For most people, antibiotic-associated diarrhea causes mild signs and symptoms, such as:

• Loose stools
• More-frequent bowel movements

Antibiotic-associated diarrhea is likely to begin about a week after you start taking an antibiotic. Sometimes, however, diarrhea and other symptoms don't appear until days or even weeks after you've finished antibiotic treatment.

Clostridium difficile infection

C. difficile is a toxin-producing bacterium that can cause a more serious antibiotic-associated diarrhea. In addition to causing loose stools and more frequent bowel movements, C. difficile infection can cause:

• Lower abdominal pain and cramping
• Low-grade fever
• Nausea
• Loss of appetite

Why antibiotic-associated diarrhea occurs isn't completely understood. It's commonly thought to develop when antibacterial medications (antibiotics) upset the balance of good and bad bacteria in your gastrointestinal tract.

Nearly all antibiotics can cause antibiotic-associated diarrhea. Antibiotics most commonly involved include:

• Cephalosporins, such as cefdinir and cefpodoxime
• Penicillins, such as amoxicillin and ampicillin

C. difficile infection

When antibiotics upset the balance of bacteria in your digestive system, the bacteria C. difficile can quickly grow out of control. C. difficile bacteria create toxins that attack the lining of the intestine. The antibiotics most commonly linked to C. difficile infection include fluoroquinolones, cephalosporins, penicillins and clindamycin.

Antibiotic-associated diarrhea can occur in anyone who takes an antibiotic. But you're more likely to develop antibiotic-associated diarrhea if you:

• Have had antibiotic-associated diarrhea in the past
• Have taken antibiotic medications for an extended time
• Are taking more than one antibiotic medication

One of the most common complications of any type of diarrhea is extreme loss of fluids and electrolytes (dehydration). Severe dehydration can be life-threatening. Signs and symptoms include a very dry mouth, intense thirst, little or no urination, and weakness.