Our evidence-tier framework

Why we tier evidence

Peptides span a huge range of evidence quality — from compounds with multiple human randomized controlled trials to ones supported only by mouse data and marketing. Lumping them together as "peptides work" or "peptides are unproven" is misleading in both directions. So every claim on this site is tagged with an evidence tier, from 1 (strongest) to 5 (weakest), so you can calibrate confidence at a glance.

The tiers describe how strong the evidence is, not whether something is good or bad. A Tier 4 compound isn't necessarily useless — it means the human data isn't there yet, and you should treat it as experimental.

The five tiers

The tier reflects the best available evidence for a specific claim — the same peptide can be Tier 2 for one indication and Tier 4 for another.

• Tier 1 — Strong human evidence. Multiple high-quality randomized controlled trials (RCTs) and/or meta-analyses in humans, with consistent results. This is the standard regulated medicines are held to.
• Tier 2 — Solid human evidence. At least one well-conducted human RCT, strong consistent clinical data, or an established, non-controversial methodology. Approved-abroad indications often sit here.
• Tier 3 — Emerging human + replicated animal. Human pilot studies or observational data plus replicated animal evidence. Promising and grounded, but not yet confirmed by large human trials.
• Tier 4 — Mechanism and animal data. A plausible biological mechanism plus animal studies, with little or no human outcome data. Genuinely experimental; you'd be self-experimenting at the frontier.
• Tier 5 — Hypothesis, anecdote, or marketing. Theoretical rationale, individual anecdotes, community signal, or promotional claims with no rigorous support. Interesting to track, not a basis for decisions.

How we apply it

We assign the tier to the specific claim, not the compound in general, because the same peptide often has very different evidence for different uses. BPC-157, for example, has replicated animal data for gut repair (Tier 3) but only mechanistic support for some of the systemic claims made about it (Tier 4). Community discussion — like our Reddit-signal analyses — is always Tier 5: useful for spotting what people care about, never proof that something works.

When evidence is mixed, we tier to the best-quality body of evidence for that claim and explain the uncertainty in the text rather than hiding it behind a single number.

What the tiers are not

The tier is not a recommendation, a safety rating, or a substitute for medical advice. A high tier means the evidence is strong, not that a compound is right for you; a low tier means the evidence is thin, not that something is definitely ineffective or unsafe. Safety, legality, and personal suitability are separate questions covered elsewhere on the site.

A note on honesty

The point of the framework is to let us cover the full peptide landscape — including popular, low-evidence compounds people are clearly going to research anyway — without either hyping them or dismissing them. Tagging the evidence honestly is how we stay useful and trustworthy at the same time. Our medical reviewer signs off on tier assignments as part of the review process.