Half-lifeUnknown in people. Community sources often claim 20–30 hours, but rat studies found it leaves the blood faster than normal IGF-1; its extra punch comes from escaping binding proteins, not from lasting longer.
Vial sizes0.1 mg, 1 mg
The simple version
What it does
It acts like a stronger version of IGF-1, the hormone that helps muscle and other tissue grow.
How people take it
People report 20–50 µg once a day, often on training days, with a meal that has carbs.
Know this
It can drop your blood sugar dangerously, and it has never been tested in people.
What it is
IGF-1 is a hormone your liver makes when growth hormone tells it to; it helps muscle, bone and other tissue grow, and it acts a bit like insulin. IGF-1 LR3 is a changed version made in Australia in the early 1990s for lab work, built so the body's 'holding' proteins can't grab it, which leaves more of it free and active. It has never been tested in people, and it's not the same as the one approved IGF-1 drug (mecasermin), which treats rare growth disorders in kids.
How it works
Normally, holding proteins in your blood grab almost all IGF-1 and keep it in check. LR3 slips past them, so a small dose hits much harder than the same amount of normal IGF-1, acting straight on muscle and other tissue. It also works like insulin, so it can drop your blood sugar.
What people use it for
Muscle growth and recovery (bodybuilding)
Losing fat while keeping or building muscle
Lab cell-growing work (what it was made for)
The evidence
Mostly animal studies
Almost all the data comes from rats and cells. In rats it was 1.5 to 2 times stronger than normal IGF-1 for weight gain and organ growth, but barely better at protecting muscle during steroid-caused wasting or food cuts. There are no human trials at all, so dose, safety and benefits in people are unknown; the approved IGF-1 drug shows the main danger in people is low blood sugar.
After a workout, with or right before a meal that has carbohydrates. Never on an empty stomach.
Cycle
4–6 weeks on, then at least as long off
Route
Subcutaneous injection (some inject into the trained muscle)
Why: It acts like insulin and can drop your blood sugar, so people take it with food. Cycles are kept short because the body seems to stop responding as well with nonstop use, and because long-term safety is unknown.
Low/starter
Reported
Dose
10–20 µg
How often
Once a day
When
With a carb-containing meal; have fast sugar on hand
Cycle
First 1–2 weeks of a cycle
Route
Subcutaneous injection
Why: There's no human dosing data, so starting very low is the only way to see how hard it hits your blood sugar.
Start at the low end, and change one thing at a time. If you take medication or have a health condition, check with a doctor first.
We may earn a commission from these links. Counts include one syringe and two swabs per dose.
Stay safe
Side effects
Low blood sugar: shaky, sweaty, fast heartbeat, confused; bad cases can cause seizures or passing out
Redness or lumps where you inject
Headache
Jaw pain or a full, puffy feeling in the face
Water retention (puffiness)
Joint pain
Organs or tissue growing too much with long-term high use (seen with IGF-1 drugs)
Skip it if
Cancer now or in the past (IGF-1 helps cells grow and survive, and high IGF-1 is linked to some cancers)
Diabetes, or taking insulin or diabetes pills (high risk of dangerously low blood sugar)
Past episodes of low blood sugar
Pregnant or breastfeeding
Under 18 (can affect growing bones)
Diabetes-related eye damage (retinopathy)
Anyone who will be alone or driving soon after a dose
Interactions
Insulin, sulfonylureas and other diabetes drugs: together they can cause severe low blood sugar
Alcohol makes low blood sugar more likely
Growth hormone, growth hormone peptides and steroids: stacking adds up the growth effects and the side-effect risk
Get help right away for swelling of the face or throat, trouble breathing, chest pain, or a spreading, hot, red injection site.
Storage & legal
Storage
Powder: fridge or freezer. Mix with weak acetic acid (0.6%) or bacteriostatic water as directed; once mixed, keep it in the fridge and use within about 3–4 weeks. At tiny amounts it sticks to plastic and glass, so don't dilute it more than you need to.
Legal status
FDA: Not approved for any use and never tested in human trials. Sold only as a research chemical. The only approved IGF-1 drug is mecasermin (Increlex), a different product.
Sport (WADA): Prohibited at all times (S2, growth factors: IGF-1 and its analogues).
Common questions
What does low blood sugar feel like, and what should I do?
You feel shaky, sweaty and hungry, with a racing heart and foggy thinking. Eat or drink fast sugar right away (juice, regular soda, glucose tabs), then have a real meal. If someone is confused or passes out, call emergency services; this is why it's taken with food and never before driving.
Is it the same as the approved IGF-1 drug?
No. The approved drug, mecasermin, is regular IGF-1 for kids with a rare growth disorder, and its label warns about low blood sugar and says to dose within 20 minutes of a meal. IGF-1 LR3 is a different, harder-hitting molecule that has never been safety-tested in people.
Can I take it with growth hormone peptides?
People do, but there's no safety data on the combo. Stacking pushes IGF-1 activity even higher, which adds to both the low-blood-sugar risk and the long-term cancer worry.
Sources
Francis GL, et al. Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency. J Mol Endocrinol. 1992;8(3):213-23. PubMed 1378742
Tomas FM, et al. Superior potency of infused IGF-I analogues which bind poorly to IGF-binding proteins is maintained when administered by injection. J Endocrinol. 1996;150(1):77-84. PubMed 8708565
Tomas FM, et al. Insulin-like growth factor-I (IGF-I) analogue, LR(3)IGF-I, ameliorates the loss of body weight but not of skeletal muscle during food restriction. Growth Horm IGF Res. 2001;11(2):92-103. PubMed 11472075
INCRELEX (mecasermin) injection. FDA prescribing information. Source
Dominikowski A, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. PubMed 42395176