A standard ket microdose isn’t established. Microdosing other psychedelics like psilocybin or LSD is typically about one-tenth of a full or “macro” dose.
We know from studies of intravenous ketamine treatments for mental health that different people respond to different doses. Many clinics work with 0.3-0.5mg per kg. However, some people respond to 0.1 mg per kg. Another might need... https://psychedelictrippyworld.com/product/buy-ketamine-crystals-online/