Peptide Cycling Strategies and the Evidence Behind Them

Why People Cycle Peptides

Users on peptide forums often describe the same pattern with growth hormone (GH) secretagogues: a clear effect in the first few weeks, then less of it. The usual explanation is receptor desensitization, and the community answer is to cycle: run a compound for a set number of weeks, stop, and start again.

The mechanism is real at the cell level. GHRPs such as GHRP-2, GHRP-6 and ipamorelin act on the growth hormone secretagogue receptor (GHSR-1a), the receptor ghrelin uses. In a 2004 cell study, ghrelin-bound GHSR-1a desensitized rapidly and was pulled inside the cell within 20-60 minutes, then took about 6 hours to return to the surface. That fits the observation that a second dose given soon after the first produces a smaller pulse. It doesn't tell us what happens over weeks of daily use in people.

What Human Studies Show About Tolerance

Only a few human studies have tracked GH responses over months. None used ipamorelin or Mod GRF 1-29, the two peptides users most often cycle.

• Hexarelin, a GHRP. In a 1998 study, 12 healthy older adults injected 1.5 mcg/kg subcutaneously twice a day for 16 weeks. The GH response to a test dose fell by about 30% after one week and about 45% by week 16. Four weeks after stopping, it was back to baseline. IGF-1, which carries much of GH's effect on tissue, didn't change significantly at any point.
• MK-677 (ibutamoren), an oral GHSR agonist. In a two-year randomized trial in 65 adults aged 60-81, 25 mg a day raised GH and IGF-1 into the young-adult range over the first year, and second-year analyses showed the same pattern. Fat-free mass rose about 1.1 kg (it fell slightly on placebo), with no change in strength. Fasting glucose rose and insulin sensitivity fell.

Together, these studies suggest tolerance to GHSR agonists in people is partial and reversible, and doesn't necessarily show up in IGF-1. The hexarelin study is the closest thing to evidence for a 4-week break, but it's one small study of a different peptide in older adults. The claim that 8-12 weeks on and 4 weeks off is needed for "full receptor resensitization" is a community convention that no study has tested.

Common Protocols Users Describe

The schedules below come from community guides and vendor guidance, not trials. They're here for comparison with the research, not as recommendations.

The GHRH + GHRP Stack

The most common combination pairs a GHRH analogue such as Mod GRF 1-29 (often sold as CJC-1295 without DAC) with a GHRP such as ipamorelin or GHRP-2. The two act on different pituitary receptors, so together they release more GH than either does alone; Cyril Bowers' early human studies showed this synergy with an IV bolus of GHRP-1 plus GHRH.

The protocol users describe most often is 100 mcg of Mod GRF 1-29 with 100-200 mcg of ipamorelin, injected subcutaneously one to three times a day (on waking, after training, or at bedtime), for 8-12 weeks followed by about 4 weeks off. Many simplify this to one bedtime dose, and some run 5 days on and 2 days off each week instead of taking a long break.

Ipamorelin is the usual GHRP choice because, in Novo Nordisk's 1998 animal studies, it released GH in pigs without raising ACTH or cortisol, even at more than 200 times the dose needed for GH release. Human data are limited: the largest trial, a 2014 Phase 2 study in 117 patients after bowel surgery, missed its main outcome and didn't measure body composition. As of October 2026, ipamorelin isn't approved anywhere.

The Healing-Focused Protocol

BPC-157 and TB-500 come up in cycling discussions, but neither acts on GHSR, and there's no evidence of the tolerance described above. Rodent studies link BPC-157 to new blood vessel growth; TB-500 is a short fragment of thymosin beta-4, an actin-binding protein involved in cell migration. A 2025 systematic review of BPC-157 in sports medicine found 35 preclinical studies and one small clinical report, with no clinical safety data. The TB-500 fragment has no human data at all.

Users cycle these for a practical reason: they run them for a specific injury and then stop. They commonly report 250-500 mcg of BPC-157 a day by subcutaneous injection, sometimes split into two doses and often near the injury. Vendor guidance for TB-500 describes 2-2.5 mg twice a week for 4-6 weeks, then lower maintenance doses; forum reports go up to 2-5 mg twice weekly. Runs of 4-8 weeks are typical, and no human study has tested any of these doses or durations.

