Any serious side effects to the anti biotic levofloxacin?

Not usually: But you have to be aware it commonly causes gastrointestinal upset. It can also change heart conduction so called QT prolongation. It can also weaken your tendons. Sometimes people will get an uncommon complication of infectious diarrhea, like from the c-diff bacteria. Again these tend to be quite uncommon and overall it's pretty well tolerated.