Which antibiotic causes diarrhea? Understanding the risks and management

October 12, 2025 •

4 min read

Did you know that up to 1 in 5 people who take antibiotics will experience antibiotic-associated diarrhea? This occurs when the medication disrupts the natural balance of gut bacteria, leading to digestive upset. Certain antibiotic classes are far more likely to cause this side effect than others, with some carrying a significant risk for more severe conditions like C. difficile infection.

Quick Summary

Many antibiotic classes, such as clindamycin, penicillins, and cephalosporins, can disrupt gut bacteria and lead to diarrhea. This can range from mild to a severe C. difficile infection, depending on the antibiotic and individual risk factors.

Key Points

High-Risk Antibiotics: Clindamycin, fluoroquinolones, cephalosporins, and carbapenems are most commonly associated with a high risk of diarrhea and C. difficile infection.
Diarrhea Mechanism: Antibiotics disrupt the natural balance of gut bacteria, allowing opportunistic pathogens like C. difficile to overgrow and cause inflammation and diarrhea.
Mild vs. Severe: Most cases of AAD are mild and resolve after antibiotic treatment ends, but severe cases, particularly those caused by C. difficile, require immediate medical attention.
Management Strategies: Supportive measures like hydration, a bland diet (BRAT), and probiotics can help manage symptoms and restore gut health.
Seek Medical Help: If you experience severe symptoms like high fever, bloody stool, or persistent diarrhea, it is crucial to contact a healthcare provider immediately to rule out serious complications.
Probiotic Use: Strains like Saccharomyces boulardii and Lactobacillus rhamnosus GG have shown efficacy in preventing AAD, but consultation with a doctor is advised.

The Gut Microbiota and Antibiotic Disruption

Antibiotics are powerful medications that kill or inhibit the growth of bacteria. While they are crucial for treating bacterial infections, they are non-discriminatory and can also harm the trillions of beneficial bacteria that live in our gastrointestinal (GI) tract, collectively known as the gut microbiota. This delicate ecosystem plays a vital role in digestion, nutrient absorption, and protecting the body from opportunistic pathogens.

When this balance is disturbed by antibiotics, it creates an opportunity for harmful, drug-resistant bacteria to proliferate. This overgrowth can lead to inflammation and irritation of the colon, resulting in diarrhea. In milder cases, the diarrhea is self-limiting and resolves once the antibiotic treatment is finished. However, in more severe instances, the opportunistic pathogen Clostridioides difficile (C. difficile) can take hold, producing toxins that cause a more serious and potentially life-threatening condition called C. difficile infection (CDI).

High-Risk Antibiotics for Diarrhea and C. Difficile Infection

Not all antibiotics carry the same risk of causing diarrhea. The risk level is generally higher for broad-spectrum antibiotics, which target a wide range of bacteria, both good and bad. The following classes and specific drugs are most commonly associated with a high risk of antibiotic-associated diarrhea (AAD) and CDI:

Clindamycin: Considered one of the highest-risk antibiotics for causing CDI, with some studies showing an odds ratio significantly higher than for no antibiotic exposure. It was historically responsible for outbreaks of pseudomembranous colitis.
Fluoroquinolones: This class includes common drugs like ciprofloxacin (Cipro) and levofloxacin (Levaquin) and is associated with a high risk of both AAD and CDI.
Cephalosporins: Broad-spectrum cephalosporins such as ceftriaxone and cefdinir are also frequently linked to CDI. Studies have shown that prescribing guidelines focusing on reduced use of these antibiotics can lower CDI incidence.
Carbapenems: Used for severe, multidrug-resistant infections, carbapenems like meropenem carry a high risk of causing CDI.

Moderate to Lower Risk Antibiotics

While high-risk antibiotics deserve extra caution, other commonly prescribed medications can also trigger diarrhea, albeit with a lower incidence or severity:

Penicillins: Common penicillins like amoxicillin and ampicillin, as well as the combination drug amoxicillin/clavulanate, are known to cause diarrhea by altering gut microbiota.
Macrolides: This class includes azithromycin and clarithromycin. Macrolides can cause diarrhea through stimulation of intestinal motility, in addition to disrupting gut bacteria.
Other: Other microorganisms can contribute to non-C. difficile AAD, including Klebsiella oxytoca, which can cause hemorrhagic colitis.

