Antibiotic-associated diarrhea warning: The use of almost all antibiotics, including cephalexin, can cause a reaction that leads to diarrhea. In addition to diarrhea, this reaction can cause severe inflammation of your colon. Severe cases of this reaction can be fatal (cause death).

Is Keflex a dangerous drug?

However, there are a few risks associated with Keflex. If Keflex is used too long or too often, it could cause a yeast infection or oral thrush. Keflex shouldn’t be used with narcotic pain medicines because it could cause certain gastrointestinal symptoms to get worse.

How common are Keflex side effects?

Diarrhea is the most common side effect of Keflex, occurring in 4% of cases in one study. While nausea incidence alone was not defined in the study, vomiting was experienced by 0.5% of individuals.