Does doxycycline cause c diff?

It can but rarely: Almost any antibiotic can cause c. Difficile overgrowth and diarrhea or colitis. Vancomycin almost never does. Azithromycin and Doxycycline are among the antibiotics with the lowest risk.

C. difficile: Doxycycline can alter your colonic bacterial flora so that it allows clostridium difficile to grow out and its toxin then produces damage to the lining of the bowel resulting in diarrhea and worse. If you think this is happening see a doctor asap.