Evidence Levels
Not all peptide research is created equal. Peptidings applies a consistent evidence hierarchy to every compound in the library—so you always know whether you’re reading about an FDA-approved drug or a compound that has never been tested in a human being.
75 compounds classified across 5 tiers
How the Evidence Hierarchy Works
The peptide research landscape spans an enormous range of evidence quality. Semaglutide has been studied in tens of thousands of patients across multiple Phase III trials and is approved by the FDA for two separate indications. Other compounds in the same conversations have never been tested in a single human subject. Treating these as equivalent—or leaving readers to infer the difference from vague language—is exactly the kind of intellectual dishonesty Peptidings exists to counter.
Every compound in the Peptidings library is assigned to one of four ranked tiers or one lateral category. The ranked tiers reflect the strongest available human evidence for that compound. The lateral category—“It’s Complicated”—exists for the handful of compounds where a single tier would actively mislead, because the evidence picture differs meaningfully depending on the specific question being asked.
Tier assignments are based on the primary research literature, not on community consensus, supplier claims, or the enthusiasm a compound generates in biohacking forums. They are reviewed annually and updated when significant new research is published. The tier for each compound is displayed in the Quick Facts table at the top of every pillar article.
One important clarification
Evidence tier reflects the strongest available data for a compound—not evidence for every application. An approved drug is approved for specific indications. A compound with Phase II clinical trial data has that data for the specific endpoints studied. Neither assignment validates the broader range of uses discussed in self-experimentation communities. The pillar article for each compound specifies exactly what the evidence does and does not show.
Approved Drug
19 compoundsThe compound has completed the full clinical development pathway and holds regulatory approval.
A compound reaches this tier when it has received regulatory approval in one or more countries for at least one indication. Approval means the compound has completed the full clinical development pathway—Phase I safety, Phase II dose-finding, Phase III efficacy—and a regulatory body has determined that the benefit–risk profile is acceptable for a defined patient population.
Two important caveats. First, approval is indication-specific: a compound approved for one condition is not automatically validated for the unrelated applications often discussed in self-experimentation communities. Second, approved status in one country does not mean approved everywhere. Thymosin Alpha-1, for instance, is approved in more than 35 countries but not in the United States. Regulatory status is documented for each compound in its Quick Facts table.
How we assign this tier
Confirmed regulatory approval by FDA, EMA, or an equivalent national agency for at least one indication, verified against primary regulatory sources.
Bone & Joint Health
Cardiovascular
Bone & Joint Health
Cardiovascular
Cardiovascular
Sexual Health & Hormonal
Cancer & Oncology
Weight Loss & Metabolic
Cardiovascular
Cancer & Oncology
Sexual Health & Hormonal
Bone & Joint Health
Gut Health
Weight Loss & Metabolic
Bone & Joint Health
Growth Hormone
Immune Health
Weight Loss & Metabolic
Cancer & Oncology
Clinical Trials (Phase I+)
21 compoundsHuman clinical trial data exists in the peer-reviewed record—but regulatory approval has not been granted.
Compounds at this tier have published human clinical trial data—Phase I, II, or III—in the peer-reviewed record. This is meaningful evidence. Human bodies have been studied, outcomes have been measured, and the methodology has survived peer review. These compounds have cleared the significant bar of demonstrating sufficient safety and preliminary efficacy to progress through human testing.
This tier covers a wide range of evidence strength. A single Phase I safety study in 12 healthy volunteers and a completed Phase III efficacy trial in 3,000 patients both qualify. The difference matters, and Peptidings articles describe the specific trial data rather than treating the tier as monolithic. A compound with one small Phase I study is not the same as one with multiple Phase II trials, even though both appear in this tier.
How we assign this tier
At least one published Phase I, II, or III trial with human subjects, indexed in PubMed or a major clinical trial registry, with results available in the peer-reviewed literature.
Weight Loss & Metabolic
Gut Health
Brain & Cognitive
Growth Hormone
Gut Health
Growth Hormone
Growth Hormone
Growth Hormone
Sexual Health & Hormonal
Gut Health / Immune Health
Antimicrobial / Immune Health
Tanning & Melanocortin
Tanning & Melanocortin
Growth Hormone
Weight Loss & Metabolic
Sexual Health & Hormonal
Sexual Health & Hormonal
Weight Loss & Metabolic
Growth Hormone
Weight Loss & Metabolic
Immune Health / Gut Health
Pilot / Limited Human Data
12 compoundsHumans have been studied, but the data falls short of conventional clinical trial standards.
