Adding the clinical framing, because it changes how the question reads.

My vendor review relevant to certificates of analysis: ordered 3 times from my current compounder. Consistency has been excellent.

Shipping: Next-day with cold pack
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 99.0% average across orders (Janoshik verified)
Customer service: Responsive within 2 hours
Price: $136/month for semaglutide 1.7mg equivalent

DoseLogDan said:

Mass spectrometry confirmation for certificates of analysis: beyond HPLC purity, mass spec tells you the molecule's exact molecular weight.

Thank you for spelling out the reasoning rather than just the conclusion. Taking it to my next appointment.

From the other side of the consultation, briefly.

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members. Across 60 submitted tests:

• 85% tested at ≥98% purity
• 10% tested at 95-98% purity
• 5% tested at <95% purity (concerning)

The vendors with consistently high purity results are listed in the Vendor Directory. We update monthly based on new community submissions.

Dr.GutHealth said:

Community-verified vendors for certificates of analysis: I maintain a spreadsheet of Janoshik-verified test results submitted by community members.

Second this. Nothing to add that would improve it.

Moderator note: two posts asking for a source have been merged into one. Please search the thread before asking again. Carry on.