CJC-1295 with vs without DAC: the half-life difference that changes everything

Two molecules, one name

Growth-hormone-releasing hormone (GHRH) tells the pituitary to release growth hormone, and its first 29 amino acids, GHRH(1-29), carry its activity. That fragment, as sermorelin, was once an approved drug for children with growth hormone deficiency. Its weakness is that it is broken down quickly in the blood, which limits how long it acts ¹. In the early 2000s, the Canadian company ConjuChem set out to fix that, and CJC-1295 was the result.

Today two different products are sold under that name. One is the molecule ConjuChem made and tested in people. The other, sold as 'CJC-1295 without DAC', 'CJC-1295 no DAC' or Mod GRF 1-29, is a related peptide that was never part of those trials. Our encyclopedia keeps them as separate entries, CJC-1295 and Mod GRF 1-29, because they are different molecules with different evidence.

Side by side

From our encyclopedia entries and the studies cited below, as of October 3, 2026:

The chemistry: what DAC means

ConjuChem's chemists started from GHRH(1-29) and made four amino acid substitutions that protect it from dipeptidyl peptidase-IV and other enzymes that normally chop it up. That tetrasubstituted peptide is what is now sold as Mod GRF 1-29. They then added a reactive maleimide group to a lysine at the end of the chain, the part the company called a Drug Affinity Complex, or DAC ².

The maleimide group bonds to a free thiol on cysteine-34 of albumin, the most abundant protein in blood, so after injection the peptide rides on albumin, which lasts weeks in circulation. In the 2005 study that introduced it, the albumin conjugates resisted dipeptidyl peptidase-IV and remained active on pituitary cells; in rats, the best compound, CJC-1295, produced four times the growth hormone of unmodified GHRH(1-29) over two hours and was still present in plasma after 72 hours, bound to albumin from 15 minutes onwards ². That albumin bond is the whole difference between the two products.

The 2006 human trials

CJC-1295 with DAC was tested in two randomised, placebo-controlled, double-blind ascending-dose trials in healthy adults aged 21 to 61, lasting 28 and 49 days. After a single injection under the skin, mean growth hormone rose two- to tenfold for six days or more, and mean IGF-1 rose 1.5- to threefold for 9 to 11 days. The estimated half-life was 5.8 to 8.1 days. With repeated doses, IGF-1 stayed above baseline for up to 28 days, and no serious adverse reactions were reported in the trials ¹.

A second 2006 study asked whether that sustained exposure flattened the natural rhythm of growth hormone, which is released in pulses. Healthy men had blood drawn every 20 minutes overnight before and one week after an injection. The frequency and size of growth hormone pulses did not change, but trough levels between pulses rose 7.5-fold, mean growth hormone by 46% and IGF-1 by 45% ³. A 2009 proteomics analysis of serum from 11 young men before and after an injection identified protein changes linked to growth hormone action, as markers of exposure ⁴.

Mod GRF 1-29: the unstudied twin

Mod GRF 1-29 is the tetrasubstituted peptide without the DAC group, so it should resist enzymes better than sermorelin while lacking any means of binding albumin. Users treat it as a short-acting alternative that produces brief growth hormone bursts, often paired with ipamorelin. The problem is that none of this has been measured in people. Our entry records that no pharmacokinetic study of Mod GRF 1-29 appears in PubMed; the 'about 30 minutes' half-life repeated online has no published source ⁵. Every human number for CJC-1295, the week-long half-life, the IGF-1 rise, the preserved pulses, belongs to the version with DAC.

The naming chaos, documented

The confusion is not just online. In 2009, Norwegian police and customs submitted an unknown preparation for analysis; mass spectrometry found a 29-amino-acid peptide with a C-terminal amide, whose sequence the chemists described as consistent with a peptide then marketed as CJC-1295 ⁶. In other words, a product sold as CJC-1295 contained the 29-amino-acid peptide, the version without DAC. The consequence for buyers is that a vial labelled CJC-1295 may contain either molecule, and the human trial data apply only to one.

That matters for exposure. A peptide that lasts a week accumulates if taken as often as a short-acting one, and a peptide that lasts minutes does nothing between doses. A buyer who does not know which molecule is in the vial cannot know which pattern of exposure they are getting.

Why the pulse pattern matters

Growth hormone is normally released in bursts, mostly at night, with low levels in between. Researchers consider that pulsatile pattern important for many of the hormone's effects, which is why the 2006 pulsatility study was designed: a drug that kept growth hormone high all the time would be a different intervention from one that amplified the natural bursts ³. CJC-1295 with DAC did something in between. The pulses kept their timing and size, but the troughs between them rose 7.5-fold, so total exposure to growth hormone went up substantially and stayed up for days ³.

That is the trade-off behind the online debate. Users who prefer Mod GRF 1-29 argue that a short-acting peptide creates a brief burst that mimics a natural pulse and then clears. That may be true, but it is an argument from physiology, not data: no study has measured what Mod GRF 1-29 does to growth hormone pulses in people ⁵.

How to tell which one is in a vial

The two molecules differ in mass, which is how a laboratory can tell them apart. Our encyclopedia records a molecular weight of 3,647.24 for CJC-1295 with DAC and 3,367.92 for Mod GRF 1-29, a difference of about 279 daltons from the albumin-binding group ⁵. A genuine certificate of analysis should name the molecule unambiguously, state which version it is, and report a measured mass that matches one figure or the other. A certificate that says only 'CJC-1295', or reports a mass that matches neither, does not tell you what you have. Our COA Decoder explains how mass checks work, and our guide to spotting a fake certificate shows a worked example.

