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The Peptide Effect
preclinicalGrowth Hormone

Ipamorelin

Also known as: IPA, Ipamorelin Acetate, NNC 26-0161

Ipamorelin is a highly selective growth hormone secretagogue peptide (GHRP) that stimulates GH release through the ghrelin/GHS receptor. It is distinguished from other GHRPs by its remarkable selectivity — it triggers robust GH release with minimal impact on cortisol, prolactin, or appetite. This clean side-effect profile has made it one of the most popular peptides in anti-aging and performance optimization protocols.

Key Facts

Mechanism
Ipamorelin is a pentapeptide ghrelin mimetic that selectively activates the growth hormone secretagogue receptor (GHS-R1a) on pituitary somatotroph cells, initiating a GH release pulse. Unlike GHRP-6 and GHRP-2, ipamorelin does not significantly activate the ACTH-cortisol axis or stimulate prolactin release, even at high doses. It also lacks the potent appetite-stimulating (orexigenic) effects of other ghrelin receptor agonists. This selectivity is attributed to its specific receptor binding profile that preferentially triggers the GH pathway without broad hypothalamic activation.
Research Status
preclinical
Half-Life
~2 hours
Molecular Formula
C₃₈H₄₉N₉O₅
Primary Use
Growth Hormone

Benefits

  • Clean, selective GH release without cortisol or prolactin spikesstrong
  • Improved sleep quality and increased slow-wave sleep durationmoderate
  • Supports fat loss through enhanced lipolysis and GH-mediated metabolismmoderate
  • Promotes lean muscle mass gains and nitrogen retentionmoderate
  • Anti-aging effects including improved skin quality, energy, and vitalitypreliminary
  • Does not significantly increase hunger, unlike GHRP-6 and other ghrelin mimeticsstrong

Dosage Protocols

RouteDosage RangeFrequencyNotes
Subcutaneous injection100–300 mcg2–3× dailyStandard protocol; inject 30 minutes before meals or at bedtime on an empty stomach
Subcutaneous injection100 mcg ipamorelin + 100 mcg CJC-12952–3× dailyMost popular combination stack for synergistic GH release. Pre-bed dose is considered the most important.
Subcutaneous injection200 mcgOnce daily at bedtimeSimplified once-daily protocol targeting the nocturnal GH pulse; suitable for beginners

Medical disclaimer

Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.

Side Effects

  • Mild headache, especially in the first few days of usecommon
  • Lightheadedness or dizziness shortly after injectionrare
  • Transient water retentionrare
  • Injection site irritation (redness, minor swelling)common
  • Mild nausea, typically dose-dependent and transientrare

Frequently Asked Questions

When is the best time to inject ipamorelin?
The most important dose is at bedtime, approximately 30 minutes before sleep, to amplify the natural nocturnal GH surge. Additional doses can be taken upon waking (before breakfast) or 30 minutes before a workout. Always inject on an empty stomach — elevated blood sugar and insulin significantly blunt GH release. Avoid eating for at least 30 minutes after injection.
Why is the CJC-1295 + ipamorelin combo so popular?
CJC-1295 (a GHRH analog) amplifies the GH pulse, while ipamorelin (a GHRP) initiates the pulse. They act on different receptors (GHRH-R and GHS-R) and produce a synergistic effect — the combined GH release is significantly greater than either alone. Ipamorelin is the preferred GHRP for this stack because it does not elevate cortisol, prolactin, or appetite like GHRP-6 or GHRP-2 would.
How does ipamorelin compare to GHRP-6?
Ipamorelin is far more selective than GHRP-6. GHRP-6 produces a strong GH release but also significantly increases appetite (via direct ghrelin activation), raises cortisol and prolactin, and can cause water retention. Ipamorelin produces a comparable GH release without these side effects. GHRP-6 may be preferred by those specifically seeking appetite stimulation for bulking, but ipamorelin is considered the cleaner choice for most users.
Does ipamorelin cause hunger?
Unlike GHRP-6 and GHRP-2, ipamorelin does not significantly stimulate appetite. While it does act on the ghrelin receptor, its binding profile is selective enough that it does not trigger the broad orexigenic (appetite-stimulating) response seen with less selective GHRPs. Some users report mild hunger, but it is not a prominent side effect.
Do I need to cycle ipamorelin?
There is no definitive clinical guidance on cycling ipamorelin. Common approaches include 8–12 weeks on followed by a 4-week break, or continuous use with periodic IGF-1 blood work monitoring. Some practitioners prescribe it continuously for anti-aging purposes. The pulsatile nature of ipamorelin-induced GH release may reduce the risk of receptor desensitization compared to sustained GH elevation. Consult a healthcare provider for personalized guidance.

References

  1. 1
    Ipamorelin, the first selective growth hormone secretagogue(1998)PubMed ↗
  2. 2
    The selective growth hormone secretagogue ipamorelin does not affect cortisol, prolactin and other anterior pituitary hormones in healthy volunteers(1999)PubMed ↗
  3. 3
    Growth hormone secretagogues: history, mechanism of action, and clinical development(2005)PubMed ↗
  4. 4
    Comparison of the pharmacological properties of GH secretagogues: GHRP-6, GHRP-2, hexarelin, and ipamorelin(2001)PubMed ↗

Last updated: 2026-02-14