Peptide Cycling and Drug Testing: What Athletes Should Know

Two meanings of cycling

In most peptide communities, cycling means alternating periods on and off a compound, usually because users believe the effect fades with steady use. For an athlete in a sport that follows the World Anti-Doping Code, the word often picks up a second meaning: timing use so nothing shows up on test day. That second meaning rests on a misunderstanding of how anti-doping rules work.

The short version: as of October 2026, every peptide discussed here is on WADA's Prohibited List in a class that is banned at all times, in and out of competition. A cycle that ends weeks before an event doesn't make the earlier use permitted. At most it changes the odds of one kind of evidence, and anti-doping organizations rely on several. For the wider regulatory picture, see our overview of regulatory changes affecting peptide use in sport.

Where the common peptides sit on the 2026 list

WADA's 2026 Prohibited List has been in force since January 1, 2026. These placements come from the list itself:

An earlier version of this page listed TB-500 under S0 alongside BPC-157. That was wrong. TB-500 sits in S2, and the difference affects sanctions: all S0 substances are Specified Substances, while all S2 substances are non-Specified. In its case announcements, USADA gives the default ban as two years for use of a specified substance and four years for use or possession of a non-specified one.

The 2027 list takes effect on January 1, 2027. USADA's athlete advisory describes its changes as relatively minor, with one that matters here: the S0 class now names "peptides" in general, so a peptide with no human approval anywhere is likely banned even if the list doesn't name it.

What detection research shows

Anti-doping labs look for prohibited peptides in two broad ways. They can find the compound or its breakdown products directly, or they can spot the hormonal changes it causes.

Direct detection

Published mass spectrometry methods exist for each peptide in the table, but human excretion data are thin.

• GH-releasing peptides. In a 2015 study from the Moscow anti-doping lab, one volunteer per compound took a nasal dose. GHRP-2 and its metabolites were found in urine for up to 47 hours and GHRP-6 for about 23 hours, and metabolites of hexarelin and ipamorelin were still detectable after the parent drugs had cleared. The authors concluded that the detection window depends on individual metabolism, the drug preparation and the route.
• CJC-1295. The version with a drug affinity complex (DAC) binds to albumin in the blood. In 2006 dose-finding trials in healthy adults, its estimated half-life was 5.8-8.1 days. After one injection, GH stayed raised for 6 days or more and IGF-1 for 9-11 days; after repeated doses, IGF-1 stayed above baseline for up to 28 days. A 2016 Cologne method detected CJC-1295 and other GHRH analogues in plasma below 50 pg/mL.
• BPC-157. The US anti-doping lab in Salt Lake City published a urine method in 2017 after finding BPC-157 in confiscated vials. It detects the peptide down to 0.1 ng/mL, and BPC-157 was stable in urine for at least 4 days. A 2023 method lowered the detection limits and added five metabolites, though those metabolites were identified in lab incubations rather than in people. We found no human excretion study, so nobody can say how long BPC-157 stays detectable after use.
• TB-500. The Ghent doping lab characterized the TB-500 fragment (Ac-LKKTETQ) in 2012 and proposed a way to detect it in plasma and urine. There's no human excretion data here either.

These figures mostly come from single doses in small groups of volunteers, and they don't mean use outside the window is invisible.

The biomarker route

Growth hormone secretagogues raise GH, and GH raises IGF-1 and markers of collagen turnover. WADA's Athlete Biological Passport has an endocrine module that tracks two of these markers in blood: IGF-1 and P-III-NP (the N-terminal propeptide of type III collagen). Labs report both values, a GH-2000 score is calculated from them, and the results are assessed over time for each athlete, the same way the passport already handles blood and steroid markers.

WADA's 2025 laboratory guidelines say the module detects GH doping and "may also have utility in detecting GH secretagogues and IGF-I abuse." The technical document that replaces those guidelines on January 1, 2027 names hGH secretagogues, analogues and releasing factors, along with IGF-1, among the substances it is meant to uncover.

We couldn't find a published study measuring how long IGF-1 and P-III-NP stay above a person's own baseline after a secretagogue is stopped.

The GH "bleed" claim about CJC-1295 with DAC

Forum guides, and earlier copy on this site, often say CJC-1295 with DAC causes a constant "bleed" of growth hormone that replaces the body's natural pulses. The one human study that measured pulses doesn't support that. Ionescu and Frohman (2006) sampled blood every 20 minutes overnight in healthy men aged 20-40, before and one week after a single injection of 60 or 90 mcg/kg. The frequency and size of GH pulses didn't change. The baseline between pulses did: trough GH rose about 7.5-fold, mean GH rose 46% and IGF-1 rose 45%.

So in that study the long-acting form raised the floor under normal pulses instead of flattening them. For testing, the parts that matter are the multi-day half-life and the IGF-1 rise.

Why a timed washout isn't a safe harbor

Several features of the anti-doping system make detection windows a poor guide to risk.

The ban applies year-round. S0 and S2 substances are prohibited out of competition as well as in competition, so an off-season sample is judged by the same list as one collected on meet day.

Use counts without a positive test. In 2024 an arbitrator gave a US speedskater a one-year ban for using a supplement that contained BPC-157, even though five of her tests had come back negative; she had declared the supplement on her doping control forms. In 2025 a triathlete accepted a four-year ban after a whistleblower tip led USADA to evidence that he had possessed and used BPC-157 and TB-500 and had promoted peptides to followers. Neither case started with a positive sample. Our piece on the legal side of peptide use for athletes covers how sport rules differ from FDA enforcement.

Samples are stored. WADA says that under the Code, samples can be stored for up to 10 years after their first analysis and reanalyzed with newer methods, with the same legal weight. A sample that passes with 2026 methods can be tested again with later ones, and the passport can flag a trend even when no single sample contains the drug.

Product contents are uncertain. USADA reminds athletes that they are strictly liable for what's in their bodies. The speedskater's supplement also turned out to be contaminated with DHEA, a second prohibited substance. Gray-market peptide vials carry similar risks; see our guide to contamination and counterfeits.

Medical exemptions are unlikely. USADA says a therapeutic use exemption for BPC-157 is unlikely to be approved because permitted alternatives exist, though it reviews each application.

Why users cycle in the first place

Outside of testing, the usual reason for cycling is the belief that the body stops responding to continuous use. Users commonly describe on/off patterns such as weekdays on and weekends off, or blocks of several weeks followed by a break. We couldn't trace these schedules to any trial; they come from community and vendor guides.

The human evidence on desensitization is limited. In a 1998 study, 12 healthy older adults injected hexarelin under the skin twice daily for 16 weeks. Their GH response, measured as area under the curve, fell from 19.1 to 10.5 by week 16, a drop of about 45%. Four weeks after stopping, a new dose produced a response close to baseline again. The authors called the attenuation "partial and reversible." That's one small study of one GH-releasing peptide in older adults, and we found nothing comparable for ipamorelin or the GHRH analogues.

For a tested athlete, the desensitization question doesn't change the rules. The "on" weeks of any schedule are still use of a prohibited substance. The broader fairness and health questions are covered in our article on the ethics of performance enhancement.

What we still don't know

• How long BPC-157 and TB-500 remain detectable in human urine. We found no published human excretion studies for either.
• How long IGF-1 and P-III-NP stay above an athlete's own baseline after a GH secretagogue is stopped.
• Whether the GH response to ipamorelin or the GHRH analogues fades with long-term use the way hexarelin's partly did.
• How quickly labs will add newer peptides to routine screening. USADA's 2027 advisory describes a "striking upward trend" in peptide use and warns that not every prohibited peptide is listed in its Global DRO lookup database.