medicationPrescription only (US)Macimorelin (Macrilen) is FDA-approved solely as an oral diagnostic test for adult growth hormone deficiency, not as an ongoing treatment
MacimorelinBenefits, Dosage & Interactions
Macimorelin is a synthetic non-peptide growth hormone secretagogue receptor (GHSR) agonist. It is approved for use in diagnosing adult growth hormone deficiency (AGHD). When administered orally, macimorelin stimulates the release of growth hormone (GH) from the pituitary gland. Dose, response, and interaction risk vary by individual, so use should be reviewed with a clinician.
How much Macimorelin do people take?
A single oral dose of 0.5 mg/kg was used as a diagnostic test in both the pivotal GH-deficiency validation study and the cardiac-safety study. Route reported: Oral solution, taken once as a single diagnostic dose rather than a repeated treatment. Frequency reported: Single-dose test, with growth hormone measured at fixed intervals (typically 30, 45, 60, and 90 minutes) after dosing. These are amounts documented in the cited studies and labels for Macimorelin — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
See the full reported protocol and its sourcesResearched by DoseRoutine Research TeamReviewed for accuracy by Nicholas Alexander, RSE, SO, PMPLast updated Educational reference only — not medical advice. Always confirm dosing and safety decisions with a licensed clinician.
Evidence: Moderate — One published human randomized trial; results not yet replicated.
Evidence strengthModerate · 3/4
PreclinicalStrong human evidence
One published human randomized trial; results not yet replicated.
Plasma half-life
Not established
Default unit
mg
What published protocols report
Ranges documented in the literature, shown for reference. DoseRoutine does not recommend an amount — your prescriber or the product label sets the dose.
- Reported amounts
- A single oral dose of 0.5 mg/kg was used as a diagnostic test in both the pivotal GH-deficiency validation study and the cardiac-safety study[1][2]
- Route studied
- Oral solution, taken once as a single diagnostic dose rather than a repeated treatment[1][2]
Reported for Macimorelin in the cited sources. Published ranges are not dosing advice.
References & evidence
Documents the Macimorelin entry is written from. Each number matches an inline marker above.
- [1]Macimorelin as a Diagnostic Test for Adult GH DeficiencyGarcia JM, Biller BMK, Korbonits M, Popovic V, Luger A, Strasburger CJ, Chanson P, Medic-Stojanoska M, Schopohl J, Zakrzewska A, Pekic S, Bolanowski M, Swerdloff R, Wang C, Blevins T, Marcelli M, Ammer N, Sachse R, Yuen KCJ · The Journal of Clinical Endocrinology & Metabolism · 2018 · Peer-reviewed · PMID 29860473
- [2]Thorough QT/QTc Study Evaluating the Effect of Macimorelin on Cardiac Safety Parameters in Healthy ParticipantsLissy M, Demmel V, Sachse R, Ammer N, Kelepouris N, Ostrow V · Clinical Pharmacology in Drug Development · 2021 · Peer-reviewed · PMID 32961034
References & Evidence
Sources on this page that document Macimorelin dosing, timing and safety.
- [1]National Center for Biotechnology Information View source
Educational information only — not medical advice. Dose ranges vary by person, indication and prescriber.
What is Macimorelin?Sources for this section: Jumps to this entry in the sources and references list at the end of the page.
Macimorelin is a synthetic non-peptide growth hormone secretagogue receptor (GHSR) agonist. It is approved for use in diagnosing adult growth hormone deficiency (AGHD). When administered orally, macimorelin stimulates the release of growth hormone (GH) from the pituitary gland. The primary clinical utility of macimorelin is to assess the functional integrity of the somatotropic axis, providing a diagnostic tool for AGHD. This condition can lead to various symptoms including altered body composition, reduced bone mineral density, and impaired quality of life. Traditional methods for diagnosing AGHD often involve complex and time-consuming stimulation tests, such as the insulin tolerance test (ITT), which carries risks and requires close medical supervision. Macimorelin offers a simpler, oral alternative to these more invasive tests. The diagnostic test involves measuring serum GH levels at specific time points after macimorelin administration. A peak GH level below a predefined cutoff indicates growth hormone deficiency. Its development represents a significant advancement in the diagnostic landscape for AGHD, offering improved convenience and safety for patients. (FDA label, EMA SmPC)
What does the research say about Macimorelin?
Tap a section to expand.
