bladder infection
"I have had many bladder infections in my lifetime and twice was prescribed nitrofurantoin.  Both times I took this medication I got a fever and was really lightheaded, had bad diarrhea, and was dehydrated severely probably because I had to force myself to eat and drink due to severe nausea on top of the diarrhea.  My bladder infection symptoms didn't improve either.

The first time I took this medication I just assumed the symptoms were from my bladder infection getting worse and not improving.  Either way I ended up passing out at work and being taken by ambulance to the hospital for severe dehydration.
The second time I took the medication(after I told my doctors it didn't work the first time and they convinced me to try it again) same."