HGH and IGF-1 LR3
Does adding IGF-1 LR3 to growth hormone build more muscle, and why do experienced users warn against it?
Reviewed by the amino101 editorial team. .
Also searched as growth hormone and IGF-1 stack, HGH LR3 stack, GH and IGF-1 LR3 cycle, bodybuilding peptide stack.
HGH is recombinant human growth hormone, a 191 amino acid protein identical to what the pituitary makes. It is an approved drug for growth hormone deficiency and is used off-label for fat loss, muscle preservation, recovery, and anti-aging.
IGF-1 LR3 is a modified, long-acting version of insulin-like growth factor 1 that resists binding proteins and stays active for most of a day. People use it for muscle growth and recovery, and it carries a real risk of low blood sugar.
HGH and IGF-1 LR3 are stacked in bodybuilding circles on a simple theory: growth hormone makes the liver produce IGF-1, which does most of the anabolic work, so adding IGF-1 directly should do more. The two sit one step apart on the same axis and could hardly differ more in what is known about them. HGH is recombinant somatropin, an approved drug since 1985 with decades of human data, including trials in healthy adults showing a few kilograms of lean mass gained and fat lost, no improvement in strength, and a meaningful rate of edema, joint pain and carpal tunnel. IGF-1 LR3 is a modified IGF-1 built as a cell culture reagent, with a 20 to 30 hour half-life because it escapes the binding proteins, no human trial of any kind, and a real risk of hypoglycemia because it acts like a weak, long lasting insulin. Both are prohibited by WADA. HGH is a controlled prescription drug in most countries and federal law restricts its off label distribution in the US. Everything the stack is used for rests on mechanism and anecdote.
This page covers the protocol that circulates, the reason the two are injected at different times of day, the blood sugar problem that runs in opposite directions, and why the honest advice for most people is to not do this. For the head to head see IGF-1 LR3 vs HGH, and for the context that matters most, that no peptide builds muscle like an anabolic steroid, see peptides vs steroids. Everything here is educational background, not a plan.
Why people combine HGH and IGF-1 LR3
Somatropin binds growth hormone receptors on the liver and drives IGF-1 production, and that IGF-1 activates the PI3K-Akt-mTOR pathway in muscle to raise protein synthesis. It also has direct effects of its own: lipolysis in fat cells, raised blood glucose, collagen turnover. LR3 skips the liver and delivers IGF-1 receptor signaling directly, unbound and for most of a day. The theory is that growth hormone covers fat loss and the systemic effects while LR3 covers the anabolic signal. No human study has tested whether the sum is larger than either part.
Growth hormone opposes insulin and raises glucose for hours after a dose; the trials in healthy adults show reduced insulin sensitivity in a dose dependent way. LR3 lowers glucose by activating the insulin receptor at the concentrations an unbound, long acting analog reaches. People stack them partly because they hope the effects cancel, and inject them at different times of day so the glucose swings do not land together. In practice the result is a day that swings both ways, which is why bloodwork and a glucose meter are not optional with this pair.
In healthy adults, growth hormone adds a few kilograms of lean mass over months, and a good part of that is water and connective tissue rather than contractile muscle; strength does not improve in controlled studies. LR3 has rodent data showing more protein synthesis and nitrogen retention than native IGF-1 and nothing in people. The stack's reputation comes from its use alongside anabolic steroids, where growth hormone's effects on muscle are amplified. On its own, it is a modest tool with an outsized side effect list.
Two reasons come up consistently. First, nothing about LR3 can be undone once injected; a 20 to 30 hour half-life means a mistake with the dose or a skipped meal plays out over a day. Second, both compounds push IGF-1 signaling, which drives cell growth without discrimination, and running them together doubles the theoretical cancer concern while adding a hypoglycemia risk that has caused serious episodes in community reports, especially when insulin is also in the picture. Secretagogues give a milder version of the same idea with far less risk.