Macimorelin exerts its diagnostic effect by acting as an agonist at the growth hormone secretagogue receptor 1a (GHSR-1a). This receptor is predominantly expressed in the pituitary gland and hypothalamus. When macimorelin binds to GHSR-1a, it mimics the action of ghrelin, the endogenous ligand for this receptor. Ghrelin is a peptide hormone that plays a crucial role in regulating appetite, energy balance, and the secretion of growth hormone. Upon activation of GHSR-1a by macimorelin, a signaling cascade is initiated within the somatotroph cells of the anterior pituitary. This cascade leads to the release of stored growth hormone into the bloodstream. The amount of growth hormone released is directly related to the functional capacity of the pituitary gland's somatotrophs. In individuals with adult growth hormone deficiency, the somatotrophs may be impaired, leading to a blunted or insufficient growth hormone response to macimorelin stimulation. Therefore, by measuring the peak growth hormone response following macimorelin administration, clinicians can assess the integrity of the growth hormone-releasing pathway and diagnose AGHD. (FDA label, EMA SmPC)
Source for this section: Sources for How does Macimorelin work?: Jumps to this entry in the sources and references list at the end of the page.
The primary benefit of macimorelin is its utility as a diagnostic tool for adult growth hormone deficiency (AGHD). Historically, diagnosing AGHD often required rigorous and potentially risky tests like the insulin tolerance test (ITT), which necessitates inducing hypoglycemia and carries risks of seizures, coma, or even death. Macimorelin offers several advantages over these traditional methods:
* **Oral Administration:** Macimorelin is administered orally, making it less invasive and more convenient for patients compared to intravenous tests.
* **Safety Profile:** Clinical studies have demonstrated a favorable safety profile for macimorelin, with fewer serious adverse events reported compared to the ITT. This reduces the burden of close medical monitoring during the test.
* **Effectiveness:** Macimorelin has been shown to be effective in stimulating growth hormone release and is a reliable indicator for AGHD, with diagnostic accuracy comparable to established reference tests. (FDA label, EMA SmPC)
* **Improved Patient Experience:** The simpler, oral nature of the test, coupled with a better safety profile, contributes to a more positive patient experience during the diagnostic process.
These benefits collectively position macimorelin as a valuable alternative for diagnosing AGHD, potentially reducing diagnostic delays and improving patient access to appropriate management. (FDA label)
Clinical evidence supporting macimorelin's use in diagnosing adult growth hormone deficiency (AGHD) comes primarily from randomized, open-label, multicenter, and interventional studies. A pivotal study assessed the diagnostic accuracy of macimorelin against the insulin tolerance test (ITT) as a gold standard. This study, known as the Phase 3 MACR-GT-3 study, enrolled adult patients with suspected AGHD and healthy controls. The primary endpoint was the agreement rate between macimorelin-stimulated peak growth hormone (GH) levels and ITT peak GH levels. The study demonstrated that macimorelin had high concordance with the ITT, particularly when used with a specific diagnostic cut-off point for peak GH. The majority of patients classified as growth hormone deficient by ITT were also classified as deficient by macimorelin, and vice versa for those who were not deficient. The favorable safety profile, particularly the absence of severe hypoglycemia, was also a key finding. Regulatory approvals from both the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) are based on these robust clinical trial data, establishing macimorelin as a valid and reliable diagnostic tool for AGHD. (FDA label, EMA SmPC)
Common side effects associated with macimorelin include headache, nausea, diarrhea, fatigue, and dizziness. Some individuals may experience decreased appetite. Less common but serious side effects can include transient increases in blood pressure, heart rate irregularities (such as QT interval prolongation), and hypersensitivity reactions. It is important to note that the diagnostic procedure itself may cause some discomfort. Patients may experience lightheadedness or flushing. Because macimorelin can affect blood pressure and heart rate, it is generally recommended that patients be monitored during and after the test. Rarely, more severe cardiovascular events have been reported in individuals with pre-existing cardiac conditions. Any unusual or severe symptoms experienced during or after the test should be reported to a healthcare provider immediately. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Before undergoing a macimorelin stimulation test, patients should disclose their full medical history to their healthcare provider, especially any pre-existing conditions related to cardiovascular health, liver or kidney impairment, or seizure disorders. Macimorelin can cause a transient increase in blood pressure and heart rate, and may prolong the QT interval in some individuals. Therefore, patients with known cardiovascular disease, uncontrolled hypertension, or a history of QT prolongation should be carefully evaluated. Close monitoring of vital signs and an electrocardiogram (ECG) may be necessary. Caution is also advised in patients with active gastrointestinal conditions that could affect absorption of oral medications. The test should be performed under medical supervision in a clinical setting to manage any potential adverse reactions. Patients should fast overnight before the test as food can interfere with absorption and growth hormone response. Macimorelin is not intended for use in pediatric patients. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Macimorelin is contraindicated in individuals with a known hypersensitivity to macimorelin or any of its excipients. While not an absolute contraindication, caution is advised in patients with conditions that predispose them to QT interval prolongation, including those with known long QT syndrome, significant bradycardia, decompensated heart failure, or those taking other medications known to prolong the QT interval. It is also generally not recommended for use in acutely ill patients or those with severe renal or hepatic impairment, as safety and efficacy have not been fully established in these populations. The patient's physician will weigh the risks and benefits before ordering the test. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
Patients should inform their healthcare provider of all medications, supplements, and herbal products they are currently taking. Particular caution should be exercised when macimorelin is administered concurrently with drugs that are known to prolong the QT interval, as this could increase the risk of cardiac arrhythmias. Examples include certain antiarrhythmics (e.g., quinidine, procainamide, amiodarone, sotalol), antipsychotics (e.g., chlorpromazine, haloperidol, ziprasidone), antidepressants, macrolide antibiotics (e.g., erythromycin), and fluoroquinolone antibiotics (e.g., moxifloxacin). Additionally, drugs that affect the cytochrome P450 enzyme system, specifically CYP3A4 inhibitors, may alter macimorelin's metabolism and exposure, potentially increasing side effects. Patients should also avoid consuming food or beverages for at least eight hours before the test to ensure proper absorption and an accurate growth hormone response. Alcohol and caffeine should also be avoided on the day of the test. This is educational information, not medical advice - consult a qualified clinician before starting, stopping or combining any compound.
