Can clarithromycin cause diarrhea? Understanding the Risks and Symptoms

October 12, 2025 •

3 min read

According to prescribing information, diarrhea is a common side effect reported in patients taking clarithromycin. This gastrointestinal upset, while often mild, is a known consequence of how this macrolide antibiotic can affect the balance of bacteria in the gut.

Quick Summary

Yes, clarithromycin can cause diarrhea. This occurs when the antibiotic disrupts normal gut bacteria, which can lead to mild digestive upset or, in rare cases, a serious C. difficile infection. Symptoms range from frequent loose stools to severe, watery, or bloody diarrhea. Management involves hydration and doctor consultation, especially for severe or persistent issues.

Key Points

Diarrhea is a common side effect of clarithromycin: Like many antibiotics, it can disrupt the natural balance of bacteria in the gut, leading to loose stools.
Monitor for severe symptoms: Distinguish between mild, temporary diarrhea and severe, persistent, or bloody stools, which could signal a serious C. difficile infection.
Stay hydrated during mild diarrhea: Focus on drinking plenty of water, broth, and electrolyte solutions to prevent dehydration.
Do not take anti-diarrheal medication without a doctor's approval: In cases of C. diff, stopping diarrhea could worsen the infection by trapping toxins in the colon.
Consider probiotics with caution: If using probiotics, take them at least two hours before or after clarithromycin to ensure the beneficial bacteria are not killed by the antibiotic.
Inform your doctor of a history of antibiotic-associated diarrhea: Past experiences increase the risk of recurrence, and your doctor may choose a different treatment plan.
Seek immediate medical help for severe diarrhea: Call a doctor right away if you experience high fever, severe abdominal pain, or watery/bloody stools.

Can Clarithromycin Cause Diarrhea?

Yes, clarithromycin, like many other antibiotics, can cause diarrhea. This is one of its most commonly reported side effects. The occurrence of diarrhea can range from a mild, temporary inconvenience to a more serious, prolonged condition, such as Clostridioides difficile (C. diff) infection. The risk of developing diarrhea is inherent with antibiotic use because these medications kill not only the harmful bacteria causing an infection but also the beneficial bacteria that maintain a healthy gut microbiome.

The Mechanism Behind Antibiotic-Associated Diarrhea

Clarithromycin belongs to a class of antibiotics called macrolides. These drugs can cause gastrointestinal upset for a couple of reasons. One factor is their effect as a motilin agonist, which stimulates intestinal muscle contractions and can lead to abdominal pain and cramping. More significantly, by disrupting the normal balance of microorganisms in the gut, clarithromycin creates an opportunity for opportunistic bacteria to overgrow. The balance of good and bad bacteria is crucial for healthy digestion, and when this equilibrium is upset, it can lead to diarrhea.

Mild vs. Severe Diarrhea: What to Watch For

Most cases of diarrhea caused by clarithromycin are mild and resolve on their own after the treatment course is completed. These symptoms usually include loose stools and more frequent bowel movements. However, it is critical for patients to be aware of the signs of more severe complications, particularly C. difficile-associated diarrhea (CDAD).

Mild Diarrhea Symptoms

Frequent, but not severe, watery or loose stools.
Often accompanied by mild stomach cramps or abdominal discomfort.
Typically subsides once the antibiotic course is finished.
Doesn't usually require specific treatment beyond supportive care like hydration.

Severe Diarrhea (Potential C. difficile) Symptoms

Severe, persistent, watery diarrhea (sometimes up to 15 times per day).
Bloody or mucus-filled stools.
Severe abdominal cramps and pain.
Fever.
Nausea and loss of appetite.
May occur during or even months after discontinuing the antibiotic.

