Understanding Which Antibiotics Cause Diarrhea

October 14, 2025 •

4 min read

Approximately one in five people who take antibiotics experience antibiotic-associated diarrhea (AAD). This common side effect, which can range from mild to severe, occurs when antibiotics disrupt the natural balance of gut bacteria. Understanding which antibiotics cause diarrhea can help patients and doctors manage risks effectively.

Quick Summary

An overview of antibiotic-associated diarrhea, its causes, and the specific classes of antibiotics most likely to trigger it. Discusses the link to Clostridioides difficile and outlines strategies for prevention and management.

Key Points

High-Risk Antibiotics: Clindamycin, cephalosporins, fluoroquinolones, and certain penicillins and macrolides carry a higher risk of causing diarrhea due to their broad-spectrum effects.
Microbiome Disruption: Antibiotic-associated diarrhea is caused by the disruption of the normal, healthy bacteria in the gut, which can lead to metabolic imbalances or overgrowth of pathogens.
C. difficile Risk: In serious cases, the overgrowth of Clostridioides difficile bacteria can lead to severe diarrhea, cramping, and fever, requiring immediate medical attention.
Hydration is Key: Drinking plenty of fluids, especially water and electrolyte solutions, is essential for managing diarrhea and preventing dehydration.
Consult Before Antidiarrheals: Over-the-counter antidiarrheal medications should be avoided unless approved by a doctor, as they can worsen infections like C. difficile.
Probiotics for Prevention: Probiotics, taken with a doctor's approval, might help restore gut bacteria balance, though their effectiveness is debated, and they are not for immunocompromised patients.

What is Antibiotic-Associated Diarrhea?

Antibiotic-associated diarrhea (AAD) is a condition marked by loose, watery stools occurring three or more times a day, often starting shortly after or even weeks after taking an antibiotic. The primary cause is the disruption of the healthy bacteria (microbiome) in the gastrointestinal tract. While antibiotics are designed to kill harmful, infection-causing bacteria, they are not selective and also eliminate many beneficial bacteria. This disruption can upset the delicate balance of the gut, leading to several possible issues:

Opportunistic Pathogen Overgrowth: With fewer beneficial bacteria to keep them in check, certain harmful bacteria, particularly Clostridioides difficile (C. diff), can multiply rapidly and produce toxins.
Metabolic Imbalances: The loss of certain gut microbes can disrupt metabolic functions, such as the fermentation of carbohydrates and the metabolism of bile acids, leading to osmotic diarrhea.

For many, AAD is a mild and self-limiting condition that resolves after stopping the antibiotic. However, in more severe cases, it can indicate a C. difficile infection (CDI), which requires medical attention.

High-Risk Antibiotics for Diarrhea

While nearly all antibiotics have the potential to cause diarrhea, some are more frequently associated with this side effect due to their broad-spectrum activity. The following are some of the most common high-risk classes and examples:

Clindamycin: A lincosamide with a notoriously high risk of causing severe, persistent diarrhea, including a high incidence of C. difficile infection.
Cephalosporins: A large family of broad-spectrum antibiotics, with examples like cefdinir (Omnicef) and cefpodoxime often cited for their association with AAD.
Fluoroquinolones: These potent, broad-spectrum antibiotics, such as ciprofloxacin (Cipro) and levofloxacin (Levaquin), are linked to an increased risk of AAD, including serious C. diff infections.
Penicillins: Particularly the broader-spectrum versions like amoxicillin, and especially amoxicillin/clavulanate (Augmentin), are known to cause diarrhea.
Macrolides: Antibiotics like erythromycin and azithromycin can cause AAD, often by directly stimulating gut motility.
Carbapenems: Powerful beta-lactam antibiotics, such as meropenem, are used for more severe infections and carry a significant risk of AAD and CDI.

The Serious Threat of Clostridioides difficile

In some cases, the gut flora imbalance allows a specific bacterium, Clostridioides difficile (formerly Clostridium difficile), to flourish. C. diff produces toxins that cause inflammation in the colon, leading to symptoms more severe than typical AAD.

Symptoms of a C. difficile infection (CDI) include:

Frequent and severe watery diarrhea
Pain and cramping in the lower belly
Low-grade fever
Nausea
Loss of appetite

If you experience these symptoms, especially with blood or pus in the stool, it is crucial to contact a healthcare provider immediately, as CDI can lead to severe dehydration and other complications.

