Growth hormone
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.
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IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 is a modified version of IGF-1, the growth factor the body uses to tell cells to grow, repair, and multiply. The modification keeps binding proteins from capturing it 1, so it stays active in the bloodstream much longer than natural IGF-1. The evidence behind it comes from animal studies; it is a research compound, not an FDA-approved drug.
Think of IGF-1 (a growth signal your liver releases in response to growth hormone) 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 (an increase in cell numbers), and it's the holy grail of muscle building 2.
IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 (Long Arginine 3-IGF-1) is a modified version of human IGF-1 (insulin-like growth factor 1, a growth-signaling hormone), 83 amino acids long. Two changes matter. A 13-amino-acid extension is added at one end, and the amino acid at position 3 is swapped from Glu to Arg. These changes cut binding to IGFBPs (IGF binding proteins, carriers that hold IGF-1 in the blood and keep it inactive) by about 1000-fold. So much more of it circulates free and active 6. IGF-1 LR3 attaches to the Type 1 IGF receptor (IGF-1R) with somewhat lower affinity (about 3-fold) than normal IGF-1 17. That turns on two signal chains inside cells, PI3K/Akt and Ras/MAPK/ERK 2. The PI3K/Akt chain promotes protein building by activating mTOR (a cell growth switch) and blocks protein breakdown by shutting down FOXO transcription factors (proteins that turn on breakdown genes) 1112. The ERK chain drives cell multiplication 2. Most muscle-building drugs mainly make cells bigger (hypertrophy). IGF-1 also wakes satellite cells (muscle stem cells) and creates new muscle fibers (hyperplasia (an increase in cell numbers)) 213. At supraphysiological concentrations (levels above what the body normally makes), it acts like insulin, which explains the risk of hypoglycemia (low blood sugar): it moves GLUT4 (a sugar transporter) to the cell surface and increases sugar uptake into cells 78.
Evidence check
Animal studies only — extensive
It has been studied a lot, but in animals, not people. Results in mice or rats often don't carry over to humans.
Every numbered marker on this page links to one of the 18 sources at the bottom.
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
The most-asked question
The research-reported range is 20–100 mcg, once daily.
The ceiling: 100 mcg once daily (exceeding this significantly increases side effect risk without proportional benefits)
Reconstitution, in plain words
Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for IGF-1 LR3:
If you have a 1mg (1000mcg) vial and add 2mL of BAC water, you get a concentration of 500mcg/mL. So every 0.1mL (10 units on an insulin syringe) equals 50mcg of IGF-1 (a growth signal your liver releases in response to growth hormone) LR3.
For a 50mcg dose at 500mcg/mL: draw 0.1mL (10 units). For 100mcg: draw 0.2mL (20 units). Always double-check your math—this peptide is potent!
Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with IGF-1 LR3's recorded schedule.
Injection sites & technique
Subcutaneous (under the skin) injection (under the skin) is most common; intramuscular (into a muscle) injection into specific muscles is also used for localized effects
Timing
Post-workout is ideal for training days—your muscles are like sponges ready to absorb nutrients. 18 On rest days, morning with breakfast works well. Some users split doses between pre and post-workout.
Always have food available! IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 can cause significant blood sugar drops 79. Eat a meal with protein and carbs within 30 minutes of injection. Never inject fasted unless you're very experienced.
If stacking with growth hormone (HGH), inject IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 at least 2-3 hours apart to avoid competition for receptors. Can be combined with MGF for potentially synergistic muscle-building effects.
The honest list
These show up most often. They usually fade as your body adjusts.
This is the most important side effect to understand. IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 acts like insulin and drives glucose into cells, which can leave you feeling shaky, dizzy, or weak 78.
What to do 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.
Redness, slight swelling, or itching at the injection site is normal and usually fades within a day 18.
What to do Rotate injection sites regularly. Use proper sterile technique. A cool compress can help if irritation occurs.
Some puffiness or bloating, especially in hands and face, as IGF-1 (a growth signal your liver releases in response to growth hormone) causes cells to hold more water 16.
What to do Usually mild and temporary. Moderate sodium intake, stay well-hydrated, and it typically resolves as your body adjusts or when you cycle off.
Particularly common in the first week as your body adjusts to the peptide.
What to do Stay hydrated, don't skip meals, and the headaches usually subside after the first week. If persistent, consider reducing dose.
Worth knowing about, but most people never see these.
