<s>[INST] Hello. My doctor prescribed me fosfomycin for cystitis but I haven t taken it yet because I m scared of the side effects. I was wondering if it has any more serious side effects aside from the possible ones usually related to taking antibiotics. Thank you. [/INST] Hello, All antibiotics have side effects, but serious side effects are rare, and fosfomycin does not have any more risk than other antibiotics.  Most of the side effects of fosfomycin are not serious and go away after stopping it, and include headache, dizziness, diarrhea, and nausea.  Especially since you would probably only take it for a few days with cystitis, I wouldn't be concerned, and you can take them without worrying. Hope I have answered your query. Let me know if I can assist you further. Take care Chat Doctor.  </s>