How do you approach your teachers?

I have been missing a few of my classes here lately because Im struggling with some issues (I think it might be dehydration) how do I explain this to my professors? Im trying to keep up with all my work outside of class but don't want to get kicked out of class or have my grade lowered because I'm missing class. Should I let them know about my WLS, and that Im having complications?

I didn't tell them about my wls... but I told them I recently had major surgery and suffering some complications.  I made sure to do my work and handed it in via email or however they asked for it.

You don't need to tell them if you don't want to.  If you are working with your surgeon or doctor for whatever is going on, simply have them write a note saying that you are having medical problems.  At the college I attend it is school policy to make professors work with you if you have a note from a doctor excusing absences.  If a note like that isn't enough for your professors, look up your school's policy concerning medical conditions / absences. If you don't mind me asking - what's happening?  I would hate to think that you are suffering from something WLS related.  Whatever it is, I hope you're feeling 100% better soon! 

You do not need to tell them.  I had minor problems following my surgery which kept me out of work and school for about a week and I just told everyone that I had major surgery and just need some more time to recover.  Everyone seemed to understand.  Most Uni's can not fail you or lower your grade just because you miss classes(with a dr. excuse).  As long as you do the work you should be fine.  Although in some of my classes missing a lecture is like the worst thing.  Do you have any one you can get notes from?? That would probably help too.  And let your professor know that you are getting notes from somebody.  Make sure that he/she know that you are truly making an effort.   Good luck!  Hope you get to feeling better~!