HPLC_Greg said:

I tested my certificates of analysis batch through Janoshik — 98.4% purity.

My HPLC chromatogram analysis for certificates of analysis — I sent my batch to Janoshik and here's what the results showed:

Main peak retention time: 16.5 minutes (consistent with semaglutide reference standard)
Peak purity: 99.5%
Related substances: 0.6% (single impurity at 10.3 minutes — likely a synthesis intermediate)
Mass spec: m/z 4113.5 (matches expected molecular weight)

This is a clean result. The mass spec confirmation is particularly important — it proves the molecule is actually semaglutide and not a substitution.

HPLC_Greg said:

I tested my certificates of analysis batch through Janoshik — 98.4% 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.

HPLC_Greg said:

I tested my certificates of analysis batch through Janoshik — 98.4% purity.

This is exactly what I could not find anywhere else.

Clinical perspective, offered as context rather than as advice. The honest answer is that the effect is real, the magnitude is contested, and the individual variation is larger than either. Those three things can all be true at once, and most arguments here are two people holding different parts of that.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

Closing the loop on my own question.

For the archive: it took about six weeks rather than the two I expected, and the difference between those two numbers was the whole of my problem.