptor recovery. Product quality variance adds a layer of risk unique to research-grade compounds. LR3 is an 83-amino acid recombinant protein requiring bacterial expression systems to manufacture. Anti-doping labs and community testing consistently document counterfeits and underdosed vials in the grey market. A blunted response at expected doses may indicate a bad product, not a dosing problem. When to stop: fasting glucose below 60 mg/dL, persistent joint pain, visible soft-tissue swelling, or signs of rapid visceral enlargement. When to see a doctor: any hypoglycemic episode involving confusion or loss of consciousness, unexplained abdominal distension, or new lumps or masses anywhere in the body. Contraindications: active or prior malignancy, pregnancy or breastfeeding, type 1 or poorly controlled type 2 diabetes, individuals under 18 or with open growth plates, known hypersensitivity to IGF-1, and active acromegaly or raised baseline IGF-1.
Verify IGF-1 LR3 dosing and safety with a second opinion
IGF-1 LR3 is an 83-amino acid recombinant protein requiring bacterial or mammalian cell expression systems for synthesis. High manufacturing complexity creates significant grey-market quality variance. Community and anti-doping labs consistently document counterfeits and underdosed vials. No regulatory oversight or mandatory purity/sterility standards apply to research-use products.
| Test | When | Target |
|---|---|---|
| Serum IGF-1 | Baseline before cycle; optional mid-cycle (week 2-3) | Baseline: within lab reference range; mid-cycle: not exceeding ~300 ng/mL (upper normal) |
| Fasting glucose | Baseline pre-cycle; daily during first week; weekly thereafter | 70-100 mg/dL fasting; concern if <60 mg/dL |
| HbA1c | Baseline pre-cycle | <5.7% (normal); >6.5% = relative contraindication |
| Comprehensive metabolic panel (CMP) | Baseline; end of cycle if >4 weeks or stacked with GH | Within normal reference ranges |
Elevated baseline IGF-1 is a contraindication; mid-cycle check confirms LR3 is exerting expected effect and serum IGF-1 is not supraphysiologically elevated
IGF-1R activation drives GLUT4-mediated glucose uptake; hypoglycemia is the most common acute adverse effect
Identifies pre-existing glucose regulation issues that markedly increase hypoglycemia risk
Kidney and liver function monitoring; prolonged IGF-1R stimulation at higher doses can drive renal enlargement
Initial blood glucose fluctuations may occur. Mild pump sensation in trained muscles reported anecdotally. No visible body composition changes yet.
Increased muscle fullness and pumps during training. Water retention possible. Appetite may increase. Monitor blood sugar around dosing.
Noticeable improvements in recovery between sessions. Early lean mass gains become apparent. Localized muscle growth at injection sites reported in IM protocols.
Peak lean mass accrual and recovery benefits. Cycle off after 4-6 weeks to maintain IGF-1R sensitivity. Fat reduction may accompany lean tissue gains.
Days 1 through 3 (Acclimation): IGF-1R occupancy begins within 1 to 2 hours of the first injection. Blood glucose fluctuations are common, especially when injecting fasted. Some users notice a mild pump sensation in trained muscles. Nothing visible changes in body composition this early. Keep fast-acting carbs nearby; hypoglycemia symptoms hit hardest before your nutrition timing locks in. Weeks 1 through 2 (Early Response): Muscle fullness and pumps during training pick up noticeably. Water retention may show in the face and hands. Appetite tends to increase as the metabolic demand rises. The PI3K/Akt/mTOR pathway is actively upregulating protein synthesis at this point. Blood glucose management gets easier as you dial in meal timing around injections. Weeks 3 through 4 (Peak Response): This is when the cycle earns its reputation. Recovery between sessions improves enough that most users notice it without looking for it. Early lean mass gains become visible, particularly for those in caloric surplus. Users running IM protocols into trained muscles report localized growth at injection sites, though this remains anecdotal. Hypoglycemia episodes typically decrease as peri-injection nutrition becomes routine. Animal data from Hizuka et al. [4] confirms lean mass accrual peaks in this window. Weeks 5 through 6 (Late Cycle): Peak lean mass and recovery benefits. Fat reduction sometimes accompanies lean tissue gains. Response may plateau compared to weeks 3 through 4 as IGF-1R begins downregulating from continuous saturation. Most experienced users cap their cycle here. Extending beyond 6 weeks increases cumulative organ growth exposure without proportional benefit. Off-cycle, weeks 1 through 6 post: Muscle fullness drops slightly as water retention resolves. Strength and lean mass gains are generally retained with adequate nutrition. IGF-1R density recovers over 4 to 6 weeks. Check serum IGF-1 before restarting; if levels remain above 250 ng/mL at the 4-week mark, extend the off-cycle.
IGF-1R occupancy begins within 1-2 hours. Glucose lowering effect (IGF-1R-mediated GLUT4 translocation) starts immediately. No tissue changes visible this early.
Mild pump sensation in trained muscles. Blood glucose fluctuations common, especially if injecting fasted. No visible body composition changes.
Upregulated protein synthesis via IGF-1R → PI3K/Akt/mTOR pathway. Mild fluid retention from sodium retention. Appetite increase from metabolic demand.
Increased muscle fullness and pumps during training. Water retention (faces/hands). Appetite increase. Monitor blood glucose diligently.
Sustained IGF-1R stimulation drives myosatellite cell activation and protein anabolism. Animal data (PMID 8219484) shows lean mass accrual peaks in this window.
Noticeable recovery improvement between sessions. Early lean mass gains visible. Localized muscle growth at IM injection sites reported anecdotally. Hypoglycemia incidents less frequent as users adapt nutrition timing.
IGF-1R downregulation begins with continuous saturation. Cumulative organ growth exposure increases. No additional tissue studies beyond 6-week window in relevant animal models.
Peak lean mass accrual and recovery benefits. Fat reduction may accompany lean gains. Response may plateau vs. weeks 3-4. Most experienced users cap cycle here.
IGF-1R density recovers after agonist removal. Lean mass gains are generally maintained if nutrition is adequate. IGF-1 levels return toward baseline.
Muscle fullness diminishes slightly as water retention resolves. Strength and lean mass largely retained. Sensitivity restored after 4-6 weeks off.
Source: Estimated 20-30h based on reduced IGFBP affinity vs native IGF-1 (t½ ~12-15h); Francis et al. 1995 PMID 7561636, Ballard et al. 1996 PMID 8708565
Loading the interactive decay curve.
IGF-1 LR3 is classified as a research chemical in the United States. It is not FDA-approved for human use and is sold labeled "for research purposes only" or "not for human consumption." No pharmaceutical-grade formulation exists for prescription or clinical use. The World Anti-Doping Agency (WADA) prohibits IGF-1 and all its analogs, including LR3, at all times both in and out of competition. Athletes subject to drug testing face sanctions for any detected use. Purchasing LR3 for personal research use is legal in the US at the time of writing. Compounding pharmacies do not produce IGF-1 LR3; it is only available through research peptide vendors. Quality variance is high; request third-party HPLC and mass spectrometry certificates of analysis before purchasing. This content is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Consult a qualified healthcare provider before using any research compound.
Peptide Schedule Research TeamReviewed Apr 20267 Citations
