Ipamorelin: Selective Ghrelin-Receptor Agonist, Dosage Frameworks, and Side Effects

Ipamorelin is a synthetic five-amino-acid peptide that stimulates growth hormone release by activating the ghrelin receptor in the pituitary and hypothalamus. It belongs to the growth hormone releasing peptide (GHRP) class, alongside GHRP-2, GHRP-6, and hexarelin, and it is best known for one property: selectivity. In preclinical studies, ipamorelin released growth hormone without the marked increases in cortisol, ACTH, and prolactin seen with earlier GHRPs. This page covers what ipamorelin is, how it works, what the evidence shows, dosing frameworks, side effects, and regulatory status.

What Is Ipamorelin?

Structure

Ipamorelin is a pentapeptide containing non-natural amino acids — Aib-His-D-2-Nal-D-Phe-Lys-NH2 — designed to resist breakdown and to bind the growth hormone secretagogue receptor. It was developed in the 1990s in a pharmaceutical research program aimed at finding GH secretagogues with cleaner hormonal profiles than the first-generation GHRPs.

Development History

Ipamorelin reached human clinical testing. Pharmacokinetic studies in healthy volunteers characterized a short plasma half-life, in the range of a couple of hours, and a dose-dependent GH response. It was later investigated as a treatment for postoperative ileus, a gut-motility indication that draws on ghrelin's effects on the GI tract. Those trials did not lead to approval, and ipamorelin has never been an FDA-approved drug.

How Ipamorelin Works

Ghrelin-Receptor Agonism

Ipamorelin binds the growth hormone secretagogue receptor type 1a (GHS-R1a), the receptor for the hunger hormone ghrelin. In the pituitary, activation of this receptor triggers GH release through a pathway separate from the GHRH receptor. At the hypothalamic level, ghrelin-receptor signaling also increases GHRH release and reduces somatostatin's inhibitory tone.

Why Selectivity Matters

Earlier GHRPs stimulate GH but also raise cortisol and prolactin, and GHRP-6 in particular strongly increases appetite. In animal studies, ipamorelin showed GH-releasing potency comparable to GHRP-6 without the corresponding rise in ACTH and cortisol, and its appetite effects appear milder. For patients who are not seeking appetite stimulation, and for clinicians who want to avoid stacking a cortisol signal on top of GH, that profile is the reason ipamorelin is often chosen within the class.

We compare GHRP-2 and GHRP-6 in more depth in GHRP-2 vs GHRP-6.

Pairing With a GHRH Analogue

Because ghrelin-receptor agonists and GHRH analogues act through different receptors, the two classes are often combined; the GH pulse from both together is larger than from either alone. That combination is the subject of our CJC-1295 + ipamorelin page. Ipamorelin is also compared directly with the GHRH analogue sermorelin in Sermorelin vs Ipamorelin.

What the Research Shows

Established

• GH release. Ipamorelin produces a dose-dependent GH response in animals and humans.
• Selectivity. Preclinical work consistently shows less effect on ACTH and cortisol than other GHRPs.
• Tolerability in short-term human studies. Clinical studies, including the postoperative ileus program, did not surface major safety signals over their short durations.

Studied, With Limited Human Data

• Body composition, recovery, and sleep. These effects follow plausibly from increased GH and IGF-1 and are widely reported in clinical practice, but there are no large, long-term human trials of ipamorelin for these outcomes.
• Bone. Animal studies have reported effects on bone growth and density through the GH/IGF-1 axis; human data are lacking.

The honest summary: ipamorelin's pharmacology is well characterized, and its long-term outcome data are not.

Ipamorelin Dosage Frameworks

Ipamorelin is not an FDA-approved drug and has no labeled dose. The frameworks below describe how protocols are typically structured; specific dose amounts are set by the prescriber and should be confirmed against the compounding partner's formulation.

• Route. Subcutaneous injection is the reference route. Oral spray, sublingual, and nasal formulations exist but deliver less of each nominal dose; see our comparison of delivery methods.

• Frequency. Because the half-life is short, protocols typically use once-daily dosing or divided doses rather than weekly injections.
• Timing. Doses are commonly given at bedtime, to align with the natural nocturnal GH pulse, and away from meals. Carbohydrate, insulin, and circulating fatty acids blunt GH release, so dosing on an empty stomach tends to produce a larger response.
• Titration. IGF-1 is measured at baseline and after several weeks. Dose adjustments aim to keep IGF-1 within the age-adjusted reference range.
• Duration and cycling. Protocols commonly run in blocks of weeks to months, with periodic reassessment; some clinicians cycle off to limit receptor desensitization, which is well described for the more potent GHRPs.
• Reconstitution. Ipamorelin is supplied as a lyophilized powder. Our peptide reconstitution calculator converts vial strength and diluent volume into syringe units, and how to reconstitute peptides walks through the process.