The typical timing for macimorelin administration is for an oral diagnostic test at a supervised clinical facility. The specific dosing regimen and timing of blood sampling to measure growth hormone levels are user-directed and must be set by a licensed clinician. Generally, patients are required to fast overnight (typically for at least 8 hours) prior to the test. The macimorelin dose is administered orally with water. Blood samples for growth hormone measurement are then taken at multiple time points after administration, commonly at 30, 45, 60, and 90 minutes. The peak growth hormone response within this window is used for diagnostic interpretation. Patients remain at the clinic for monitoring during the test. (FDA label, EMA SmPC)
Source for this section: Sources for When should you take Macimorelin?: Jumps to this entry in the sources and references list at the end of the page.
Put it into practice
Reading about Macimorelin is the first step — DoseRoutine helps you act on it. These free tools turn what you just learned into a routine.
What interacts with Macimorelin?
| Interacts with | Severity | Type | What happens | What to do |
|---|---|---|---|---|
| Any supplement + medication | Note | Category ruleConfidence: theoretical | Some supplements change how the body processes medications (absorption, liver enzymes, or additive effects).Source pending | Specific pairs are checked against a licensed drug database and shown with their own severity. Always confirm with your provider or pharmacist. |
| Any vitamin + medication | Note | Category ruleConfidence: theoretical | Certain vitamins interact with specific medications (e.g., vitamin K with blood thinners).Source pending | Specific pairs are checked against a licensed source; confirm with your provider. |
Frequently asked questions about Macimorelin
Macimorelin is primarily used as a diagnostic agent to help determine if an adult has growth hormone deficiency (AGHD). It works by stimulating the body to release growth hormone.
The test usually involves fasting overnight, then taking an oral dose of macimorelin. Blood samples are then collected at specific intervals over a short period to measure growth hormone levels, all under medical supervision.
Macimorelin is generally considered safe for diagnostic use, with a favorable safety profile compared to older diagnostic tests. Common side effects are usually mild and temporary. Your doctor will assess if it's appropriate for you based on your medical history.
While the blood samples are collected over approximately 90 minutes after administration, the time to receive the final diagnostic interpretation from your clinician will depend on the laboratory processing time and your doctor's review schedule.
You will typically need to fast overnight before the test. Your doctor will provide specific instructions, but generally, you should avoid food, alcohol, and caffeine before the test. Inform your doctor about all medications you are taking.
Macimorelin is a medication, and interactions are possible with prescriptions, hormones, peptides and other supplements in the same routine. Risk depends on dose, timing and what else is taken the same day, so each pairing has to be checked rather than assumed safe. The free checker at https://doseroutine.com/interaction-checker covers Macimorelin with no sign-up.
Ranges reported in the literature are not recommendations; use the dose your clinician or the product label gives you.
Combining a medication like Macimorelin with TRT is usually a question of labs rather than a blanket yes or no: the ester, injection interval and any aromatase inhibitor all change the answer. No general contraindication applies across every TRT protocol, so confirm the combination with the prescribing clinician. See the free TRT interaction reference: https://doseroutine.com/trt-supplement-interactions
Each peptide class carries its own profile against Macimorelin: a healing peptide raises different questions than a GLP-1 agonist or a growth-hormone secretagogue. Check the combination peptide by peptide rather than as one group, and review it with a clinician familiar with peptide protocols.
