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Reading the evidenceLesson 1 of 34 min

The four evidence tiers

How we grade peptide evidence: the four tiers

The dose math, a reminder before each dose and the log of what you took, in one app: Claritide for iPhone.

Four labels, applied consistently

Every compound in the Claritide library carries one of four evidence tiers. They come straight from the Playbook's research context reference, and they are the fastest way to calibrate how much weight to give any claim.

Tier 1: Clinical trials

Retatrutide, tesamorelin, semaglutide, tirzepatide.

Phase 2 and Phase 3 trials with hundreds to thousands of participants, randomised, controlled, published in journals like the New England Journal of Medicine and The Lancet.

Tesamorelin is FDA-approved with Phase 3 data. Retatrutide's Phase 2 enrolled 338 adults over 48 weeks, with Phase 3 TRIUMPH results following. Semaglutide's STEP 1 enrolled 1,961. Tirzepatide's SURMOUNT-1 enrolled 2,539.

What this tier buys you: known effect sizes, known side effect rates with percentages attached, known contraindications, and a dosing schedule derived from actual dose-finding work rather than practice convention.

Tier 2: Small human studies

GHK-Cu topical, DSIP.

GHK-Cu topical has small human studies over 20+ years. Most report benefits on skin, including a biopsy study that found more new collagen; a leg-ulcer trial and a post-laser study found no objective difference. DSIP has three small human trials from the 1980s–90s with 6 to 25 participants, one double-blind showing significant improvement in sleep efficiency and latency.

What this tier buys you: real human data. What it does not buy you: modern trial sizes, long-term safety characterisation, or dose-response curves.

Note that the tier is about study quality, not compound quality. GHK-Cu topical is one of the better-studied peptides available; that still lands it here rather than in tier 1.

Tier 3: Preclinical + practitioner use

BPC-157, MOTS-C.

BPC-157 has dozens of animal studies with consistent results, five small human studies (FDA's July 2026 count), and wide clinical practice use. MOTS-C has strong preclinical data published in Cell Metabolism and Nature Communications, plus a Phase 1 safety trial of a modified analog.

What this tier means in practice: the mechanism is well characterised, the animal data is consistent, and no controlled human trial has demonstrated the effect you are seeking. Dosing comes from practitioner protocols refined over years, not from dose-finding studies.

Tier 4: Practitioner experience only

TB-500 solo, multi-peptide stacking, injectable GHK-Cu.

No controlled human studies. TB-500's parent protein has been studied extensively; the fragment used in practice has not been studied separately in humans. Injectable GHK-Cu has not been studied in human trials at all.

This tier is not "worthless". It is "you are the study".

How to use the tiers

They do not tell you whether to use a compound. They tell you how much confidence the numbers deserve, and therefore how carefully to track your own results.

At tier 1, the trial data is a reasonable prediction of your outcome. At tier 4, your own daily log is the only evidence that will ever exist about whether it worked for you.

That is the actual reason Claritide makes tracking central. The lower the tier, the more your own data is all there is.

Check yourself

2 questions before you move on

  1. 1.Which tier does topical GHK-Cu sit in, and why?

  2. 2.What does tier 4, "practitioner experience only", actually mean for you?

Every lesson here is free to read, and it stays free. Your own schedule, vials and log live in the app: Claritide for iPhone.