The ipamorelin pairing

The short-acting version is most often sold blended with ipamorelin, a ghrelin-receptor agonist, at equal amounts in one vial. The idea is that a GHRH analogue and a ghrelin mimetic act on the pituitary through different routes and amplify each other. No study has tested that pair in people, blended or separately, and neither component is approved ⁵. Our blends hub sets out what the CJC-1295 and ipamorelin mix contains, and our article on the stack covers how it is used.

What the animal work added

In mice lacking the GHRH gene, CJC-1295 given daily from one week of age for five weeks produced normal body weight and length; dosing every 48 hours normalised bone length, and every 72 hours improved growth without normalising it ⁷. Because CJC-1295 bonds to plasma proteins, it is hard to detect directly; anti-doping researchers developed a method to capture and confirm it in horse plasma at very low concentrations ⁸, a sign of where the compound has turned up.

Where the approved GHRH drugs fit

CJC-1295 is one of several attempts to make GHRH last longer. Two reached approval. Sermorelin, the unmodified GHRH(1-29), was approved in the US as Geref for children with growth hormone deficiency and later discontinued; tesamorelin, a GHRH analogue with a chemical group added to the start of the chain, is approved as EGRIFTA to reduce excess abdominal fat in adults with HIV ⁵. Both went through the trials, manufacturing standards and regulatory review that CJC-1295 never completed. Our comparison of somatropin and sermorelin explains how a releasing hormone differs from growth hormone itself.

Who uses it, and why

A study of 23 discussion threads on nine bodybuilding forums found women using CJC-1295 for weight loss, muscle, younger-looking skin, sleep and injury healing, usually alongside other performance and image drugs, and worrying about how sex differences in growth hormone might change its effects ⁹. None of those uses has been tested. The only human studies are the healthy-volunteer trials above, which measured hormone levels, not body composition, sleep or healing.

Safety and status

Neither version is approved by FDA. CJC-1295's US compounding nomination was withdrawn, and FDA records serious adverse events associated with it, including increased heart rate and a systemic vasodilatory reaction ⁵. Long-term effects of raising growth hormone and IGF-1 for weeks at a time, including on blood sugar and cell growth, have not been studied. Both versions are prohibited at all times by WADA under S2.2.4, growth hormone releasing factors ⁵.

The bottom line

As of October 3, 2026, 'CJC-1295 with DAC' is a long-acting GHRH analogue with two small 2006 trials in healthy adults and a week-long half-life. 'CJC-1295 without DAC' is Mod GRF 1-29, a related short-acting peptide with no human data at all. They are not interchangeable, the name on a vial does not reliably tell you which you have, and neither is approved. If you see a claim about 'CJC-1295', the first question to ask is which of the two it is about. Our comparison of tesamorelin and CJC-1295 shows what a GHRH analogue that did complete approval looks like.

Frequently asked questions

What is the difference between CJC-1295 with and without DAC?

CJC-1295 with DAC has a chemical group that bonds to albumin, giving a half-life of 5.8 to 8.1 days in people. Without DAC, the peptide (Mod GRF 1-29) cannot bind albumin and its human half-life has never been measured.

Is Mod GRF 1-29 the same as CJC-1295?

It is CJC-1295's peptide chain without the albumin-binding DAC group. Sellers often call it CJC-1295 without DAC, but the human trials of CJC-1295 used the version with DAC.

What is the half-life of CJC-1295 without DAC?

No published study has measured it in people. The 'about 30 minutes' figure online has no published source.

Is CJC-1295 approved or legal?

Neither version is FDA-approved, its compounding nomination was withdrawn, and both are prohibited by WADA.

Related on Grey Peptides

• CJC-1295
• Mod GRF 1-29
• Tesamorelin vs CJC-1295

Sources

1. Teichman, S. L., et al. (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. J Clin Endocrinol Metab, 91(3), 799-805. PMID: 16352683
2. Jetté, L., et al. (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 analog. Endocrinology, 146(7), 3052-8. PMID: 15817669
3. Ionescu, M., et al. (2006). Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. J Clin Endocrinol Metab, 91(12), 4792-7. PMID: 17018654
4. Sackmann-Sala, L., et al. (2009). Activation of the GH/IGF-1 axis by CJC-1295, a long-acting GHRH analog, results in serum protein profile changes in normal adult subjects. Growth Horm IGF Res, 19(6), 471-7. PMID: 19386527
5. Grey Peptides encyclopedia entries for CJC-1295 (status, FDA adverse event note, WADA S2.2.4) and Mod GRF 1-29 (no pharmacokinetic study in PubMed). Read October 3, 2026.
6. Henninge, J., et al. (2010). Identification of CJC-1295, a growth-hormone-releasing peptide, in an unknown pharmaceutical preparation. Drug Test Anal, 2(11-12), 647-50. PMID: 21204297
7. Alba, M., et al. (2006). Once-daily administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH knockout mouse. Am J Physiol Endocrinol Metab, 291(6), E1290-4. PMID: 16822960
8. Timms, M., et al. (2019). A method for confirming CJC-1295 abuse in equine plasma samples by LC-MS/MS. Drug Test Anal, 11(8), 1248-1257. PMID: 30938069
9. Van Hout, M. C., et al. (2016). Netnography of Female Use of the Synthetic Growth Hormone CJC-1295: Pulses and Potions. Subst Use Misuse, 51(1), 73-84. PMID: 26771670

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.