When ipamorelin is used with a GHRH analogue, the combined schedule is covered in our CJC-1295 and ipamorelin dosing guide.

Ipamorelin Side Effects

Short-term tolerability is generally reported as good. Effects described in studies and clinical practice include:

• Injection-site reactions — redness, itching, or mild swelling.
• Headache and flushing, usually transient.
• Increased hunger, typically milder than with GHRP-6.
• Dizziness or lightheadedness shortly after dosing.
• GH-related effects with sustained elevation: fluid retention, joint aches, and tingling or numbness in the hands. These are signs that GH or IGF-1 may be running too high and call for reassessment.
• Glucose effects. GH opposes insulin action, so fasting glucose and HbA1c are reasonable to follow in patients with insulin resistance or prediabetes.

Standard precautions for GH-axis stimulation apply: active malignancy, pregnancy, and uncontrolled diabetes are common reasons not to proceed.

Ipamorelin, Appetite, and Metabolism

Because ipamorelin acts on the ghrelin receptor, questions about hunger and metabolism come up often. Ghrelin itself is a potent appetite signal, and GHRP-6 reproduces that effect strongly. Ipamorelin's appetite effect appears milder, though some patients notice increased hunger, particularly early in a protocol.

Growth hormone raises lipolysis and reduces insulin sensitivity. For most patients the net metabolic effect of a well-titrated protocol is modest, but patients with insulin resistance, prediabetes, or diabetes warrant glucose monitoring. Protocols that time ipamorelin away from meals avoid food blunting the GH response and keep the injection separate from the post-meal insulin rise.

Patient Selection and Monitoring

Clinicians typically consider ipamorelin for adults with an intact pituitary, symptoms or laboratory findings consistent with declining GH/IGF-1 output, and goals that fit the GH axis — body composition, recovery, and sleep quality. Common reasons not to proceed include active malignancy, pregnancy, uncontrolled diabetes, and competitive sport subject to anti-doping rules.

Regulatory Status

The FDA removed specific salt forms of ipamorelin from Category 2 in April 2026 (see our April 2026 Category 2 update), and our FDA peptide status tracker lists ipamorelin in Category 1 — under evaluation. Category 1 substances may generally be used in 503A compounding while the review continues, but the designation is interim and applies to the specific nominated form. Check the tracker for current status.

Ipamorelin, like all GH secretagogues, is prohibited at all times under the WADA Prohibited List.

Where Ipamorelin Fits

Ipamorelin is one of several growth hormone peptides. How it compares with GHRH analogues like sermorelin and tesamorelin, and how those peptides fit with training and nutrition, is covered in our hub on peptides for muscle growth.

Newtropin does not prescribe or compound. We connect licensed providers with a licensed 503A compounding partner; prescribers can start at For Providers.

This page is educational content for licensed healthcare professionals and is not medical advice.

Frequently Asked Questions

What is ipamorelin?

Ipamorelin is a synthetic pentapeptide that activates the ghrelin receptor (GHS-R1a) to stimulate growth hormone release. It is a member of the growth hormone releasing peptide class, known for its selectivity.

What makes ipamorelin different from other GHRPs?

In preclinical studies, ipamorelin released growth hormone without the notable increases in cortisol, ACTH, and prolactin seen with GHRP-2, GHRP-6, and hexarelin, and with milder appetite stimulation.

How is ipamorelin dosed?

Ipamorelin has no FDA-labeled dose. Protocols typically use subcutaneous injection once daily or in divided doses, often at bedtime and away from meals, with the dose set by the prescriber and adjusted based on IGF-1.

What are the side effects of ipamorelin?

Commonly reported effects are injection-site reactions, headache, flushing, mild hunger, and dizziness. Fluid retention, joint aches, or hand tingling suggest GH or IGF-1 may be too high.

Is ipamorelin FDA-approved?

No. It reached clinical trials but was never approved. Our FDA tracker lists it in Category 1 (under evaluation) for 503A compounding.

Is ipamorelin the same as CJC-1295?

No. CJC-1295 is a GHRH analogue and ipamorelin is a ghrelin-receptor agonist. They act through different receptors, which is why they are often prescribed together.