HGH and IGF-1 LR3 dosage and protocol
What appears in research and community protocols for each compound in the stack. Not a prescription.
| Peptide | Dosage | Frequency | Timing and route |
|---|---|---|---|
| HGH (Somatropin) | 2 to 4 IU | once daily, or split into morning and evening doses | subcutaneous, belly or thigh, on waking before food or after training; never at the same time as the LR3 dose |
| IGF-1 LR3 | 20 to 50 mcg | once daily on training days, starting at 20 mcg | subcutaneous after training, with a meal containing carbohydrate; never fasted and never before bed |
The two halves run on different lengths. HGH is run for 3 to 6 months minimum for body composition, because the fat loss and lean mass changes take that long. LR3 is run in short blocks of 4 to 6 weeks, then at least 4 weeks off, on the theory that IGF-1 receptors downregulate and because nobody has long term safety data on sustained unbound IGF-1. So the common pattern is an LR3 block inside a longer growth hormone run, repeated at most a couple of times, with IGF-1 and fasting glucose checked before each block.
- •Neither dosage changes because of the stack, but the LR3 end is kept low. Most people find little above 50 mcg except side effects, and 20 mcg is the reported starting point.
- •The 2 to 4 IU growth hormone range is body composition territory; 1 to 2 IU is what people run for recovery and skin. Tingling hands and water retention scale with dose.
- •Separate the injections by hours, not minutes. Growth hormone on waking and LR3 after an afternoon or evening session with food is the usual split.
- •Keep fast carbohydrate on hand for the first several LR3 doses until the glucose response is known. Shakiness, sweating and brain fog an hour or two after a dose mean the meal was not enough.
- •Growth hormone should come from a pharmacy. Counterfeit and underdosed somatropin is rampant on the grey market, and LR3 is fragile enough that degraded product is common, so third party testing matters more than the brand.
Work out syringe units for any of these in the dosage calculator.
Can you mix HGH and IGF-1 LR3 in one syringe?
These are never mixed, and the reason is pharmacology rather than chemistry. Growth hormone raises blood glucose for several hours after a dose and LR3 lowers it for most of a day, so the two are injected at different times, growth hormone on waking or before bed and LR3 after training with food, specifically so the glucose effects do not overlap. Both reconstitute in bacteriostatic water and keep in the fridge for 2 to 4 weeks; LR3 is handled gently and never shaken because the protein is fragile. Somatropin is measured in IU, at the current standard of 3 IU per mg, and LR3 in micrograms from a 1 mg vial in 2 mL, so the syringe math is different for each; the calculator handles both. People who split growth hormone into morning and evening doses keep the evening dose well away from the LR3 injection.
What to expect, week by week
- Week 1 to 2
Water retention, puffy hands and feet and deeper sleep from growth hormone, with tingling fingers above 2 IU. From LR3, possible shakiness, sweating or brain fog an hour or two after a dose if food was skipped, and better pumps in training.
- Week 2 to 4
Fluid effects plateau. Muscle fullness and vascularity from LR3, faster recovery between sessions, mild headaches in some. Fasting glucose may tick up from growth hormone even while LR3 pulls it down after doses.
- Week 4 to 6
The end of the LR3 block. Modest strength and size progress if training and food are in place; diminishing returns and rising side effects if the dose keeps climbing. IGF-1 is elevated on bloodwork from both sources.
- Month 2 to 6
Growth hormone continues alone. Gradual fat loss around the midsection, muscles look fuller from water and glycogen, and a few pounds of lean mass in most responders over 3 to 6 months. Strength gains are not expected from the hormone itself.
Side effects and cautions
- ▲Hypoglycemia from LR3: shakiness, sweating, hunger and brain fog an hour or two after a dose
- ▲Elevated fasting glucose and reduced insulin sensitivity from growth hormone
- ▲Fluid retention, swollen hands and feet, joint pain and stiffness
- ▲Carpal tunnel symptoms, tingling and numb fingers
- ▲Headache and lethargy after dosing
- ▲Injection site pain or bruising, and fat loss at the site with repeated growth hormone injections
- ■Any history of cancer. Both compounds drive IGF-1 signaling, which promotes cell growth without discrimination, and LR3 keeps the signal on for most of a day. This is the clearest reason to skip the stack.
- ■Insulin use, diabetes medication, fasting or very low carbohydrate diets. LR3 plus insulin has caused serious hypoglycemia in community reports, and low glycogen makes a drop harder to reverse.
- ■Prediabetes or raised fasting glucose. Growth hormone can push it over the line, and the LR3 dips do not fix the underlying insulin resistance.
- ■Tested athletes. Both are prohibited by WADA, and growth hormone is detectable.
- ■Anyone sourcing growth hormone outside a pharmacy. Counterfeit somatropin is the norm on the grey market, and HGH is a controlled prescription drug with legal exposure that research peptides do not carry.
