IGF-1 LR3
A supercharged version of your body's own growth factor that stays active 2-3 times longer than regular IGF-1, making it a powerhouse for muscle growth, recovery, and cellular regeneration.
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team
Typical dose
20–100 mcg
Compound profile
Scientific & efficacy data
Growth Hormone
Peptide profile
Strong preclinical
IGF-1 LR3
20–100 mcg · Once daily
Molecular formula
C400H625N111O115S9
- Mol. weight
- 9111.4 g/mol
- CAS number
- 946870-92-4
- PubChem
- Not assigned
- Developed · 1987
- Francis John Ballard and colleagues
CSIRO Division of Human Nutrition, Adelaide, Australia
Amino acid sequence
MFPAMPLSSL FVNGPRTLCG AELVDALQFV CGDRGFYFNK PTGYGSSSRR APQTGIVDEC CFRSCDLRRL EMYCAPLKPA KSA (83 amino acids with Arg3 substitution and 13 amino acid N-terminal extension)Muscle Growth
One of the most potent peptides for muscle building through both hypertrophy and hyperplasia mechanisms
Recovery Speed
Significantly accelerates post-workout recovery and tissue repair, allowing more frequent intense training
Nutrient Utilization
Enhances how efficiently your body uses protein and carbohydrates for muscle building versus fat storage
Dosing
How much do I take?
Covers timing · dose-adjustment guidance.
Suitability
Is this right for me?
Best for muscle growth and hypertrophy & post-workout recovery
Best for
Serious Muscle Builders
If you're pushing hard in the gym and want to maximize every rep, IGF-1 LR3 helps your muscles grow through both hypertrophy (bigger cells) AND hyperplasia (more cells) [2]. That's a one-two punch that few other compounds offer.
Recovery-Focused Athletes
Train hard, recover faster. IGF-1 LR3 accelerates tissue repair and reduces the time you need between intense sessions [14]. It's particularly valuable during high-volume training blocks or when preparing for competition.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare IGF-1 LR3 with similar peptides to find the best fit for your goals.
Administration
How do I use it?
Subcutaneous injection · Intramuscular injection
Route
Subcutaneous injection (under the skin) is most common; intramuscular injection into specific muscles is also used for localized effects
Best sites
Covers reconstitution · step-by-step technique · storage · a sample daily schedule.
Safety
Is it safe?
4 common side effects · 2 serious
IGF-1 LR3 has been extensively studied in research settings and shows a predictable side effect profile when used responsibly.
The primary concern is hypoglycemia, which is manageable with proper nutrition timing [7][9]. Long-term safety data in humans is limited since it's used as a research compound. Joint discomfort and water retention are generally mild and resolve when cycling off.
Most safety data comes from animal studies and limited human research contexts. While these suggest a favorable profile at moderate doses, large-scale human clinical trials haven't been conducted. Always work with a healthcare provider familiar with peptide research when using any research compound.
Common side effects · experienced by some users
Hypoglycemia (low blood sugar)
This is the most important side effect to understand. IGF-1 LR3 acts like insulin and drives glucose into cells, which can leave you feeling shaky, dizzy, or weak [7][8].
Management: Always eat within 30 minutes of injection. Keep fast-acting carbs (juice, glucose tablets) nearby. Learn your body's warning signs: shakiness, sweating, hunger, confusion.
Injection site reactions
Redness, slight swelling, or itching at the injection site is normal and usually fades within a day.
Management: Rotate injection sites regularly. Use proper sterile technique. A cool compress can help if irritation occurs.
Water retention
Some puffiness or bloating, especially in hands and face, as IGF-1 causes cells to hold more water [16].
Management: Usually mild and temporary. Moderate sodium intake, stay well-hydrated, and it typically resolves as your body adjusts or when you cycle off.
Headaches
Particularly common in the first week as your body adjusts to the peptide.
Management: Stay hydrated, don't skip meals, and the headaches usually subside after the first week. If persistent, consider reducing dose.
Less common
These typically resolve with continued use or dose adjustment.
Stop and seek help if
- Any severe hypoglycemic episode that doesn't resolve quickly with food
- Persistent numbness, tingling, or carpal tunnel symptoms
- Joint pain that interferes with training or daily activities
- Signs of allergic reaction (rash, swelling, difficulty breathing)
- Any concerning or unusual symptoms that worry you
- Completion of your planned cycle (typically 4-6 weeks)
IGF-1 LR3 is a research compound, not approved for human therapeutic use by the FDA. This information is for educational purposes only and not medical advice. Always consult with a healthcare provider before starting, stopping, or modifying any research protocol.
With other peptides
- Safe:MGF (Mechano Growth Factor) — Potentially synergistic for muscle growth. MGF works locally while IGF-1 LR3 works systemically. Can be used together with careful timing.
- Safe:CJC-1295 — Can be stacked for complementary effects—CJC increases natural GH release while IGF-1 LR3 provides direct IGF effects. Space injections apart.
