Doxycycline Hyclate and negative side effects

i took my first dox tablet, 50mg. It is to treat adult acne. i am taking it because i am trying to get pregnant and this pill apparantly does not prevent that. I don't want to get a yeast infection from it because it is an antibiotics. The doctor told me that i wouldn't because it is a low dose. I am still scared. Reading all of these negative side effects that people have experienced makes me very concerned. How do we find out how safe something really is?

I have experienced negative side effects from doxycycline. I have had chest pains, headaches, and nausea. It is perscribed for a sinus infection but I think I would rather deal with the pain of sinus pressure than the side effects.

I began taking this medication at 100mg twice daily for a sinus infection and have experienced negative side effects. I actually experienced side effects and then decided to check the side effect listings for the drug online and they defintly match. I have experienced extreme dehydration, nauseau, headache, disorientation, drowsiness, and stomach pain. I have not experienced vommitting but have felt close to it. I have also experienced a loss of appetite.