Ceftriaxone is a cephalosporin (SEF a low spor in) antibiotic. It works by fighting bacteria in your body. Ceftriaxone is used to treat many kinds of bacterial infections, including severe or life-threatening forms such as meningitis.Ceftriaxone may also be used for purposes not listed in this medication guide.ntibiotic medicines can cause diarrhea, which may be a sign of a new infection. If you have diarrhea that is watery or has blood in it, call your doctor. Do not use any medicine to stop the diarrhea unless your doctor has told you to.