CJC-1295 with DAC has one of the longest documented half-lives among growth hormone-releasing peptides, at approximately 5.8–8.1 days in humans. CJC-1295 without DAC, on the other hand, has no published dedicated human half-life study. Understanding this difference explains almost everything else about how the two versions are used and discussed differently.
The half-life of CJC-1295 is 7-10 days.
The half-life refers to the time it takes for half of a given dose of a substance to be eliminated from the bloodstream. It is a central concept for understanding how often a compound needs to be dosed to maintain a consistent effect. For CJC-1295 with DAC – a version that has been directly studied in human trials – researchers measured a half-life of approximately 5.8–8.1 days, following single escalating doses in healthy adults. This number comes from standard pharmacokinetic analysis within that study [1]. This is an extremely long half-life for a peptide. It is specifically due to the DAC (Drug Affinity Complex) modification. This allows the peptide to form a covalent bond with serum albumin, the most abundant protein in the blood. This bond protects it from rapid breakdown and kidney filtration, which would otherwise clear it from circulation within minutes or hours [2].
For CJC-1295 without DAC, no dedicated human pharmacokinetic study measuring its half-life has been identified in the peer-reviewed literature accessed for this article. As this version entirely lacks the albumin-binding mechanism, its half-life would be expected – based on structural similarity to native growth hormone releasing hormone – to be measured in minutes rather than days. However, this is a reasonable conclusion drawn from chemistry, not a number confirmed by a dedicated clinical study of the DAC-free compound itself. This distinction should not be presented as established fact.
CJC-1295 DAC half-life – why does it matter?
The practical significance of CJC-1295 DAC’s multi-day half-life becomes clear when we look at how it was actually used in the human study that established it. Because the compound stays in the bloodstream for days, rather than hours, the study’s dosing schedules for repeated administration used weekly or bi-weekly injections, rather than daily dosing. This schedule was sufficient to elicit a cumulative effect on IGF-1, with levels remaining elevated for up to 28 days after a short course of doses [1]. This is directly tied to why CJC-1295 DAC is often described in research and commercial contexts as a „long-acting” compound. A half-life measured in days means that the substance does not need to be reintroduced frequently in order to maintain elevated hormone activity. This is fundamentally a different dosing logic than for compounds cleared within minutes.
It's worth being precise here about what. This long half-life describes how long the peptide itself remains present and detectable in the blood. It does not mean that growth hormone or IGF-1 levels remain at their peak the entire time. Separate studies have shown that even during this sustained presence of CJC-1295, the body's natural pulsatile release pattern of growth hormone continued. The main change was a significantly elevated baseline level between pulses, rather than a flat, continuously elevated level [3].
How long does CJC-1295 remain in the body?
Placing the half-life of CJC-1295 into context alongside a related, more commonly recognised compound helps illustrate how remarkable its pharmacokinetic profile is. Sermorelin is an earlier and structurally related GHRH analogue. It was previously FDA approved for diagnostic use in growth hormone deficiency. It has a well-documented human half-life of only about 11–12 minutes, whether given intravenously or subcutaneously. This is derived from pharmacokinetic data summarised in a peer reviewed survey of growth hormone secretagogues [4]. This means that CJC-1295 with DAC remains active in the body approximately 700–1000 times longer than Sermorelin. This difference is entirely attributable to the albumin binding modification of the DAC, and not to any change in the basic amino acid sequence common to both compounds.
Regarding how long CJC-1295 might be detectable by specialised laboratory anti-doping testing, as opposed to how long it remains pharmacologically active, this is a related but distinct question. It was discussed in an earlier article in this series concerning legal status and detectability. Peer-reviewed analytical chemistry studies have developed methods capable of detecting CJC-1295 in urine at concentrations at or below 1 nanogram per millilitre. However, it is important to note that no single, universally applicable „days since last dose” detection window has been established in the literature specifically for the DAC or non-DAC forms [5].
Limitations of current evidence
The half-life for CJC-1295 with DAC – 5.8–8.1 days – is well documented in the primary human pharmacokinetic study for this compound [1]. No equivalent dedicated human pharmacokinetic study for CJC-1295 without DAC, however, has been identified in the literature reviewed here. This means any specific half-life figure given for the DAC-free form elsewhere should be taken as a chemical inference, not a confirmed clinical finding.
Comparisons with the half-life of sermorelin are well supported by separate, well-documented pharmacokinetic data [4]. This article, however, does not extend this comparison to dosing recommendations. As discussed in prior articles in this series, there is no validated consumer dosing protocol for any form of CJC-1295.
Disclaimer
This content is for educational and informational purposes only and should not be interpreted as medical advice or a dosing guide. CJC-1295, both with and without DAC, is a research compound and is not approved by the FDA or the European Medicines Agency for any medical use. The half-life data presented here for the DAC form comes from a single published human pharmacokinetic study, and no equivalent human data exists for the non-DAC form. This information does not constitute a validated dosing schedule.
References
[1] Teichman, S. L., Neale, A., Lawrence, B., Gagnon, C., Castaigne, J. P., & Frohman, L. A. (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology & Metabolism, 91(3), 799–805. https://doi.org/10.1210/jc.2005-1536
[2] Jetté, L., Léger, R., Thibaudeau, K., Benquet, C., Robitaille, M., Pellerin, I., Paradis, V., van Wyk, P., Pham, K., & Bridon, D. P. (2005). Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: Identification of CJC-1295 as a long-lasting GRF analogue. Endocrinology, 146(7), 3052–3058. https://doi.org/10.1210/en.2004-1286
[3] Ionescu, M., & Frohman, L. A. (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analogue. Journal of Clinical Endocrinology & Metabolism, 91(12), 4792–4797. https://doi.org/10.1210/jc.2006-1702
[4] Ishida, J., Saitoh, M., Ebner, N., Springer, J., Anker, S. D., & von Haehling, S. (2020). Growth hormone secretagogues: History, mechanism of action, and clinical development. JCSM Rapid Communications, 3(1), 25–37. https://doi.org/10.1002/rco2.9
[5] Memdouh, S., Gavrilović, I., Ng, K., Cowan, D., & Abbate, V. (2021). Advances in the detection of growth hormone releasing hormone synthetic analogues. Drug Testing and Analysis, 13(11–12), 1871–1887. https://doi.org/10.1002/dta.3183