Methodology

Most comparison sites hide how they work. We publish it. Here's exactly how every number on pepmg is produced — and how to check us.

current index built 37m ago · 2026-08-16T09:16:24.094Z

▸ 0 · Why this site exists

You've used the other kind of price list. You know the moves:

• A price with no date. Cheapest… as of when? If a list won't tell you when a price was checked, assume it wasn't. Every row here carries its capture time and a link to the exact page we pulled it from.
• A "Top 10" that's really an ad rate card. When ranking is for sale, the list is the product and you're the traffic. Our order is $/mgPrice divided by the milligrams of active compound — the like-for-like way to compare cost across different vial sizes.Price divided by the milligrams of active compound — the like-for-like way to compare cost across different vial sizes. arithmetic. There is no price for position — the homepage's live index shows our paid-placement count (zero), and pepmg currently links out to no vendor at all, so no row earns us anything.
• A "cheapest" number propped up by a bulk vial or a blend. A 100mg wholesale vial or a two-peptide combo will always "win" a naive sort. We flag both and keep them out of the headline comparison, so cheapest means cheapest-for-the-same-thing.
• A price that's wrong when you land. Nothing burns trust like clicking through to a different checkout number. We re-audit every vendor feed on a 8-hour cycle and a QC gate blocks the deploy if a shown listing goes stale.

None of that requires trusting us — every claim above is checkable on any row of the site. That's the whole idea.

▸ 1 · Collection — first-party, live-captured

Every price on this site is read directly from the vendor's own live store — the same public product feed their own storefront runs on — then cross-checked against a fresh fetch before publishing. No middlemen, no stale caches, no guesswork.

• We read public data only. We never log in, never accept site terms, never bypass a technical block, never collect personal data. We honor robots.txt and rate-limit politely with an identifying user agent pointing here.
• Every listing is timestamped with when and where we fetched it — shown inline on every row, with a link back to the source page we captured from.
• Prices are the vendor's current list price (a discount code may lower checkout further).

▸ 2 · Normalization (the hard part)

Raw vendor data is messy. We turn it into one comparable number — cost per milligram — and flag what shouldn't be compared head-to-head:

• Size parsing from titles/variants ("60mg", "2×5mg", mcg→mg).
• Discount-adjusted price when a public code applies.
• Blends separated, not hidden. A multi-compound product (e.g. BPC-157/TB-500) can't have an honest single-compound $/mg, so we keep it out of that ranking and show it in each compound's own clearly-marked "blends & stacks" section instead. (709 shown separately)
• Form-filtered — oral/nasal/topical variants are separated from standard injectable vials.
• Bulk flagged — wholesale vials (≥100mg) are marked so they don't masquerade as the retail "cheapest." (908 flagged)
• Statistical outlier guard — anything outside 0.2×–5× the compound's medianThe middle value in a sorted list — half the prices sit above it, half below.The middle value in a sorted list — half the prices sit above it, half below. $/mg is flagged, so one mispriced vial can't define the cheapest or the spreadThe highest $/mg divided by the lowest for the same compound — how widely its price varies across vendors.The highest $/mg divided by the lowest for the same compound — how widely its price varies across vendors. . (1721 flagged)

▸ 3 · Ranking (money can't move it)

Tables sort strictly ascending by $/mg. Bulk and outlier rows are de-emphasized and pushed below clean retail. No vendor can pay to move up. pepmg publishes no outbound vendor links right now, so no row on this site earns us a commission; the sort is the same $/mg arithmetic either way. See /disclosure.

▸ 4 · Continuous re-checking

A separate job re-fetches every first-party vendor on a schedule and compares the live price to what's published here. If a listing has gone dead or drifted, it's flagged for removal or refresh — so "captured 4h ago" stays true, not just true once. The whole index is also an open feed: /api/prices.json — every listing carries its vendor, fetch time, and the flags above. The per-listing vendor source URL is suspended from that feed while vendor links are off — the feed says so in meta.vendorLinks, and every other field is unchanged.

▸ 5 · What the receipt proves — and what it doesn't

Being honest about our limits is the point. A pepmg row proves exactly one thing: this was the vendor's listed price for this product at the time and source shown. It does not prove:

• PurityThe share of a sample that is the intended compound, usually reported as a percentage on a COA.The share of a sample that is the intended compound, usually reported as a percentage on a COA. or identity. We don't test product. Where a vendor publishes a Certificate of Analysis we'll link to it — labeled "vendor-published," because we didn't run the lab.
• Current price. Vendors reprice without notice — always confirm on their site before buying (the source link is right there).
• Checkout total. Our $/mg is the listed vial price; shipping, minimums, and payment surcharges are the vendor's, not ours.
• An endorsement. A cheaper $/mg is a cheaper number, not a recommendation. We sell nothing and ship nothing.

If a number looks wrong, the receipts are right there — click the source, check the math, and tell us at hello@pepmg.com. We'd rather be corrected than wrong.

▸ 6 · Vendor longevity — domain ageHow long the vendor's website domain has existed — from public registration records and the Wayback Machine. It's the domain's age, not proof of how long the business has run.How long the vendor's website domain has existed — from public registration records and the Wayback Machine. It's the domain's age, not proof of how long the business has run.

One of the few objective, hard-to-fake trust signals in this space is how long a vendor has actually been online. Outright scam shops rarely last; established stores have a reputation to protect. For each vendor we resolve two public facts:

• Domain registration date — from public registration records (RDAP/WHOIS): when the domain was first registered.
• First seen online — the earliest snapshot of the site in the Wayback Machine.

We show the earlier of the two as a rough "online since" as a longevity signal about a source, not scored into anything and not published per seller while vendor identity is suspended. Two honest caveats: it is the domain's age, not proof of how long the business has run — an aged domain can be bought or a brand rebranded — and it is a weak signal, so we never treat it as a safety verdict. It has no effect on the $/mg ranking; price is still the only sort, and no vendor can pay for placement.