IGF-1 (a growth signal your liver releases in response to growth hormone) can cause tissue growth including in joints, which some people experience as achiness or stiffness 1516.
What to do Often dose-dependent—reducing dose typically helps. Ensure adequate hydration and consider joint support supplements.
Particularly in hands or feet, potentially related to water retention pressing on nerves (similar to carpal tunnel).
What to do Reduce dose if symptoms appear. Usually resolves when cycling off. If persistent, discontinue and consult a healthcare provider.
Rare, but if any of these happen, stop and contact a medical professional.
If blood sugar drops too low, you may experience confusion, difficulty speaking, or loss of consciousness. This is a medical emergency 9.
What to do If symptoms are severe, consume fast-acting sugar immediately (juice, glucose tablets). If someone loses consciousness, call emergency services. This is preventable with proper food timing.
Week by week
Is it right for you?
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.
Higher hypoglycemia (low blood sugar) risk. The blood sugar-lowering effects add up dangerously. Requires medical supervision and dose changes.
Extremely dangerous combination. Both dramatically lower blood sugar. Can cause severe, life-threatening hypoglycemia (very low blood sugar).
May increase bruising at injection sites. Not dangerous but worth monitoring.
Can hide hypoglycemia (low blood sugar) symptoms (shakiness, rapid heartbeat), making low blood sugar harder to notice. Use with caution.
May work well together for muscle growth. MGF works locally (near where it is injected) while IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 works through the whole body. Can be used together with careful timing.
Can be stacked for complementary effects: CJC increases natural GH release while IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 provides direct IGF effects. Space injections apart.
Safe to combine. GHRP-6 makes you hungry, which can actually help prevent hypoglycemia (low blood sugar) from IGF-1 (a growth signal your liver releases in response to growth hormone) LR3.
DANGEROUS combination. Both lower blood sugar dramatically. Severe hypoglycemia (very low blood sugar) risk. Do NOT combine unless under strict medical supervision.
Safe and potentially complementary. Both support muscle cell function and recovery.
Highly recommended! Adequate protein maximizes IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 benefits. Take protein with or shortly after injection.
May improve insulin sensitivity (how well your body responds to insulin), which could raise hypoglycemia (low blood sugar) risk. Monitor blood sugar more carefully.
Can increase glucose (sugar) uptake, adding to hypoglycemia (low blood sugar) risk. Use lower doses of both if combining.
If you're pushing hard in the gym and want to maximize every rep, IGF-1 (a growth signal your liver releases in response to growth hormone) 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.
Train hard, recover faster. IGF-1 (a growth signal your liver releases in response to growth hormone) 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.
Looking to build muscle while losing fat? IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 helps shuttle nutrients into muscle cells while improving how your body uses fat for fuel 815. Combined with proper diet, it supports that lean, muscular physique.
IGF-1 (a growth signal your liver releases in response to growth hormone) is your body's natural repair signal. The LR3 version stays active longer, potentially helping injured tissues heal more completely 15. Athletes recovering from muscle strains or tears may find it particularly beneficial.
IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 has been extensively studied in research settings and shows a predictable side effect profile when used responsibly. The primary concern is low blood sugar (hypoglycemia (low blood sugar)), which is manageable with proper nutrition timing 79. 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. 18 Always work with a healthcare provider familiar with peptide research when using any research compound.
Keeping it good
Keep your IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 powder refrigerated at 36-46°F (2-8°C) for storage up to 1 month. For longer storage, freeze at -4°F (-20°C) or below. The powder is quite stable when kept cold and away from light.
Once mixed with bacteriostatic water, refrigerate at 36-46°F (2-8°C). Never freeze the mixed solution—ice crystals will destroy the peptide structure. Keep away from light and use within 28-30 days.
Not our opinion — the published record
2001
This foundational study showed that LR3 IGF-I binds much less to IGF binding proteins (carrier proteins that hold IGF-1 in the blood) than regular IGF-1 does. That explains why it stays active in the bloodstream much longer and is more available to tissues.
Prelle K, Stojkovic M, et al.
2003
Researchers found that Long R3 IGF-I makes cells multiply (hyperplasia) through two signaling routes, ERK and PI3K. This explains IGF-1's unusual ability to create new cells, not just make existing cells bigger.
Sundgren NC, Giraud GD, et al.
2003
This study showed that LR3 IGF-I can get around IGF binding proteins, which normally hold IGF-1 back. That explains why LR3 is more active: it reaches target tissues more effectively than regular IGF-1.
