I'm one week into minoxidil (I'm not always using it twice a day) But I just washed my hair and didn't see a single strand.
Shedding's a good thing.
I think what may be the cause for me is, I've been using finasteride and spironolactone which reduced shedding anyway.
Since minoxidil only sheds hairs in the (telogen?) phase, I think finasteride and spironolactone have reduced the amount of hairs in this stage by reducing the DHT reaching them, and 'hopefully' this will mean I won't shed many hairs on minoxidil, while still getting some results.
Fingers crossed anyway.