Managing and Preventing Antibiotic-Associated Diarrhea

Managing AAD depends on its severity. For mild cases, it is often a matter of supportive care, while more severe cases, especially CDI, require specific medical intervention.

Practical Strategies

Hydration: Drink plenty of fluids to replace lost body water and electrolytes, especially with frequent, watery stools. Good options include water, broth, or electrolyte replacement drinks.
Dietary Adjustments: Consider adopting a bland, low-fiber diet, often referred to as the BRAT diet (Bananas, Rice, Applesauce, Toast). Temporarily avoid spicy, fatty, high-fiber, and highly acidic foods, as they can further irritate the digestive system.
Probiotics: Taking probiotics can help restore the balance of beneficial bacteria in the gut. Evidence suggests that strains like Lactobacillus rhamnosus GG and Saccharomyces boulardii are particularly effective in preventing AAD. Probiotics can be taken in supplement form or by consuming fermented foods like yogurt with live cultures. However, it's best to consult with a healthcare provider on the best type and timing.
Avoid Anti-Diarrheal Medications: For severe cases, especially if CDI is suspected, anti-diarrheal medications are generally not recommended as they can prolong exposure to toxins. Always consult a doctor before using them.

Comparison of Antibiotic Classes and Diarrhea Risk


Antibiotic Class	Examples of Drugs	Diarrhea Risk Level	Note on C. difficile Risk
High Risk	Clindamycin, Ciprofloxacin, Levofloxacin, Ceftriaxone, Meropenem	Highest	High odds of causing C. difficile infection, especially with prolonged use.
Moderate Risk	Amoxicillin, Ampicillin, Azithromycin, Clarithromycin	Moderate	Still poses a risk for C. difficile but lower than high-risk classes.
Lower Risk	Metronidazole, Vancomycin (oral), Tetracyclines	Low to Moderate	Oral vancomycin is used to treat CDI. Tetracyclines have a lower association with CDI.

What to Do If You Experience Severe Symptoms

While mild AAD is common, severe symptoms can indicate a more serious condition like CDI. You should contact a healthcare professional immediately if you experience any of the following:

Diarrhea that is severe or occurs more than three times a day.
Diarrhea that lasts more than two days after stopping the antibiotic.
Fever and abdominal cramps.
Blood or pus in your stool.
Symptoms of dehydration, such as intense thirst, reduced urination, or dizziness.

Conclusion

Antibiotic-associated diarrhea is a common and predictable side effect of antibiotic use, resulting from the disruption of the gut's normal microbial balance. While most cases are mild, certain broad-spectrum antibiotics carry a higher risk of causing severe diarrhea, including potentially life-threatening C. difficile infection. Understanding which antibiotic causes diarrhea and the steps to manage and prevent it is key to protecting your health during treatment. By maintaining proper hydration, making dietary adjustments, considering probiotics, and seeking medical attention for severe symptoms, you can mitigate the risks and promote a healthier gut.

Note: For more information on responsible antibiotic use, visit the CDC's Antibiotic Use website.

Frequently Asked Questions

Clindamycin is considered to be one of the antibiotics with the highest risk of causing C. difficile infection. Other broad-spectrum antibiotics, like fluoroquinolones and cephalosporins, also carry a significant risk.

The main cause is the disruption of the normal gut microbiota by antibiotics. This imbalance can lead to an overgrowth of harmful bacteria, like C. difficile, which produce toxins that damage the intestinal lining and cause inflammation.

You should contact a doctor immediately if you have frequent and severe watery diarrhea, abdominal pain and cramping, fever, or blood or pus in your stool. These are symptoms of a more serious infection.

You should not take anti-diarrheal medications without consulting your doctor, especially if you suspect a C. difficile infection. These drugs can worsen the condition by preventing your body from flushing out the harmful bacteria and toxins.

Probiotics introduce beneficial bacteria to your gut, which can help re-establish a healthy microbial balance. Research suggests that certain strains, such as Saccharomyces boulardii and Lactobacillus rhamnosus GG, are particularly effective in preventing AAD.

For most people with mild cases, the diarrhea is self-limiting and resolves within a few days of stopping the antibiotic. However, more serious infections, like CDI, may require additional treatment.

While experiencing diarrhea, focus on bland, low-fiber foods like bananas, rice, applesauce, and toast. Avoid spicy, fatty, and highly acidic foods, as well as dairy products, which can sometimes aggravate symptoms.