Boes M, Dake BL, et al.
2019
LR3 IGF-I treatment effectively limited muscle loss in a cancer cachexia model (an animal model of cancer-related wasting), showing strong anti-catabolic effects (it blocks tissue breakdown) and an ability to protect muscle under conditions that normally cause severe wasting.
Levolger S, Wiemer EAC, et al.
2023
Purified LR3 IGF-1 worked well at making cells multiply, about as well as standard IGF-1. This confirms that the changes to the molecule keep its biological function while extending its active lifespan.
Lu Z, Liu N, et al.
1993
In direct comparisons, IGF-I bound IGF-binding proteins (IGFBP-3, IGFBP-4 and total rat plasma IGFBPs) with approximately 1000-fold higher affinity than LR3 IGF-I. The weaker binding made LR3 IGF-I 5-10 times more potent in cultured myoblasts (young muscle cells) and 6 times more potent for growth in rats. The same study found that LR3 IGF-I was cleared from rat plasma (blood) more quickly than IGF-I, precisely because it does not bind to binding proteins.
Ballard FJ, Walton PE, Bastian S, Tomas FM, Wallace JC, Francis GL
1997
In pigs and marmoset monkeys, IGF-I variants that bind poorly to IGF-binding proteins, including LR3 IGF-I, lowered blood glucose (sugar) 2- to 3-fold more strongly than regular IGF-I and kept it low for much longer, giving a roughly 4- to 8-fold bigger total blood-sugar-lowering effect (hypoglycaemic effect).
Tomas FM, Walton PE, Dunshea FR, Ballard FJ
1992
In muscle cells, IGF-I raised glucose uptake within about 10 minutes by moving glucose transporters (GLUT1 and GLUT4, which carry sugar into cells) to the cell surface, with no new protein building needed. Longer exposure also increased the amount of transporter the cells made.
Bilan PJ, Mitsumoto Y, Ramlal T, Klip A
2025
The FDA label for mecasermin (lab-made human IGF-1) reports hypoglycemia (low blood sugar) in 30 of 71 trial subjects (42%), including 5 severe episodes and 4 hypoglycemic seizures. It directs that each dose be given shortly before or after (plus or minus 20 minutes) a meal or snack, and not given if the meal is skipped.
Ipsen Biopharmaceuticals, Inc.
If this isn't the right fit
Your questions
Regular IGF-1 (a growth signal your liver releases in response to growth hormone) 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 13.
IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 works much like insulin: it drives nutrients (including sugar) into your cells 78. If you don't have enough sugar in your blood, your blood sugar drops too low (hypoglycemia (low blood sugar)). That brings shakiness, dizziness, confusion, or worse. Always eat a meal with protein and carbs within 30 minutes of your injection.
Yes, many users inject intramuscularly (into a muscle) into target muscles hoping for site-specific enhancement. However, IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 circulates systemically (affecting the whole body) regardless of injection site. Local injections may provide some preferential local effects, but the peptide will benefit your whole body, not just one muscle.
Most protocols run 4-6 weeks on, followed by at least 4 weeks off. 18 This allows IGF-1 (a growth signal your liver releases in response to growth hormone) receptors to resensitize. Running too long without breaks can lead to receptor downregulation (dials down activity), diminishing returns, and increased side effect risk. Some users do 5 days on, 2 days off throughout their cycle.
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.
IGF-1 (a growth signal your liver releases in response to growth hormone) is a growth factor that can stimulate cell division, which is concerning for anyone with existing cancer or pre-cancerous conditions 25. 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.
While IGF-1 (a growth signal your liver releases in response to growth hormone) LR3 can improve body composition by enhancing nutrient partitioning (more nutrients going to muscle versus fat), it's primarily an anabolic (muscle-building) 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.
If you feel shaky, dizzy, sweaty, or confused, consume fast-acting sugar immediately—juice, glucose tablets, or regular soda work fast. 9 Symptoms should improve within 10-15 minutes. If someone becomes unconscious, call emergency services immediately. 9 Prevention is key: always eat with your injection.
18 sources
Every numbered marker on this page points to one of these. Same sources, same numbering as the IGF-1 LR3 research profile on Peptide Initiative.
Want the deep science?
Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.
Open the research profileThis guide is education, not medical advice. IGF-1 LR3 is a research compound that is not FDA-approved for human use. Talk to a clinician before taking anything.
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