Last updated 2026-07-26
TL;DR
CJC-1295 comes in two forms with very different half lives. The DAC version lasts about 6 to 8 days in circulation, based on the original pharmacology study. The non-DAC version, often called modified GRF 1-29, has a half life closer to 30 minutes. That single difference drives almost every dosing decision people argue about online.
What is the actual half life of CJC-1295?
It depends entirely on which CJC-1295 you mean, and this is the single most confused point in the whole topic. The compound most people picture when they hear "CJC-1295" is the DAC version, short for Drug Affinity Complex. In the original human pharmacokinetic study, a single subcutaneous dose of CJC-1295 with DAC produced a terminal half life of about 5.8 to 8.1 days, with the paper reporting a mean around 6.8 days depending on dose group [1]. That is an extraordinarily long half life for a peptide, and it's the whole point of attaching the DAC to the molecule in the first place. The other version, sometimes labeled CJC-1295 without DAC, is chemically a different thing: it's essentially modified GRF (1-29), a truncated and stabilized fragment of growth hormone releasing hormone. It has none of the fatty acid chain that binds albumin, so it clears fast. Estimates commonly cited put its half life around 30 minutes, though there isn't a single widely cited human PK paper nailing that number down the way there is for the DAC version. Most of what's out there for the no-DAC form is manufacturer literature and forum consensus, not a peer reviewed study. So when someone asks "what's the half life of CJC-1295," the honest answer is: which one are you asking about, because the numbers differ by roughly 300-fold.
Why does CJC-1295 with DAC last so much longer?
The DAC tag is a maleimide-activated version of a fatty acid derivative that covalently binds to albumin once injected. Albumin is the most abundant protein in blood plasma and it doesn't get cleared or degraded quickly. By hitching a ride on albumin, the peptide avoids the rapid enzymatic breakdown that would otherwise happen to a free peptide in circulation. The researchers who developed this modification were explicit about the goal. The original paper describes CJC-1295 as designed to extend the half life of GRF(1-29) "from minutes to days" through covalent albumin binding, and reports that repeated dosing produced sustained increases in GH and IGF-1 over the study period [1]. This is the same basic trick used in some long-acting insulin and GLP-1 drugs, so it's not an exotic idea. What is worth noting is that this study was small, industry-funded, and now roughly two decades old, and there hasn't been a large modern trial replicating it in the way you'd want for a clinically approved drug.
How does half life affect how often you inject?
Half life is the main reason dosing schedules for the two versions look completely different, at least in the protocols people describe online (none of this is FDA-approved dosing, so all of it comes from secondary sources rather than an approved label). With a half life of roughly 6 to 8 days, DAC-linked CJC-1295 in theory only needs to be injected once or twice a week to maintain elevated blood levels, since it takes about 4 to 5 half lives for a drug to mostly clear, meaning DAC could still have measurable presence in the body for 3 to 4 weeks after a single dose. That long tail is exactly why some protocols space doses out to once weekly. The no-DAC version, with a half life measured in minutes rather than days, gets used very differently. Because it clears almost immediately, it's typically paired with daily or even multiple-times-daily dosing, usually timed around a GH pulse (like before bed or before training) rather than aiming for a sustained blood level. If you want the mechanics of specific schedules, the cjc 1295 dosage page walks through how people structure this, and the cjc-1295 dac dosage calculator is built specifically around the longer DAC half life.
CJC-1295 with DAC vs without DAC: what's the real difference?