- Safe:GHRP-6 — Safe to combine. GHRP-6 stimulates hunger which can actually help prevent hypoglycemia from IGF-1 LR3.
- Caution:Insulin — DANGEROUS combination. Both lower blood sugar dramatically. Severe hypoglycemia risk. Do NOT combine unless under strict medical supervision.
With medications
- Caution:Diabetes medications (Metformin, Sulfonylureas) — Increased hypoglycemia risk. Blood sugar-lowering effects compound dangerously. Requires medical supervision and dose adjustments.
- Caution:Insulin (medical) — Extremely dangerous combination. Both dramatically lower blood sugar. Can cause severe, life-threatening hypoglycemia.
- Safe:Blood thinners (Warfarin, etc.) — May increase bruising at injection sites. Not dangerous but worth monitoring.
- Caution:Beta-blockers — Can mask hypoglycemia symptoms (shakiness, rapid heartbeat), making low blood sugar harder to detect. Use with caution.
With supplements
- Safe:Creatine — Safe and potentially complementary. Both support muscle cell function and recovery.
- Safe:Protein supplements — Highly recommended! Adequate protein maximizes IGF-1 LR3 benefits. Take protein with or shortly after injection.
- Safe:Chromium — May enhance insulin sensitivity, potentially increasing hypoglycemia risk. Monitor blood sugar more carefully.
- Safe:Alpha-Lipoic Acid (ALA) — Can increase glucose uptake, compounding hypoglycemia risk. Use lower doses of both if combining.
Effectiveness
How do I know it's working?
Strong preclinical · first signs week 1
Evidence level
Strong preclinical
(extensive animal studies)
Regulatory status
Research compound
Onset of effects
Rapid
(hours to days)
How it works
Think of IGF-1 as your body's building signal—it tells cells to grow, repair, and multiply.
Regular IGF-1 gets grabbed by binding proteins almost immediately, like trying to deliver a package but everyone keeps intercepting it [3]. IGF-1 LR3 is modified so those binding proteins can't hold onto it [1]. The result?
It circulates freely instead of being bound and inactivated within minutes, actually reaching your muscles and telling them to grow.
Plus, unlike most growth factors that only make cells bigger, IGF-1 can trigger the creation of entirely new muscle cells—that's hyperplasia, and it's the holy grail of muscle building [2].
The deeper mechanism
IGF-1 LR3 (Long Arginine 3-IGF-1) is a modified 83-amino acid analog of human IGF-1. The key modifications include a 13-amino acid extension at the N-terminus and substitution of Arg for Glu at position 3.
These changes reduce binding affinity for IGF binding proteins (IGFBPs) by approximately 1000-fold, dramatically increasing the fraction that circulates free and biologically active [6].
IGF-1 LR3 binds the Type 1 IGF receptor (IGF-1R) with somewhat lower (about 3-fold) affinity than native IGF-1 [17], activating downstream PI3K/Akt and Ras/MAPK/ERK signaling cascades [2].
The PI3K/Akt pathway promotes protein synthesis via mTOR activation and inhibits protein degradation through FOXO transcription factor suppression [11][12]. The ERK pathway mediates proliferative effects [2].
Unlike most anabolic agents that primarily induce hypertrophy (cell enlargement), IGF-1 uniquely promotes satellite cell activation and hyperplasia (new muscle fiber formation) [2][13].
Its insulin-like activity at supraphysiological concentrations accounts for hypoglycemia risk through glucose transporter (GLUT4) translocation and enhanced cellular glucose uptake [7][8].