Integrating Peptides with Anabolic Cycles

No controlled study has tested a GH secretagogue combined with anabolic steroids, so this section describes community practice and its reasoning. Our overview of peptides versus traditional anabolics explains how the two classes differ in mechanism.

During a Steroid Cycle

Lifters add a GHRH + GHRP stack during a steroid cycle hoping for more lean tissue and less fat gain while bulking. The closest human data are modest: in the MK-677 trial, older adults gained about 1.1 kg of fat-free mass over a year versus placebo, without getting stronger. Whether a secretagogue adds anything measurable on top of supraphysiologic testosterone is unknown. Our comparison of peptide and steroid results for muscle and strength covers realistic expectations.

Some users take GHRP-6 after training while bulking precisely because of the strong hunger they report soon after injection, which fits its action as a ghrelin mimetic.

During the Cruise or Bridge

A cruise is the period between steroid cycles when users drop to a testosterone dose near the replacement (TRT) range. Users often describe a lighter secretagogue run here, such as 100 mcg each of Mod GRF 1-29 and ipamorelin twice a day, to hold on to muscle. That's plausible given what GH does, but nobody has measured it in this setting.

During Post-Cycle Therapy (PCT)

PCT is the period after a steroid cycle when users try to restart their own testosterone production (the HPTA, or hypothalamic-pituitary-testicular axis). Community guides often say ipamorelin is the only GHRP to use here, because GHRP-2 and GHRP-6 raise prolactin and cortisol, and persistently high prolactin suppresses testosterone.

Part of that holds up. In a 1997 study of six healthy young adults, IV GHRP-2 raised prolactin and cortisol along with GH, with a cortisol response similar to that from corticotropin-releasing hormone. Those were short rises after single doses, though, and no study has tested whether repeated GHRP-2 or GHRP-6 use slows HPTA recovery. Ipamorelin's lack of effect on cortisol comes from the pig studies; we found no human study confirming it. Users who add a peptide during PCT most often describe ipamorelin alone at 200-300 mcg before bed, or a low-dose stack with Mod GRF 1-29.

Peptide Cycling Strategies at a Glance

The schedules in this table are community conventions. None has been tested in a trial.

The CJC-1295 with DAC Question

Forum guides often warn that CJC-1295 with DAC causes a constant "bleed" of GH that quickly downregulates receptors and shuts down natural production. The human data don't match that description. In a 2006 study, healthy men aged 20-40 got one injection of 60 or 90 mcg/kg, with GH sampled every 20 minutes overnight before and one week after the dose. The frequency and size of GH pulses didn't change. Trough GH between pulses rose about 7.5-fold, and mean GH and IGF-1 each rose about 45%. A companion study found GH stayed 2-10 times above baseline for 6 days or more after one dose (half-life about 6-8 days), and IGF-1 stayed raised for up to 28 days after repeated doses.

So CJC-1295 with DAC raises the baseline between pulses rather than flattening them. That differs from the body's own rhythm and is a fair reason for caution, but these studies didn't show blunted pulses or suppression. They also lasted weeks, not months; as of October 2026, there are no published human data on long-term use. Our CJC-1295 profile covers its trial side effects and why most users actually mean the no-DAC form.

WADA Status

As of October 2026, WADA's 2026 Prohibited List bans every peptide on this page at all times for tested athletes. CJC-1295, ipamorelin, GHRP-2, GHRP-6, hexarelin and MK-677 fall under S2.2.4 (growth hormone releasing factors). TB-500 is listed under S2.3 as a thymosin beta-4 derivative, and BPC-157 is named under S0 (non-approved substances).

What We Still Don't Know

• Whether ipamorelin or Mod GRF 1-29 lose effect over weeks of use in people, and how long a break restores the response. No study has measured either.
• Whether a smaller GH pulse matters if IGF-1 stays up, as it did with hexarelin and MK-677.
• Whether secretagogues add lean mass on top of anabolic steroids, or change how quickly testosterone production recovers afterward.
• What months of CJC-1295 with DAC do to the GH axis.

The health questions raised by years of combined use are covered in our article on long-term effects of peptide use compared with anabolics.