A compound with no published human studies at all. The available evidence comes entirely from animal or cell-culture work.

Evidence is predominantly from animal studies. Any human data is limited to small uncontrolled pilots. This describes the majority of compounds sold in research markets.

Genuine human trials exist but are limited in size and scope, typically Phase 1 or Phase 2. The compound is not approved.

Advanced human trials are under way or have reported results. The compound remains unapproved and is generally available only through the trial itself.

Substantial human trial evidence exists. Usually indicates the compound is approved somewhere for something, though not necessarily for the use it is marketed for.