Altitude sickness

It would probably be foolish to say one cannot get altitude sickness on this trek, but you would certainly have to be remarkably sensitive to feel any effects below 3000m. And this trek doesn’t go much above that. 

Additionally it does not stay at even those modest altitudes for any length of time, so it is always possible to sleep at a lower level than the day’s high point. 

If you already know you are highly susceptible, then I’d consider asking yourself why on earth you are trekking in Nepal at all. In any case it is always sensible to ensure you have enough time, and not to rush.