i ordered 12.5 mcg to go and started with 1 spray.
saw nothing and over the course of a week, kept adding a spray until i saw difference.
this is in a work environment with anywhere from 30 - 60 people at a time, leaving and being replaced with fresh victims.
im 38, and it took until i got to 62.5 before i saw reaction enough that i could not deny its influence.
i feel more comfortable in its effectiveness at 100 mcg or higher.
150mcg has been my limit before it drops off.
of course this may be different from your experience.