Peptides
IGF-1 LR3
Also called Long R3 IGF-1 · LR3
IGF-1 LR3 is used experimentally for muscle fullness, growth and recovery. It is a modified growth factor, not a proven muscle-building medicine; the practical concerns are uncertain lasting gains, glucose effects and a product whose real contents may differ from its label.
Dosage & duration
One self-reported example; not a common or recommended cycle.
One reported use
Reported use · unapproved regimen- Dose
- 40 mcg total daily
- How often
- Described as 20 mcg before and 20 mcg after training; route not verified
- How long
- 25 days
The report does not establish safety, product authenticity or an optimal training window.
Do not import a mecasermin prescription dose into an LR3 protocol.
Judging an LR3 result
Fullness, lasting growth and glucose are separate
What people seek
-
Size and recovery
Users hope for fuller muscles, lasting growth and better recovery.
What needs attention
-
Glucose effects
IGF variants lowered blood glucose in animal studies; human risk is not quantified here.
A fuller look A short-term change in appearance does not establish new muscle tissue.
Why people add it to a training plan
Bodybuilding discussions focus on size, pumps and recovery, often with other hormones. Those stories cannot separate temporary fullness from added muscle or isolate LR3’s contribution when several drugs change together.
LR3 versus DES and prescription IGF-1
LR3 and DES are different modified research molecules. Neither is interchangeable with prescription mecasermin. A medical dose for another IGF-1 product does not validate a bodybuilding dose for LR3.
Long name does not prove a long human half-life
The modification changes binding to carrier proteins. In cited animal work LR3 actually left plasma faster than native IGF-I. Biological effects and time in blood are different, so the plot does not establish an all-day anabolic window.
Glucose is a real concern
IGF variants lowered glucose in animal experiments. That does not give a reliable human risk percentage, and a meal-timing trick is not proof of safety. Symptoms such as confusion, faintness or marked weakness need attention, not an extra workout.
Model details: IGF-1 LR3 · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
Retained only as an explicit mathematical timing assumption; not a verified human half-life. No concentration-unit amplitude is supported.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 12 hours
- Absorption half-life assumed
- 3 hours
- Reference amount for the relative scale
- 1 mg
- Absorption half-life is assumed to be one quarter of the slower timescale (3 h); it is not a measured absorption parameter.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Potency or duration of biological response is not an elimination half-life. No human product/route Cmax was verified.
- Tomas et al.: IGF-I analogues in rats
Rat study explicitly distinguishes faster LR3 clearance from greater biological effects.
- IGFBP interactions, clearance and IGF analogue activity
Original animal experiments associate low binding-protein affinity with faster removal from plasma.
igf-1-lr3-relative-timing-2026-10 · version 1
Common questions
Is LR3 a prescription IGF-1 substitute?
No. It is not interchangeable with mecasermin.
Does LR3 stay in the blood longer because it is called “Long”?
The name alone does not prove that. The cited animal comparison found faster plasma clearance than native IGF-I.
Sources Labels, studies and notes behind this guide
Catalog evidence: Animal or laboratory research. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- Main interest
- Reported goals; lasting gains are not established by anecdotes.
- Dose units
- Do not confuse mcg with mg or syringe marks.
- Key trade-off
- The evidence cannot define a safe bodybuilding threshold.
- 1. LR3 and IGF clearance experiments
Animal experiments found faster plasma removal of LR3 than native IGF-I despite greater biological potency.
- 2. IGF variants and glucose in pigs and marmosets
Primary animal study supports glucose-lowering concern, not a human incidence or safe-dose estimate.
- 3. Tomas et al.: IGF-I analogues in rats
Rat study explicitly distinguishes faster LR3 clearance from greater biological effects.
- 4. IGFBP interactions, clearance and IGF analogue activity
Original animal experiments associate low binding-protein affinity with faster removal from plasma.
- 5. Long IGF-I analogue structure and cell effects
Original analogue study: N-terminal extension and Arg3 substitution, reduced binding-protein interaction, context-dependent potency.
- 6. Tomas et al.: injected LR3IGF-I in rats
Original study explicitly reports faster circulation clearance despite stronger effects on selected endpoints; no human 20–30-hour PK evidence.
Related compounds and examples
Related compounds
MGF (Mechano Growth Factor)
MGF for muscle recovery and growth: reported dose claims, workout timing and the difference from PEG-MGF.
PEG-MGF (Pegylated MGF)
PEG-MGF versus MGF: muscle-growth claims, reported schedules and the limits of the longer-lasting promise.
IGF-1 DES
IGF-1 DES: workout and local-growth claims, reported amounts and how it differs from LR3.