How to Read a Peptide Certificate of Analysis (COA)
If you’re sourcing research peptides, the Certificate of Analysis (COA) is the single most important document a vendor can provide. Here’s how to actually read one.
What a COA Tells You
A COA is a lab report confirming what’s actually in a given batch of product. At minimum, a legitimate COA should show:
• Identity confirmation — confirms the compound is what it claims to be (not just “something similar”)
• Purity percentage — the proportion of the sample that is the target compound, versus impurities or degradation products
• Fill/quantity accuracy — whether the actual peptide content matches the labeled amount (e.g., a vial labeled 10mg should test close to 10mg)
• Batch or lot number — ties the COA to a specific production run, not just the product line in general
Red Flags to Watch For
• A single COA reused across every batch or restock — purity and fill can vary batch to batch, so a COA should be tied to the specific lot you’re receiving
• No batch/lot number listed at all
• COAs from a lab with no independent verification process or public track record
• Purity claims with no supporting chromatogram or raw data reference
Why Independent Testing Matters
A COA is only as trustworthy as the lab (and process) behind it. Independent testing — where the lab has no financial relationship with the vendor — reduces the chance of skewed results. Publicly searchable COA databases add another layer of accountability, since results are visible beyond just the vendor’s own product page.
What to Do With This Information
Before ordering from any research peptide vendor:
1. Ask for the batch-specific COA, not a generic one
2. Confirm the lab is independent of the vendor
3. Check that purity and fill numbers are both reported, not just one
4. Look up the lab’s reputation or public database if available
Bottom Line
A COA is a tool for transparency — but only if it’s batch-specific, independently verified, and complete. Take the extra minute to actually read it before trusting a product page’s marketing claims.