This is a stack for a narrow group: experienced users whose goal is muscle specifically, who have a pharmacy source for growth hormone, who will run bloodwork for IGF-1 and glucose, who will dose LR3 low with food and keep sugar on hand, and who have no cancer history and no drug testing in their future. For that group the logic is coherent and the evidence is thin. For everyone else the answer is not to do this. Growth hormone alone at 1 to 2 IU is the better understood tool for recovery and body composition, secretagogues are better understood still, and neither carries the hypoglycemia risk or the doubled IGF-1 exposure that LR3 adds. No peptide stack builds muscle like a steroid, and this one is sold on the reputation it earned next to steroids. This page is educational and not medical advice; anyone with prediabetes, a cancer history, or insulin in the picture has a hard reason to leave it alone.
HGH and IGF-1 LR3: frequently asked
Can you take HGH and IGF-1 LR3 together?
People do, injected at different times of day so the glucose effects do not overlap: growth hormone on waking or before bed, LR3 after training with a carbohydrate meal. There is no human study of the combination. Growth hormone already raises IGF-1 through the liver, so the stack layers direct IGF-1 receptor signaling on top of that, which is the point for the people who run it and the problem for everyone concerned about cell growth.
What is the HGH and IGF-1 LR3 dosage?
Reported protocols use growth hormone at 2 to 4 IU daily, often split morning and evening, and LR3 at 20 to 50 mcg once daily after training, starting at 20 mcg. These are the same ranges as each compound alone; the stack does not raise either. The LR3 block is kept to 4 to 6 weeks inside a longer growth hormone run. Both are listed on the peptide dosage chart.
Does IGF-1 LR3 cause low blood sugar?
Yes, reliably, which is why it is dosed with food. IGF-1 is structurally close enough to insulin to activate the insulin receptor, and LR3 is unbound and active for 20 to 30 hours, so the drop can last for hours and cannot be reversed once the dose is in. Shakiness, sweating, hunger and brain fog are the signs. Eating carbohydrate around the dose, starting at 20 mcg and keeping glucose tablets nearby for the first several doses are the community rules; stacking it with insulin is where the serious episodes come from.
Does the HGH and IGF-1 LR3 stack build muscle like steroids?
No, and the gap is large. Growth hormone in healthy adults adds a few kilograms of lean mass over months, much of it water and connective tissue, with no strength improvement in controlled trials. LR3 has no human data at all. Anabolic steroids act directly on the androgen receptor in muscle and produce gains in weeks that this stack does not approach. The reputation of the pair comes from its use alongside steroids, not instead of them; see peptides vs steroids.
Is HGH and IGF-1 LR3 banned?
Both are prohibited by WADA, growth hormone under S2 and LR3 as a growth factor. Growth hormone is also a controlled prescription drug in most countries; in the US, distribution for off label use is restricted by federal law, which puts it in a different legal category from research peptides. LR3 is sold as a laboratory reagent. For detection, see do peptides show up on a drug test.
Is a secretagogue stack a safer alternative?
Yes. CJC-1295 no DAC with ipamorelin raises your own growth hormone in pulses, keeps the pituitary feedback loop intact so IGF-1 rises modestly, carries no hypoglycemia risk and has a far milder side effect profile. It is weaker than growth hormone and much weaker than this stack is hoped to be, but for recovery, sleep and gradual body composition change it is the better understood tool. The protocol is at the CJC-1295 and ipamorelin stack.
Related reading
Pulsatile growth hormone release
Visceral fat loss with growth hormone support
The messenger and the hormone. Why one is a cell culture reagent and the other is an approved drug.
Inject the hormone itself, or ask your pituitary to make more? The trade-offs are not subtle.
Two IGF-1 family compounds sold for muscle. Neither has a human trial. What is the difference, and does the classic alternating protocol make sense?
Guide
Guide
Buying
Safety
Sources
- Effects of human growth hormone in men over 60 years old. New England Journal of Medicine, 1990
- Systematic review: the safety and efficacy of growth hormone in the healthy elderly. Annals of Internal Medicine, 2007
- Long R3 IGF-1: a potent IGF-1 analog with reduced binding protein affinity. Journal of Molecular Endocrinology, 1992
- Effects of IGF-1 and LR3 IGF-1 on protein metabolism and growth in rats. Journal of Endocrinology, 1995