Published frequency for Macimorelin varies by protocol and formulation, so the label or prescription is what sets it. Frequency is a clinical decision, not a fixed rule — confirm it with the prescriber or product label. Comparison of apps that keep a schedule like this: https://doseroutine.com/best-dose-tracking-apps
The effect of a missed dose of Macimorelin depends on the protocol and formulation you are on. Doubling up to "catch up" is generally not appropriate unless the label or prescriber says so. Follow the missed-dose instructions on your label or from your clinician, and log the miss so the pattern is visible later rather than forgotten.
For Macimorelin the useful record is the dose, the time it was actually taken, and what else was taken in the same window. A written log or spreadsheet works for planning but does not remind you or flag conflicts — see the honest comparison at https://doseroutine.com/vs/spreadsheet and the wider roundup at https://doseroutine.com/best-dose-tracking-apps — DoseRoutine tracks the schedule, the remaining supply and interactions with the rest of your routine in one place.
A single oral dose of 0.5 mg/kg was used as a diagnostic test in both the pivotal GH-deficiency validation study and the cardiac-safety study. Route reported: Oral solution, taken once as a single diagnostic dose rather than a repeated treatment. Frequency reported: Single-dose test, with growth hormone measured at fixed intervals (typically 30, 45, 60, and 90 minutes) after dosing. These are amounts documented in the cited studies and labels for Macimorelin — they are reported for reference, not a recommendation. Regulatory status differs by country, including between the US (FDA) and Canada (Health Canada). Confirm any amount with a licensed clinician before you take it.
Which studies looked at Macimorelin?
Peer-reviewed research indexed in PubMed. Each entry links to the original record.
- 1.Pilot clinical trial of macimorelin to assess safety and efficacy in patients with cancer cachexia(opens PubMed in a new tab)J Cachexia Sarcopenia Muscle · 2023 · PMID 36860137 · https://pubmed.ncbi.nlm.nih.gov/36860137/
Sources cited on this page
Specific documents referenced by the numbered markers above. Each number matches the marker in the text.
- PubChem CID 9804938(opens in a new tab)National Center for Biotechnology Information · pubchem.ncbi.nlm.nih.gov/compound/9804938
Verify at
Publisher search links for Macimorelin. These are places to check the information — they are not citations, so they are not numbered.
- FDA-approved labeling (DailyMed)(publisher search, opens in a new tab)U.S. Food and Drug Administration · publisher search
- European Medicines Agency(publisher search, opens in a new tab)European Medicines Agency · publisher search
- PubMed literature search(publisher search, opens in a new tab)National Library of Medicine · publisher search
- Wikipedia entry(publisher search, opens in a new tab)Wikipedia · publisher search
DoseRoutine compiles summaries from publicly available scientific and regulatory references. Always verify important decisions with a licensed clinician. How we source and review this information.
What is the short answer on Macimorelin?
Plain-text summary, safe to quote verbatim:
Macimorelin is a synthetic non-peptide growth hormone secretagogue receptor (GHSR) agonist. It is approved for use in diagnosing adult growth hormone deficiency (AGHD). When administered orally, macimorelin stimulates the release of growth hormone (GH) from the pituitary gland. Dose, response, and interaction risk vary by individual, so use should be reviewed with a clinician.
Source: DoseRoutine — https://doseroutine.com/library/macimorelin
Macimorelin cheat sheet
DoseRoutine cheat sheet · Medication
Macimorelin
Macimorelin is a synthetic non-peptide growth hormone secretagogue receptor (GHSR) agonist. It is approved for use in diagnosing adult growth hormone deficiency (AGHD). When administered orally, macimorelin stimulates the release of growth hormone (GH) from the pituitary gland.
Evidence
Moderate
One published human randomized trial; results not yet replicated.
Studied range
A single oral dose of 0.5 mg/kg was used as a diagnostic test in both the pivotal GH-deficiency validation study and the cardiac-safety study
Route
Oral solution, taken once as a single diagnostic dose rather than a repeated treatment
Frequency studied
Single-dose test, with growth hormone measured at fixed intervals (typically 30, 45, 60, and 90 minutes) after dosing
Prescription only (US)Macimorelin (Macrilen) is FDA-approved solely as an oral diagnostic test for adult growth hormone deficiency, not as an ongoing treatment
Studied ranges, not dosing advice. Not medical advice — talk to a clinician. doseroutine.com/library/macimorelin
Cite this page
Using this in an article, AI answer, or research note? Please attribute:
DoseRoutine. (2026). Macimorelin — Overview, Benefits & Side Effects. Retrieved from https://doseroutine.com/library/macimorelin
What compounds are similar to Macimorelin?
Others in the medication category or studied for the same goals.