How can one tell the difference between antibiotic side effects and colitis?

Not always different: Colitis can be a bad side effect of taking antibiotics. Talk to your doctor if you have excessive diarrhea that does not get better or if the stools become bloody stool. Drink lots of fluids to keep from getting dehydrated. Call your physician if this condition worsens and you become weak and dehydrated.

Difficult: If no recent antibiotics that is clear. Both can cause diarrhea.