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. 🔎
Last edited: Apr 24, 2026 at 1:07 AM