Some compounds have been administered to humans in a research context—but the data falls short of what most researchers would call a conventional clinical trial. This tier covers small observational studies, pilot investigations with limited sample sizes, compassionate-use reports, and early feasibility studies that generated human data without meeting the design standards of a full Phase I trial.
Pilot data is real evidence. It is not animal data extrapolated to humans. But it is also insufficient to draw firm conclusions about efficacy or long-term safety. These compounds occupy a genuinely uncertain middle ground, and that uncertainty is reflected in how Peptidings covers them. BPC-157 is the canonical example: three small human studies—knee injection, interstitial cystitis, and an intravenous safety study—without a single conventional Phase I, II, or III trial.
How we assign this tier
Published data involving human subjects that does not qualify as a conventional Phase I trial or higher: pilot studies, feasibility studies, small observational studies, or compassionate-use case series with measurable outcomes.
Weight Loss & Metabolic
Skin & Cosmetic
Injury Recovery & Tissue Repair
Sleep, Stress & Recovery
Anti-Aging & Longevity
Anti-Aging & Longevity
Skin & Cosmetic
Skin & Cosmetic
Brain & Cognitive / Sleep & Stress
Brain & Cognitive
Skin & Cosmetic
Anti-Aging & Longevity / Immune Health
Preclinical Only
21 compoundsNo published human data. Evidence is entirely animal, in vitro, or mechanistic.
No published human data exists for these compounds. The evidence base is entirely animal models, cell culture (in vitro), or mechanistic inference—the compound binds to a receptor known to be relevant, or produces an effect in a rat model, or inhibits an enzyme in a petri dish. That is not nothing. Preclinical research is a necessary step in the development of any drug, and interesting animal results are worth knowing about. But the translation from animal models to human outcomes is notoriously unreliable, and mechanistic plausibility is not clinical evidence.
Many of the compounds that generate the most enthusiasm in self-experimentation communities sit in this tier. The enthusiasm is understandable; the evidence doesn’t yet support it. Peptidings covers these compounds honestly: the preclinical findings are worth describing, but the human evidence gap is not minimized or explained away.
How we assign this tier
No published studies involving human subjects in any context. Evidence is limited to animal in vivo studies, in vitro cell culture, computational modeling, or mechanistic extrapolation from related compounds.
Weight Loss & Metabolic
Tanning & Melanocortin
Antimicrobial
Sleep, Stress & Recovery
Antimicrobial
Brain & Cognitive
Performance & Body Composition
Anti-Aging & Longevity
Performance & Body Composition
Performance & Body Composition
Injury Recovery & Tissue Repair
Antimicrobial
Performance & Body Composition
Anti-Aging & Longevity
Antimicrobial
Sleep, Stress & Recovery
Brain & Cognitive
Performance & Body Composition
Brain & Cognitive
Anti-Aging & Longevity
Skin & Cosmetic
It’s Complicated
2 compoundsThe evidence tier depends on which specific question you’re asking.
Some compounds resist a single-tier assignment because the evidence tier depends entirely on which specific question you are asking about them. Forcing these compounds into one of the four ranked tiers would require either overstating the evidence for some applications or understating it for others—exactly the kind of oversimplification this site exists to counter.
The “It’s Complicated” category is a lateral designation, not a fifth rung. It means: the evidence picture is genuinely more nuanced than a single badge can represent, and the article explains why. Each compound in this category receives a specific explanation of what the complication is. This is not a hedge—it is an accurate description of the evidence landscape.
How we assign this tier
The compound has meaningfully different evidence profiles depending on the route of administration, the specific fragment or variant being discussed, or the indication being evaluated—and those differences are large enough that a single tier would actively mislead a reader trying to evaluate the compound for a specific purpose.
Skin & Cosmetic / Injury Recovery
Decades of human use data in topical cosmetic applications. Injectable systemic use—common in self-experimentation communities—has far less human evidence. A copper peptide applied to skin and one injected subcutaneously are not the same risk–benefit proposition.
Injury Recovery & Tissue Repair
The parent molecule Thymosin β4 (Tβ4) has Phase I safety data and Phase II/III ophthalmic trial data. TB-500, the 7-amino-acid fragment most commonly discussed in self-experimentation contexts, has zero published human trials. The two molecules share an actin-binding motif but differ in size by a factor of six. The evidence base for Tβ4 does not automatically transfer to TB-500.
Tier assignments are reviewed annually and updated when significant new research is published. If you find a tier assignment that you believe is inaccurate—with a primary source to support the correction—use the contact page.