Side-by-side · Research reference

IpamorelinvsRetatrutide

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

APhase 1Reviewed21/57 cited

BPhase 2Reviewed10/41 cited

Ipamorelin

Selective GHRP · Ghrelin Mimetic

200–300 mcgPer doseRaun 1998

Phase 1Evidence levelRaun 1998 Sigalos 2018

~2 hrHalf-lifeRaun 1998

SQ · Multiple sites · 1–3×/day

Retatrutide

Triple-receptor agonist · Phase 3

1–12 mgWeekly doseJastreboff 2023

24.2%Body-weight ↓Jastreboff 2023

~6 daysHalf-life (est)

SQ · Abdomen · Once weekly

01Mechanism of Action

Parameter

Ipamorelin

Retatrutide

Primary target

Ghrelin receptor (GHS-R1a) on anterior pituitaryRaun 1998

GLP-1R + GIPR + Glucagon receptor (triple agonism)Jastreboff 2023

Pathway

GHS-R1a binding → Gαq/11 → ↑intracellular Ca²⁺ → GH vesicle exocytosisRaun 1998 Bowers 1991

Triple-receptor activation → ↑insulin (GLP-1+GIP), ↓gastric emptying, ↑lipid handling, ↑energy expenditure (glucagon component)Jastreboff 2023

Downstream effect

GH pulse amplification, IGF-1 elevation, recovery and lipolytic effectsBowers 2002

Maximal weight loss across class. Glucagon component drives lipolysis and energy expenditure beyond GLP-1+GIP aloneJastreboff 2023

Feedback intact?

Yes — pulsatile pattern preserved; somatostatin feedback activeBowers 2002

—

Origin

Pentapeptide H-Aib-His-D-2-Nal-D-Phe-Lys-NH₂; rationally designed for ghrelin-receptor selectivityRaun 1998

Synthetic peptide engineered for balanced affinity at three incretin / glucagon receptorsJastreboff 2023

Antibody development

Not reported in short-term studies

—

02Dosage Protocols

Parameter

Ipamorelin

Retatrutide

Standard dose

200–300 mcg per injectionRaun 1998

Anecdotal community range; clinical doses 1–3 mg IV in trials.

12 mg / week (max efficacy)Jastreboff 2023

Phase 2 trial dose. Phase 3 dosing TBD.

Frequency

1–3× per day

Once daily pre-sleep is most common; twice or thrice for advanced users.

Once weekly

Lower / starter dose

100 mcg per dose

—

Evidence basis

Phase 1 + clinical practiceRaun 1998 Sigalos 2018

Phase 2 trial; Phase 3 ongoingJastreboff 2023

Duration

8–12 weeks on / 4 weeks off (anecdotal)

GHS-R desensitisation reported with continuous dosing.

Indefinite for chronic indication (presumed)

Reconstitution

Bacteriostatic water; typical 2 mL per 5 mg vial

Investigational; not commercially available

Timing

Pre-sleep + fasted preferred; 30 min away from food

Any time of day

Half-life

~2 hoursRaun 1998

Longer than GHRP-6 (15 min); shorter than CJC-1295-DAC (~8 days).

~6 days (estimated from class)

Titration schedule

—

2 mg → 4 mg → 8 mg → 12 mg over 16 weeks

04Side Effects & Safety

Parameter

Ipamorelin

Retatrutide

Cortisol elevation

Negligible vs other GHRPsRaun 1998

—

Prolactin elevation

NegligibleRaun 1998

—

Hunger

Mild appetite increase via ghrelin-receptor crosstalk

—

Injection site reaction

Mild irritation possible

—

GH excess (overdose)

Joint pain, edema, insulin resistance

—

IGF-1 elevation

Dose-dependent; monitor with chronic high-dose use

—

Cancer risk

Theoretical via GH/IGF-1 axis; contraindicated in active malignancy

—

Pregnancy / OB

Avoid

Avoid (insufficient data)

GI symptoms

—

Nausea, vomiting, diarrhea (very common, dose-dependent)Jastreboff 2023

Heart rate

—

↑ resting HR (3–7 bpm at 12 mg)Jastreboff 2023

Glucose handling

—

Glycemic improvement; rare hyperglycemia from glucagon component

Pancreatitis risk

—

Class warning

Thyroid C-cell tumours

—

Class warning (presumed)

Absolute Contraindications

Ipamorelin

·Active malignancy or cancer history
·Pregnancy / breastfeeding
·Disrupted hypothalamic-pituitary axis

Retatrutide

·MTC personal or family history (presumed class effect)
·Pregnancy / breastfeeding

Relative Contraindications

Ipamorelin

·Untreated diabetes
·Severe insulin resistance
·Concurrent corticosteroid use (theoretical desensitisation)

Retatrutide

·Severe gastroparesis
·History of pancreatitis
·Severe cardiovascular disease (HR signal)

05Administration Protocol

Parameter

Ipamorelin

Retatrutide

1. Reconstitution

Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL. Roll gently. Solution should be clear.

Investigational peptide. Research vials reconstituted with bacteriostatic water per label.

2. Injection site

Subcutaneous, abdomen or thigh. Rotate sites. Pinch fat for shallow SQ delivery.

SQ — abdomen, thigh, or upper arm. Rotate weekly.

3. Timing

Pre-sleep optimal — aligns with natural GH pulse. Some protocols add a morning fasted dose.

Once weekly, same day.

4. Storage

Lyophilised: room temp, protected from light. Reconstituted: refrigerate 2–8 °C, use within 30 days.

Refrigerate 2–8 °C. Light-protected.

5. Needle

29–31G, 4–8 mm insulin syringe.

27–31G, 4–8 mm insulin syringe.

06Stack Synergy

Ipamorelin

+ Tesamorelin

Strong

View Tesamorelin →

Ipamorelin (GHRP) + tesamorelin (GHRH analogue) is the textbook dual-axis GH stack. They activate two distinct pituitary receptors — the ghrelin receptor and the GHRH receptor — producing a synergistic GH pulse larger than either alone. Ipamorelin's selectivity (no cortisol/prolactin spike) makes it the ideal GHRP partner for long-term protocols.

Ipamorelin: 200–300 mcg SQ · pre-sleep
Tesamorelin: 2 mg SQ · same injection · pre-sleep
Primary benefit: Maximal GH pulsatility, fat loss, recovery, sleep depth

Raun 1998 Bowers 2002

+ CJC-1295 (no DAC)

Strong

View CJC-1295 (no DAC) →

CJC-1295 (no DAC) is a short-acting GHRH analogue. Combined with ipamorelin (GHRP), the pulse is amplified across both receptor systems with timing similar to native physiology. Without the DAC modification, the stack maintains sharp peaks rather than the sustained elevation seen with CJC-1295-DAC + ipamorelin.

Ipamorelin: 200–300 mcg SQ · pre-sleep
CJC-1295 (no DAC): 100 mcg SQ · same injection
Primary benefit: Pulsatile GH stimulation matching physiological pattern

Teichman 2006 Ionescu 2006

Retatrutide

— no documented stacks