A few things to know about Mestinon...

it effectively lasts about 4 hours - - so if you are taking it twice a day - you are probably 'running on empty' for some hours of the day

it's absolutely best to take it with some food - candy bars don't really qualify, the sugar alone could make anyone anxious

For reasons that I do not know, I was pretty sensitive to Mestinon in the beginning and could 'feel it' kick in...and I was kind of anxious about what I was feeling. After almost 18 months of taking it, I rarely get that feeling anymore even though I now take higher doses

As far as how do you know if it's working? Mostly I know when it isn't - not when it is. If I need more (like when it is getting close to time to take it) - I'm still functioning fine. I'm just exerting more will power to do whatever I'm doing! I could keep going without it - but by the end of the day I would be droopy and tired...and I would be concentrating and using two hands to get the gallon of milk out of fridge - instead of just grabbing the milk!!