PeptideMeter selects vendors through several channels: 1. Community requests — if enough people ask about a specific vendor, PeptideMeter will prioritize testing them 2. Their own purchasing — PeptideMeter buys product directly from vendors as a regular customer (blind purchase, vendor doesn't know it's for testing) 3. Community-submitted samples — members can send samples from their own orders 4. Vendor opt-in — some vendors actually volunteer for PeptideMeter testing to prove quality (these are marked as "vendor-submitted" vs "blind purchase") The blind purchases (#2) are the most valuable because the vendor had zero knowledge that product would be tested. It's a true random sample of what a regular customer would receive. Vendor-submitted samples (#4) are noted separately in the database because, as we've discussed in the Janoshik threads, vendor-submitted samples can be cherry-picked.

Important context: PeptideMeter's rating system is relatively new — they launched in 2025 and have been building their database since then. They don't have as much historical data as Janoshik, but they're growing fast. Current database size (approx): - ~40 vendors rated - ~200+ individual test results - Focus primarily on GLP-1 peptides (semaglutide, tirzepatide, retatrutide) Distribution of current ratings: - Grade A: ~5 vendors - Grade B: ~12 vendors - Grade C: ~10 vendors - Grade D: ~8 vendors - Grade E: ~5 vendors The fact that only ~12% of tested vendors achieve an A rating tells you something about the current state of the market. Quality is not universal.

One thing I appreciate about PeptideMeter's system is the transparency of methodology. They publish: - Exactly which tests were run (HPLC purity, identity, quantitative, sterility) - The raw data (chromatograms, peak tables) - The specific criteria for each grade - Whether the sample was blind-purchased or vendor-submitted - The date of testing and batch information if available This means you can audit their work. If you disagree with a grade, you can look at the underlying data and form your own opinion. That's how it should be. Compare this to some other "rating" systems that just say "recommended" or "not recommended" with zero supporting data. PeptideMeter shows their work. 📋

Can a vendor's grade change? Like if a Grade D vendor improves their manufacturing, can they move up?

Absolutely. Grades are dynamic and update with new data. PeptideMeter uses a weighted system where recent results count more than older ones. So if a vendor had a bad batch 6 months ago (Grade D result) but their last 3 tests have been Grade A quality, their overall rating would improve significantly. I've seen it happen both ways: - One vendor went from C to A over 6 months after apparently switching to a better synthesis supplier - Another vendor dropped from B to D after what appeared to be a quality control breakdown This is actually one of the strengths of the rating system — it captures vendor trajectory, not just a static snapshot. A vendor that's improving is very different from one that's declining, even if their current grade is the same. The market evolves, and the ratings evolve with it. Keep checking for updates. ⬆️⬇️