Sermorelin: Doses, Routes, and Half-Life in the Research Literature

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This page reports the sermorelin doses, routes, and pharmacokinetics that appear in published studies — and nothing more. It does not tell anyone how much to take. Peptides like sermorelin were given by injection under the skin in trials; the page also explains why the molecule is supplied as a freeze-dried powder and why it clears from the blood in minutes. Read every figure below as "studied at X in population Y," because that is exactly what it is. This is a literature digest, not a course of treatment.

Doses used in the research literature

Across the file, the studied sermorelin dosage figures cluster by purpose, and every one is a study observation rather than a recommendation.

• Pediatric growth-deficiency efficacy: 30 mcg/kg/day subcutaneously at bedtime in growth-hormone-deficient children ^[1].
• Aging research in older men: 0.5 mg and 1 mg subcutaneously twice daily for 14 days, which produced dose-related GH and IGF-1 increases ^[2].
• Diagnostic GHRH stimulation: a single intravenous bolus (commonly ~1 mcg/kg) historically used to test pituitary growth-hormone reserve.
• Pharmacokinetic study: intravenous doses of 0.25-2 mcg/kg elicited growth-hormone release in healthy men, with maximal release at 1-2 mcg/kg ^[3].

The pattern across these is consistent. Sermorelin was dosed to a body-weight amount (mcg/kg) or a fixed-milligram amount, given by injection, on an intermittent schedule — never a continuous drip — which matches the pulsatile mechanism described on the GHRH(1-29) research record ^[12]. The figures also span very different purposes: a once-daily growth dose in children, a twice-daily research dose in older men, and a single bolus for diagnostic or pharmacokinetic testing ^[1][2][3]. Reading any one of them as a personal protocol would ignore the population and purpose it was studied in. None of these figures is a recommendation; each is a study observation, and this page reports them as exactly that.

Sermorelin half-life

Native GHRH(1-29) has a short plasma half-life on the order of ~10-12 minutes after intravenous administration — it is rapidly eliminated ^[3]. Yet a single dose elevates serum growth hormone for roughly 3 hours, because the peptide triggers a pulse that outlasts its own presence in the blood ^[3]. The distinction is worth holding onto: the half-life describes how long the drug stays in circulation, while the ~3-hour growth-hormone elevation describes how long the downstream effect lasts. They are not the same number, and conflating them is a common error.

That brevity also fits the mechanism rather than fighting it. The pituitary reads a pulsatile signal; a short-lived peptide delivers exactly that — a discrete burst rather than a sustained occupancy of the receptor ^[12]. Pulsatile GHRH delivery preserved growth-hormone responsiveness better than a continuous infusion in normal men, which suggests the brief signal is a feature of the native system, not merely a pharmacokinetic limitation ^[12].

Still, the short half-life is the design constraint behind the whole longer-acting-analog field. The native peptide's brevity motivated stabilized analogs — the D-Ala2 substitution and the DAC (Drug Affinity Complex) albumin-binding technology behind CJC-1295, and the stabilized analog tesamorelin used in the cognition and body-composition trials ^[3][14]. The trade-off is mechanistic: a longer half-life moves away from the brief, pulse-like native signal toward a more sustained stimulus, which is a different pharmacology, not strictly a better one.

Routes studied

Three routes appear in the literature, with sharply different bioavailability. Subcutaneous injection is the primary studied route — used in the pediatric efficacy trial and the older-men aging study ^[1][2]. Intravenous dosing appears in the diagnostic and pharmacokinetic work ^[3]. Intranasal administration was examined historically but reached a bioavailability of only ~3-5% ^[3], which is why mucosal, oral, sublingual, and troche "sermorelin" formulations are widely criticized in research-user communities as poorly absorbed — peptides are degraded in the gut and cross mucosa inefficiently. The bioavailability number is the simplest reason the injectable route dominates the studied record.

Sermorelin acetate

The compound is supplied as sermorelin acetate — the acetate salt of GHRH(1-29), a lyophilized (freeze-dried) powder. Lyophilization exists because aqueous peptide solutions degrade: GHRH(1-29) is supplied dry and reconstituted with sterile diluent when needed, after which it is typically refrigerated. The molecule is the amidated 29-residue N-terminal fragment of GHRH, molecular weight 3357.9 Da, CAS 86168-78-7 — defined chemistry, which is part of why a 29-amino-acid fragment was chosen over the full 44-residue hormone ^[14].

The salt and powder facts also explain the route picture covered above. A peptide fragile enough to require freeze-drying for storage is, unsurprisingly, poorly suited to the gut, which is consistent with the very low ~3-5% intranasal bioavailability reported for GHRH(1-29) and the poor regard for oral and sublingual formulations ^[3]. Compounded preparations are prepared under USP <797> sterile-compounding standards, reflecting sermorelin's present status as a Category 1 bulk drug substance under FDA's interim Section 503A policy. The acetate salt, the lyophilized form, and the compounding standard are handling, stability, and regulatory facts about the material — not dosing guidance, and not a recommendation to obtain or use it.

Why is it recommended to inject sermorelin at night?

Endogenous growth hormone is secreted in pulses concentrated during slow-wave sleep, so bedtime administration in studies aligned GHRH stimulation with the body's natural nocturnal growth-hormone pulse ^[12]. This describes study protocols — the pediatric trial and the cognition trial both dosed at bedtime ^[1][6] — not a personal dosing instruction.

When is the best time to take sermorelin?

Studies typically administered GHRH-axis stimulation at bedtime to coincide with natural nocturnal, slow-wave-sleep growth-hormone pulses ^[1][6][12]. This reflects research protocols and is not a personal dosing recommendation.