IGF-1 LR3 vs PEG-MGF
Verdict: IGF-1 LR3 is the systemic, whole-body growth signal; PEG-MGF is the local, injury-triggered repair signal. LR3 is dosed daily and raises IGF-1 activity everywhere for hours; PEG-MGF is dosed after training to activate satellite cells in the muscle that was just worked. They are more often sequenced than chosen between — MGF on training days, LR3 on rest days — but as a single choice, LR3 for general anabolism and MGF for a specific lagging or injured muscle.
Side by side
| IGF-1 LR3 | PEG-MGF | |
|---|---|---|
| Typical dose | 20 mcg–50 mcg | 200 mcg–400 mcg |
| Frequency | daily, often post-training | 2–3x weekly, often post-training |
| Administration | subcutaneous injection | subcutaneous injection |
| Common vials | 1 mg | 2 mg, 5 mg |
| Typical mix | 1 mg + 2 ml water | 2 mg + 2 ml water |
| Units for typical dose | 8 units (40 mcg) | 20 units (200 mcg) |
What each actually is
IGF-1 LR3 is IGF-1 with a 13-amino-acid extension and one substitution that stops it binding the IGF-binding proteins, giving it a ~20-hour half-life and roughly 3× potency. MGF is a splice variant of IGF-1 produced in muscle after mechanical load; PEGylation extends its native minutes-long half-life to days.
Dosing and timing
IGF-1 LR3: 20–50 mcg daily, subcutaneous, commonly post-workout or on waking, cycles of 4–6 weeks. PEG-MGF: 200–400 mcg, 2–3× weekly, injected after training — many protocols use bilateral injections near the trained muscle, although systemic injection appears to work given the PEG half-life.
The hypoglycemia and growth caveats
LR3 is insulin-like — it can drop blood sugar noticeably, especially fasted, and long cycles raise concerns about promoting growth of anything that wants to grow. PEG-MGF has fewer systemic effects but far less human data. Neither is approved and both are prohibited in sport.
Can you stack them?
The classic sequencing runs PEG-MGF on training days and IGF-1 LR3 on rest days, so the two are not competing for the same receptor at the same time. Both are commonly stacked with a GH secretagogue pair (CJC-1295 + ipamorelin).
More comparisons
Educational comparison based on commonly published research protocols — not medical advice or an endorsement of any compound.