Seeing a lot of confusion about PeptideMeter Analytics' vendor rating system, so let me break it down clearly. PeptideMeter uses a letter grade system (A through E) to rate vendors based on aggregated test data. Here's how it works: Grade A — Excellent (95%+ purity, accurate dosing, sterility pass) - Vendor consistently delivers pharmaceutical-grade product - Multiple passing test results across different batches - Dosing accuracy within ±10% of label claim - Only a handful of vendors achieve this rating Grade B — Good (90-95% purity, minor dosing variance) - Reliable vendor with generally good quality - May have occasional batch-to-batch variation - Dosing within ±15% of label claim - Most established vendors fall here Grade C — Acceptable (85-90% purity, moderate issues) - Product is generally what it claims to be but quality is inconsistent - Some batches may be underdosed - "Use with caution" territory Grade D — Poor (75-85% purity, significant issues) - Frequent quality problems - Underdosing common - Not recommended but not outright dangerous Grade E — Fail (<75% purity, identity failures, contamination) - Vendor has failed critical tests - Products may be mislabeled, severely underdosed, or contaminated - Avoid at all costs These grades are dynamic — they update as new test data comes in. A vendor with a B rating can move to A with more positive results, or drop to C with bad ones. 📊

This is really helpful. Where do I actually see these ratings? Is there a list on PeptideMeter's website?

Yes — PeptideMeter publishes their vendor ratings on their website (peptidemeteranalytics.com) and they also share updates on their social media. They maintain a searchable database of tested vendors. You can also find their ratings mirrored in our Vendor Directory here on CompoundTalk. The mod team updates vendor listings with the latest PeptideMeter grades whenever new results drop. Keep in mind that PeptideMeter only rates vendors they've actually tested. If a vendor isn't in their system, it doesn't mean they're bad — it just means they haven't been tested yet. Absence of data ≠ evidence of quality.

Let me add some nuance that the letter grades don't capture: The rating is an aggregate. A vendor with a "B" rating might have: - 3 tests at 94-96% purity (A-level) - 1 test at 88% purity (C-level) - Average pulls them to B So always look at the individual test results behind the grade, not just the letter. A consistent B is very different from a volatile B that swings between A and D. Compound-specific variation matters too. A vendor might get: - Grade A for semaglutide - Grade C for tirzepatide - Grade B for retatrutide This could mean their sema synthesis/sourcing is excellent but their tirz is inconsistent. PeptideMeter does note compound-specific results in their detailed reports. > Don't just look at the letter — dig into the data behind it. 🔎

How does PeptideMeter decide which vendors to test? Do they take requests?