| Half life | ~5.8 to 8.1 days [1] | ~30 minutes (commonly cited, not from a major published PK study) | |
|---|---|---|---|
| Mechanism | Covalent albumin binding via DAC tag | Free peptide, rapid clearance | |
| Typical use pattern in secondary sources | 1-2x weekly injections | Daily or multiple daily injections | |
| GH release pattern | Sustained, blunts natural pulsatility | Mimics a natural GH pulse | |
| Clinical trial history | Phase 1/2 trials existed for the parent compound, program discontinued | Not developed as a standalone drug candidate | The blunting of natural pulsatility with the long-acting DAC form is a real physiological concern, more than forum talk. GH normally gets released in pulses, mostly at night, and a peptide that keeps GH secretagogue receptors continuously stimulated works against that pattern. That's one reason a lot of newer secondary source protocols favor the no-DAC form or lower, less-frequent DAC dosing rather than trying to keep blood levels flat all week. For the full comparison of study data behind each version, see cjc 1295 with dac. |
People use "CJC-1295" loosely to mean either compound, which causes a lot of avoidable confusion. Here's a side by side. | Feature | CJC-1295 with DAC | CJC-1295 no-DAC (Mod GRF 1-29) |
Why is CJC-1295 usually paired with ipamorelin?
CJC-1295 is a growth hormone releasing hormone (GHRH) analogue. Ipamorelin is a ghrelin mimetic, also called a growth hormone secretagogue receptor agonist. They work on different receptors that both converge on stimulating the pituitary to release GH, and the rationale for stacking them is dual-receptor amplification: GHRH analogues and ghrelin mimetics have been shown in earlier research to produce a larger GH pulse together than either does alone, because they act through distinct signaling pathways on the somatotroph cell [2]. That receptor-level rationale is genuinely studied, at least for related compound classes; it is not the same as saying the CJC-1295 plus ipamorelin combination itself has been through controlled human trials proving a specific outcome like fat loss or muscle gain. It hasn't, at least not in any large, well-controlled, published trial that this article can point to. What exists is older GHRH/GHRP combined-stimulation literature using different specific molecules, plus a lot of anecdotal protocol-sharing that assumes the combined effect carries over. It probably does carry over to some degree given the shared mechanism, but "probably" is an honest word here, not a settled fact. If you're deciding whether to combine the two, read the mechanism pages rather than assume the pairing is proven for any specific goal: cjc 1295 covers the evidence base directly.
How long does CJC-1295 stay in your system?
For the DAC version, given a half life around 6.8 days on average [1], a rough rule of thumb (4 to 5 half lives to clear roughly 94-97 percent of a drug) puts total clearance somewhere around 27 to 40 days after the last dose. That's a long tail, and it's part of why some people report GH and IGF-1 markers staying elevated for weeks after stopping. For the no-DAC version, with a half life around 30 minutes, it's functionally out of the bloodstream within a few hours of injection. Downstream effects, like any bump in IGF-1, would be short-lived compared to what DAC produces, which is part of the trade-off people are weighing when they choose one form over the other. None of this addresses how long detectable metabolites might persist in urine or how any of this interacts with drug testing, and this article isn't the place to speculate on that; if that matters to you, that's a question for a toxicologist or the specific testing body involved, not a peptide blog.
Does a longer half life mean more side effects?
Not automatically, but a longer half life does mean less room to course-correct if something goes wrong, since the compound is going to keep acting for weeks regardless of what you decide the day after injecting. The original DAC study reported that repeated weekly dosing over extended periods sustained elevated IGF-1 levels without shutting them down between doses, which was the intended effect [1]. But sustained, non-pulsatile GH/IGF-1 elevation is a different physiological state than the body's normal nightly pulse pattern, and long-term human safety data on that specific pattern, in the population actually using compounded CJC-1295, doesn't really exist in peer-reviewed form. Reported issues in the secondary literature and case reports for GH secretagogues broadly include injection site reactions, water retention, and effects on blood glucose and insulin sensitivity, but attributing any of that specifically and quantitatively to CJC-1295's half life profile is more inference than established fact. For a fuller rundown of adverse effect reports and what's actually documented versus assumed, see cjc 1295 side effects.
Is CJC-1295 FDA approved, and does that affect what we know about its half life?
