Dr.AddMedPHL said:

Inter-laboratory variation comes from real methodological differences, not sloppiness: which reference standard was used and how it was itself…

This is exactly what I could not find anywhere else. Adding it to my notes with a link back to this thread.

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

Vendor quality matters when discussing certificates of analysis. I've tested my last 6 batches through Janoshik and purity has ranged from 98.9% to 100.3%. Consistency is key.

For anyone new: always request the COA, and consider independent verification. The $300 for a Janoshik test is worth the peace of mind.

andrew_nyc said:

I tested my certificates of analysis batch through Janoshik — 97.6% purity.

COA red flags for certificates of analysis — here's what to look for when reviewing a Certificate of Analysis:

• No HPLC data: If there's no chromatography graph, it's not a real COA
• Exact 100% purity: Suspicious — real testing always shows slight variation
• No batch number: Can't trace back to specific production
• No endotoxin testing: For injectables, this is essential
• Template looks like it was made in Word: Professional labs have standardized formats

I have seen fake COAs that are literally photoshopped. Always verify independently if possible.

CarlaRPh_TPA said:

They are not contradictory, they measure different things, and this is the single most common misreading of a certificate.

My vendor review relevant to certificates of analysis: ordered 6 times from my current compounder. Consistency has been excellent.

Shipping: 3-day with temperature monitor
Packaging: Professional, discreet, proper labeling with lot/batch numbers
Purity: 97.7% average across orders (Janoshik verified)
Customer service: Responsive within 1 hours
Price: $135/month for semaglutide 2.4mg equivalent

Moderator note: a post naming a supplier has been edited. Discuss suppliers in the review sections, not here.