PinnyPeptide

B7-33 vs IGF-1 LR3

Side-by-side comparison: effects, dosing ranges, side effects, regulatory status, and reconstitution.

Peptide A

B7-33

Muscle Growth

Single-chain relaxin peptide analog with anti-fibrotic and cardioprotective activity.

Peptide B

IGF-1 LR3

Muscle Growth

Long-acting IGF-1 analog with reduced binding-protein affinity for sustained signaling.

Typical vial

2 mg

Typical dose

1000-2000 mcg

Half-life

~2-3 hours

FDA status

Not FDA approved.

Typical vial

1 mg

Typical dose

20-50 mcg

Half-life

~20-30 hours

FDA status

Not FDA approved. Native recombinant rhIGF-1 (mecasermin/Inc…

B7-33 effects

  • Anti-fibrotic action in heart, lung, kidney tissue
  • Activates RXFP1 receptor via cGMP signaling arm
  • Vasodilatory effects
  • May support tissue remodeling and scar prevention
  • Reduces collagen deposition in injury models

IGF-1 LR3 effects

  • Sustained IGF-1 receptor activation (20-30 hour half-life)
  • Muscle cell hyperplasia (increased cell number, not just size)
  • Anabolic signaling via PI3K-Akt-mTOR pathway
  • Improved nutrient partitioning toward muscle
  • Enhanced recovery from training-induced damage

B7-33 side effects

  • Human safety data essentially absent
  • Theoretical: hypotension from vasodilation
  • Injection-site reactions
  • Possible effect on uterine / cervical tissue (relaxin family)

IGF-1 LR3 side effects

  • Hypoglycemia (real risk — IGF-1 has insulin-like activity)
  • Joint pain and stiffness
  • Carpal tunnel-like symptoms
  • Lethargy / lightheadedness from glucose drops
  • Possible tumor-promoting effects (theoretical, dose-dependent)
  • Localized lipohypertrophy or muscle asymmetry with site injection

B7-33 dosing ranges

Research / anti-fibrotic

1-2 mg · Daily (SubQ or IV in preclinical work) · Per research protocol

IGF-1 LR3 dosing ranges

Research / muscle hypertrophy

20-50 mcg · Once daily (SubQ or IM), pre- or post-workout · 30-50 days per cycle

Site-specific injection (research)

20-40 mcg per site · Into trained muscle, post-workout · 30-50 days per cycle

Full B7-33 guide → Full IGF-1 LR3 guide →

B7-33 vs IGF-1 LR3 — common questions

What is the difference between B7-33 and IGF-1 LR3?

B7-33: Single-chain relaxin peptide analog with anti-fibrotic and cardioprotective activity. Typical dose 1000-2000 mcg. IGF-1 LR3: Long-acting IGF-1 analog with reduced binding-protein affinity for sustained signaling. Typical dose 20-50 mcg. Both fall under the Muscle Growth category.

Can you stack B7-33 and IGF-1 LR3?

Stacking B7-33 with IGF-1 LR3 is a protocol-design question best raised with a clinician — it depends on your goal, current bloodwork, and whether both peptides target overlapping mechanisms. Both peptides should be tracked independently with separate injection sites and timing. PinnyPeptide supports multi-peptide stacks with automatic injection site rotation.

Which is dosed more frequently, B7-33 or IGF-1 LR3?

B7-33 is typically dosed: Daily (SubQ or IV in preclinical work) for Research / anti-fibrotic. IGF-1 LR3 is typically dosed: Once daily (SubQ or IM), pre- or post-workout for Research / muscle hypertrophy; Into trained muscle, post-workout for Site-specific injection (research).

Are B7-33 and IGF-1 LR3 FDA approved?

B7-33: Not FDA approved. IGF-1 LR3: Not FDA approved. Native recombinant rhIGF-1 (mecasermin/Increlex) is FDA approved for severe primary IGF-1 deficiency in children, but IGF-1 LR3 itself is not.

Related peptide comparisons

ace-031 vs b7-33ara-290 vs b7-33b7-33 vs bpc-157b7-33 vs follistatinb7-33 vs gdf-8-95ace-031 vs igf-1-lr3

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