What to expect
Week 1
What you might notice
- Increased muscle fullness and pumps during workouts
- Possible hypoglycemia symptoms as you learn dosing/eating timing
- Mild headaches as your body adjusts
- Perhaps some water retention (slight puffiness)
- Improved workout recovery already beginning
What's normal
- Needing to eat more frequently to prevent low blood sugar
- Some initial side effects that should diminish
- Your muscles looking and feeling fuller
What's next
- Continue dialing in your nutrition timing
- Keep carbs accessible for hypoglycemia prevention
- Maintain consistent injection schedule
Week 2-3
What you might notice
- Noticeable improvements in workout recovery speed
- Muscle gains becoming more apparent
- Side effects typically stabilizing or diminishing
- Better nutrient partitioning—muscles look fuller, potentially leaner
- Improved strength and training capacity
What's normal
- Settling into a routine with injection and eating timing
- Continued muscle fullness and improved pumps
- Energy levels stabilizing
What's next
- Maintain consistent protocol
- Consider slight dose adjustment if needed
- Continue tracking progress and any side effects
Week 4-6
What you might notice
- Peak effects—maximum muscle growth and recovery benefits
- Measurable gains in muscle size and strength
- Body composition improvements (more muscle, potentially less fat)
- Excellent workout recovery
- Possible receptor downregulation if extended beyond 6 weeks
What's normal
- Best results typically seen during this period
- Stable side effect profile
- Feeling strong and recovered
What's next
- Complete cycle at 4-6 weeks
- Begin planning off-cycle period (4+ weeks)
- Maintain training intensity to preserve gains
Post-cycle (off period)
What you might notice
- Gradual return to baseline muscle fullness
- Maintained muscle gains if training and nutrition stay consistent
- No withdrawal effects—you simply stop
- Side effects resolve completely within days
What's normal
- Slight reduction in muscle pump and fullness
- Return of normal blood sugar patterns
- Maintained strength and most muscle gains
What's next
- Continue solid training and nutrition
- Take at least 4 weeks off to reset receptors
- Plan next cycle if desired
Signs it's working
Muscle Growth Indicators
- Increased muscle fullness and pump during training
- Visible improvements in muscle size within 2-3 weeks
- Clothes fitting tighter in the chest, arms, and shoulders
- Improved vascularity when lean
- Strength gains in major lifts
Recovery Indicators
- Less muscle soreness after intense training
- Ability to train more frequently without overtraining
- Faster return to peak performance between sessions
- Reduced fatigue during high-volume training blocks
Body Composition Indicators
- Improved muscle-to-fat ratio
- More defined muscle separation
- Better nutrient partitioning (muscles seem to absorb food better)
- Maintained or reduced body fat despite calorie surplus
Not seeing results? Common reasons
- Blood sugar management issues—if you're constantly hypoglycemic, you may not be eating enough around injections, limiting results
- Peptide degradation—improper storage is a common culprit; always check solution clarity and storage conditions
- Dose too low—starting doses are conservative; you may need to increase after assessing tolerance
- Poor quality product—only purchase from verified sources with third-party testing certificates (COAs)
- Insufficient training stimulus—IGF-1 LR3 enhances your body's response to training, but you still need to train hard
- Inadequate nutrition—not enough protein or calories limits the peptide's ability to build muscle
Key research
Questions
Frequently asked
What's the difference between IGF-1 LR3 and regular IGF-1?
Regular IGF-1 gets grabbed by binding proteins within minutes and quickly becomes inactive. IGF-1 LR3 has been modified so those binding proteins can't hold onto it, leaving it free and biologically active rather than bound and inactivated within minutes. This means it actually reaches your muscles and stays active long enough to do its job [1][3].
Why do I need to eat when using IGF-1 LR3?
IGF-1 LR3 works similarly to insulin—it drives nutrients (including glucose) into your cells [7][8]. If you don't have enough glucose in your blood, you'll experience hypoglycemia: shakiness, dizziness, confusion, or worse. Always eat a meal with protein and carbs within 30 minutes of your injection.
Can I inject IGF-1 LR3 directly into specific muscles for localized growth?
Yes, many users inject intramuscularly into target muscles hoping for site-specific enhancement. However, IGF-1 LR3 circulates systemically regardless of injection site. Local injections may provide some preferential local effects, but the peptide will benefit your whole body, not just one muscle.
How long should I cycle IGF-1 LR3?
Most protocols run 4-6 weeks on, followed by at least 4 weeks off. This allows IGF-1 receptors to resensitize. Running too long without breaks can lead to receptor downregulation, diminishing returns, and increased side effect risk. Some users do 5 days on, 2 days off throughout their cycle.
Is IGF-1 LR3 the same as HGH?
No, they're different but related. Human Growth Hormone (HGH) stimulates your liver to produce IGF-1, which then causes many of HGH's effects [10]. IGF-1 LR3 bypasses this step—you're getting the active growth factor directly. Some users stack both for complementary effects, though this requires careful timing.
Will IGF-1 LR3 cause cancer?
IGF-1 is a growth factor that can stimulate cell division, which is concerning for anyone with existing cancer or pre-cancerous conditions [2][5]. However, there's no evidence that IGF-1 LR3 causes cancer in healthy individuals at typical doses. If you have any history of cancer or strong family history, discuss with an oncologist before using any growth-promoting compound.
Can I use IGF-1 LR3 for fat loss?
While IGF-1 LR3 can improve body composition by enhancing nutrient partitioning (more nutrients going to muscle versus fat), it's primarily an anabolic agent for muscle growth, not a fat burner [15]. For pure fat loss, compounds like HGH Fragment 176-191 or Tesamorelin might be more appropriate.
What happens if I experience hypoglycemia?
If you feel shaky, dizzy, sweaty, or confused, consume fast-acting sugar immediately—juice, glucose tablets, or regular soda work fast. Symptoms should improve within 10-15 minutes. If someone becomes unconscious, call emergency services immediately. Prevention is key: always eat with your injection.
Further reading
History & related research
History · since 1992
The Enhanced Growth Factor Revolution
A 25-Year Journey from Australian Innovation to Biotechnology Standard—How a Small Adelaide Team Engineered a Molecule That Powers Modern Medicine
Read the full history of IGF-1 LR3Ready for the protocol?
Every dosing tier, administration route, timing note, and dose-adjustment rule for IGF-1 LR3, on one page.