Lower-Risk Antibiotics for Diarrhea

Some antibiotic classes generally have a lower incidence of causing diarrhea. These are not completely risk-free but may be preferable for patients with a history of AAD. Examples include:

Aminoglycosides: Such as gentamicin, tobramycin, and amikacin.
Metronidazole: This antibiotic is ironically also used to treat C. difficile infections.
Nitrofurantoin: Often used for urinary tract infections.

Comparison of Antibiotic Risk Levels


Antibiotic Class	Examples	Risk of Diarrhea	Common AAD/CDI Risk Factor	Notes
High Risk	Clindamycin, Cefdinir, Ciprofloxacin	High	Yes	Disrupts normal flora, allows for opportunistic pathogen overgrowth
High-Moderate Risk	Amoxicillin, Amoxicillin/Clavulanate	High	Yes	Broad-spectrum, disrupts normal flora
Moderate Risk	Erythromycin, Azithromycin	Moderate	No (less common)	Can increase gut motility, but lower CDI risk
Low Risk	Metronidazole, Gentamicin, Nitrofurantoin	Low	No	Less disruptive to overall gut flora; metronidazole is used for C. diff

Managing and Preventing AAD

If you are concerned about AAD, discuss it with your healthcare provider. Here are some strategies for prevention and management:

Before and During Treatment

Consider a Probiotic: Discuss with your doctor whether a probiotic supplement, or incorporating probiotic-rich foods like yogurt, might help maintain gut flora balance. However, evidence is mixed, and caution is advised for immunocompromised individuals.
Stay Hydrated: Drink plenty of fluids, including water and electrolyte-rich drinks like broth, to replace lost fluids.
Limit Certain Foods: Temporarily avoid dairy, fatty foods, and spicy foods, as they can exacerbate symptoms.

During Diarrhea

Continue Antibiotics: Unless advised by your doctor, do not stop your prescribed course of antibiotics, even if you experience mild diarrhea. Stopping prematurely can lead to recurring infections.
Avoid Antidiarrheals: Do not take over-the-counter anti-diarrheal medications without consulting your doctor. They can prolong the presence of toxins in your gut and worsen infections like CDI.
Contact Your Doctor: If diarrhea is severe, bloody, or accompanied by fever or abdominal pain, contact your doctor immediately to rule out a C. difficile infection.

Conclusion

Understanding which antibiotics cause diarrhea is crucial for recognizing and managing this common side effect. High-risk medications like clindamycin, cephalosporins, and fluoroquinolones can severely disrupt the gut microbiome, sometimes leading to a serious C. difficile infection. By discussing your concerns with your healthcare provider, taking appropriate preventative measures like considering probiotics (under supervision), and recognizing when to seek medical help for severe symptoms, you can better navigate antibiotic treatment safely.

For more information on antibiotic side effects and safety, you can consult reputable sources like the Mayo Clinic.

Frequently Asked Questions

Antibiotic-associated diarrhea (AAD) is the passing of three or more loose, watery stools a day following antibiotic treatment. It occurs when antibiotics disrupt the balance of beneficial bacteria in the gut, allowing harmful organisms to overgrow or causing other metabolic issues.

Antibiotics with a broader spectrum, meaning they kill a wider range of bacteria (including good bacteria), are more likely to cause diarrhea. Classes like clindamycin, cephalosporins, and fluoroquinolones are particularly known for disrupting the gut's normal flora.

Yes, it is possible for diarrhea and other symptoms to appear days or even weeks after you have finished your antibiotic treatment. This is often due to a lingering imbalance in your gut microbiome.

You should call your doctor if diarrhea lasts more than two days, or if you experience severe symptoms like high fever, severe abdominal pain, or blood in your stool. These can be signs of a more serious C. difficile infection.

Some research suggests that certain probiotics might help prevent or reduce the severity of AAD, but the evidence is mixed. You should always talk to your doctor before starting any probiotic regimen, especially if you have a weakened immune system.

To help manage symptoms, it is best to temporarily avoid dairy products, spicy foods, fatty foods, and high-fiber foods. Focus on bland foods and ensure you drink plenty of fluids.

You should not take over-the-counter anti-diarrheal medications without consulting your doctor first. In cases of C. difficile infection, these medications can be harmful, as they can prevent your body from clearing the toxins produced by the bacteria.