No. CJC-1295 is not an FDA-approved drug. FDA's guidance on compounding risk for office-use and bulk substances explains the agency's general framework for evaluating whether a bulk drug substance can be used in compounding, and peptides like CJC-1295 that haven't gone through that nomination and review process fall outside it [3]. This matters for the half life question specifically because it means there's no FDA-reviewed pharmacokinetic dataset, no approved label with a stated half life, and no post-market surveillance requirement the way there would be for an approved drug. The 5.8 to 8.1 day figure comes from one industry-sponsored study published in a peer-reviewed endocrinology journal [1], which is real, legitimate science, but it is a single study, run on a small number of subjects, published in 2006. Nobody has published a large modern replication.
How does CJC-1295's half life compare to other GH-related peptides?
| CJC-1295 with DAC | ~5.8 to 8.1 days | Teichman et al., 2006 [1] | |
|---|---|---|---|
| CJC-1295 no-DAC (Mod GRF 1-29) | ~30 minutes (commonly cited) | Not from a major peer-reviewed PK study | |
| Sermorelin (GRF 1-29, unmodified) | A few minutes | Widely cited as very short due to rapid enzymatic degradation | |
| Tesamorelin | ~26 to 38 minutes | FDA-approved label pharmacokinetic data [4] | |
| Native GH (recombinant, subcutaneous) | ~2 to 4 hours | Reflects endogenous-like clearance | Tesamorelin is worth noting because it is FDA-approved (for HIV-associated lipodystrophy), so its half life comes from an actual approved drug label rather than a single independent study, which is a meaningfully different evidence standard than anything available for CJC-1295 [4]. |
Context helps here, because "long half life" only means something relative to alternatives. | Compound | Approx. half life | Source |
What does this mean for dosing frequency in practice?
If you're looking at secondary-source protocols (again, none of this is an approved medical dosing schedule), the half life difference is the entire logic behind frequency choices people describe. DAC-linked CJC-1295 protocols in the literature people cite tend to run once or twice weekly, on the theory that the long half life keeps blood levels elevated between doses without needing daily injections. No-DAC protocols run daily, sometimes twice daily, timed around sleep or training, on the theory that you want a short, sharp GH pulse that mimics natural release rather than a flat elevated baseline. Those are two very different philosophies of how to use a GHRH analogue, and the half life data is really the only hard number backing either one. Everything past that (specific mcg amounts, cycle lengths, how ipamorelin timing should shift around it) is protocol design, not established pharmacology. The cjc 1295 dosage page and the cjc-1295 dac dosage calculator go through that layer in more detail.
Where can you find CJC-1295 that's actually reviewed by a provider?
Because CJC-1295 isn't FDA-approved, sourcing quality varies enormously, and half life data becomes almost irrelevant if the product itself is mislabeled or underdosed, which independent testing has found happens with some research-labeled peptides. If you're going to look into this further, look at cjc 1295 for sale for how CJC-1295 Co reviews providers and points to a provider-reviewed route with a named fulfilling pharmacy partner, rather than an unregulated research-chemical seller. That distinction matters more for CJC-1295 than for most drugs, given the regulatory gray zone it sits in.
Frequently asked questions
What is the half life of CJC-1295 with DAC?
About 5.8 to 8.1 days, based on the original human pharmacokinetic study by Teichman et al. (2006), which reported a mean terminal half life around 6.8 days depending on dose group. That long half life is the entire reason the DAC tag was added to the peptide.
What is the half life of CJC-1295 without DAC?
Around 30 minutes is the figure most commonly cited, though it comes mainly from manufacturer and secondary literature rather than a major peer-reviewed pharmacokinetic study. Without the DAC's albumin-binding tag, the peptide clears from circulation almost as fast as unmodified GHRH fragments do.
Why does DAC extend CJC-1295's half life so much?
DAC (Drug Affinity Complex) covalently binds to albumin, the most abundant protein in blood plasma, once injected. Because albumin isn't cleared or broken down quickly, the peptide effectively hitches a ride and avoids rapid enzymatic degradation, stretching its half life from minutes to days.
How long does CJC-1295 stay in your system after the last dose?
For DAC-linked CJC-1295, using the rule of thumb that a drug takes about 4 to 5 half lives to mostly clear, total time in the system could run 27 to 40 days after a half life around 6.8 days. The no-DAC version clears within hours given its roughly 30-minute half life.
