CarlaRPh_TPA said:

Two pharmacies quoted me last year, one describing itself as 503A and one as 503B, and I assumed 503B just meant bigger until both stopped within…

Vendor communication red flags for compounded supply:

• Won't provide COA before purchase — walk away
• Claims "100% pure" without analytical data — unrealistic
• No physical address or phone number — accountability matters
• Pushes you to buy more than you need — pressure tactics
• Won't answer questions about their compounding process — transparency is key
• Payment only via crypto or wire transfer — legitimate pharmacies accept cards

A legitimate compounding pharmacy operates like a healthcare business, not a gray market dealer.

A narrower follow-up, since the general answer is now clear:

What actually distinguishes 503A from 503B, in terms of what each may make and from what starting material?

lucas_SP_BR said:

Vendor communication red flags for compounded supply: Won't provide COA before purchase — walk away Claims "100% pure" without analytical data —…

Price comparison for compounded supply across sources I've used:

I use the 503B option — best balance of quality, cost, and legality. The brand price is insane but insurance can help if you qualify.

Closing the loop on my own question.

The bulks-list asymmetry was the piece I had missed entirely. It explains why one of my two pharmacies is still arguing it can supply and the other simply stopped.

hyun_seoul said:

Price comparison for compounded supply across sources I've used: Source Monthly Cost Type Purity Verified Brand (Ozempic) $1014 FDA-approved N/A…

Agreed, and the enforcement dates were staggered by category — 503A first, 503B a few weeks later — because outsourcing facilities have manufactured inventory and clinic contracts to unwind while a 503A makes to order.