How long does it take for cephalexin side effects to go away?

Most cephalexin side effects are mild and should go away once your prescription is finished. This may include symptoms such as diarrhea, nausea, stomach pain, dizziness, fatigue, and headache. But there are some serious side effects to be aware of. Rare but serious risks include Costridioides difficile diarrhea, allergic reactions, liver problems, kidney problems, low blood cell counts, confusion, agitation, an increased risk of bleeding, and seizures. Side effects like these warrant medical attention; you shouldn't wait for them to go away on their own. View original source