Does CJC-1295's half life determine how often you inject it?
Largely yes, in the protocols described in secondary sources. The long half life of the DAC version supports once or twice weekly injections in theory, while the short half life of the no-DAC version is why daily or multiple daily injections are typically described for it instead.
Is CJC-1295 FDA approved?
No. CJC-1295 is not FDA-approved and hasn't gone through the agency's review process for bulk drug substances used in compounding. There is no FDA-reviewed label, and the half life figures available come from a single independent industry-sponsored study, not an approved drug monograph.
Why is CJC-1295 combined with ipamorelin?
CJC-1295 is a GHRH analogue and ipamorelin is a ghrelin mimetic; they act on different pituitary receptors that both push toward GH release. Earlier research on related GHRH/GHRP combinations shows a larger GH pulse from stacking the two mechanisms, though a large controlled trial of this exact pairing for a specific outcome doesn't exist.
Does a long half life make CJC-1295 with DAC more risky?
Not automatically, but it does mean less ability to stop an effect quickly if something goes wrong, since the compound keeps acting for weeks. Long-term human safety data on sustained, non-pulsatile GH/IGF-1 elevation specific to CJC-1295 in real-world use is limited.
How does CJC-1295's half life compare to tesamorelin?
Tesamorelin, an FDA-approved GHRH analogue, has a reported half life of roughly 26 to 38 minutes per its approved label pharmacokinetic data, much shorter than CJC-1295 with DAC's 5.8 to 8.1 days but similar in range to CJC-1295 without DAC.
Can you inject no-DAC CJC-1295 only once a week?
That wouldn't match its pharmacology. With a half life around 30 minutes, it clears the body within hours, so a once-weekly injection would produce one short GH pulse and then nothing for six days. Protocols built around this version are generally daily, not weekly.
What did the original CJC-1295 study actually measure?
Teichman et al. (2006), published in the Journal of Clinical Endocrinology & Metabolism, measured GH and IGF-1 response and pharmacokinetics after single and multiple doses of CJC-1295 (DAC) in healthy adults, reporting sustained GH and IGF-1 elevation and a multi-day terminal half life.
Where should I look for provider-reviewed CJC-1295?
Given the regulatory gray zone CJC-1295 sits in, sourcing from an unreviewed research-chemical seller adds real risk on top of the pharmacology already discussed. CJC-1295 Co's sourcing guide reviews providers and points toward a provider-reviewed route with a named fulfilling pharmacy partner.
Sources
- Journal of Clinical Endocrinology & Metabolism, Teichman et al. 2006: CJC-1295 with DAC has a terminal half life of approximately 5.8 to 8.1 days and sustains elevated GH and IGF-1 levels with repeated dosing
- Journal of Clinical Endocrinology & Metabolism, Bowers et al., growth hormone releasing peptide/GHRH synergy study: GHRH analogues and ghrelin mimetics (growth hormone releasing peptides) act on distinct receptors that can produce a larger combined GH pulse than either alone
- U.S. Food and Drug Administration, Guidance for Industry: Evaluation of Bulk Drug Substances Nominated for Use in Compounding Under Section 503B: FDA's framework for evaluating bulk drug substances nominated for compounding, which CJC-1295 has not been reviewed and approved under
- U.S. Food and Drug Administration, Egrifta (tesamorelin for injection) prescribing information, NDA 022505: Tesamorelin, an FDA-approved GHRH analogue, has a reported elimination half life of roughly 26 to 38 minutes
- National Center for Biotechnology Information, StatPearls: Growth Hormone Releasing Hormone physiology: Growth hormone is normally released from the pituitary in pulses, predominantly during sleep, rather than as a sustained continuous signal
- U.S. National Library of Medicine, ClinicalTrials.gov record for tesamorelin pharmacokinetics in HIV-associated lipodystrophy: Tesamorelin's clinical development program included pharmacokinetic assessment as part of its path to FDA approval