Comparison Table: Mild Diarrhea vs. C. diff-Associated Diarrhea


Feature	Mild Diarrhea (Common Side Effect)	C. diff-Associated Diarrhea (Severe Complication)
Severity	Generally mild, self-limiting	Can be severe and persistent, potentially fatal
Appearance	Loose, watery stools	Severe, watery, and potentially bloody stools
Frequency	More frequent bowel movements	Very frequent, up to 15 times daily
Onset	Usually during treatment	Can be during or up to 2 months post-treatment
Associated Symptoms	Mild abdominal discomfort, cramping	Severe abdominal cramps, fever, nausea
Management	Hydration, bland diet, observation	Immediate medical consultation, fluid/electrolyte management, specific C. diff treatment

What to Do If Diarrhea Occurs

If you experience mild diarrhea while taking clarithromycin, focus on staying hydrated. Drink plenty of clear fluids like water, broth, or electrolyte-rich drinks to replace lost fluids. Avoid foods that can aggravate diarrhea, such as spicy, fatty, or sugary items. If the upset stomach is bothersome, try taking the medication with food, as advised for some formulations.

If your diarrhea is severe, watery, or bloody, or if it doesn't resolve within a few days after finishing the antibiotic, contact your doctor immediately. Do not take any over-the-counter anti-diarrheal medication without consulting a healthcare professional first, as this can worsen C. difficile infection by trapping toxins in the gut.

Probiotics and Other Preventive Measures

Probiotics are often suggested to help restore the balance of healthy gut flora, potentially reducing the risk of antibiotic-associated diarrhea. If you choose to take a probiotic with clarithromycin, it is crucial to separate the doses by at least two hours. Taking them too close together risks the antibiotic killing the beneficial bacteria in the probiotic supplement. You may also continue taking the probiotic for several weeks after your antibiotic course to help fully restore the gut microbiome.

Patients with a history of antibiotic-associated diarrhea or underlying gastrointestinal conditions should inform their doctor before starting clarithromycin. The NHS even lists prior antibiotic-induced diarrhea as a consideration for who can safely take the medication.

Conclusion

In summary, while clarithromycin can cause diarrhea, most instances are mild and resolve on their own. The key is to monitor your symptoms closely. Mild cases can be managed with adequate hydration and a bland diet, but any signs of severe, persistent, or bloody diarrhea warrant immediate medical attention to rule out a serious condition like C. difficile infection. By understanding the potential for gastrointestinal side effects and knowing when to seek help, patients can navigate their treatment course safely. Always follow your doctor's instructions for the medication, and never hesitate to discuss any side effects you experience. For more information, consult the MedlinePlus drug information page for clarithromycin.

Frequently Asked Questions

Clarithromycin causes diarrhea by disrupting the normal balance of good and bad bacteria in your gut. As a macrolide antibiotic, it kills bacteria indiscriminately, which allows potentially harmful bacteria to flourish and cause inflammation, leading to diarrhea.

You should be concerned and contact your doctor immediately if your diarrhea is severe, persistent, or bloody. Other warning signs include fever, severe abdominal pain, and frequent, watery stools, which could indicate a serious infection like Clostridioides difficile.

You should not take anti-diarrheal medications without consulting your doctor first. For mild antibiotic-associated diarrhea, these medications are generally not necessary. For more severe cases, especially if C. difficile is a concern, they can be dangerous by preventing the body from clearing out the toxins.

Normal antibiotic-associated diarrhea is usually mild, resolves relatively quickly, and is caused by simple gut flora disruption. C. difficile-associated diarrhea is caused by the toxins of the C. diff bacteria, which can overgrow in an imbalanced gut. It is characterized by more severe symptoms, including potentially bloody stools, high fever, and intense cramps, and can occur weeks or months after treatment.

Probiotics may help reduce the risk or severity of antibiotic-associated diarrhea by introducing beneficial bacteria to your gut. However, you must take the probiotic at least two hours apart from the clarithromycin dose to prevent the antibiotic from killing the probiotic bacteria.

It is possible for diarrhea, particularly C. difficile-associated diarrhea, to occur up to two months or more after you finish taking the antibiotic. If this happens, contact your doctor right away for evaluation, as it is a potential sign of a serious infection.

Mild diarrhea from clarithromycin will often resolve on its own within a few days of stopping the medication. Focusing on hydration and a bland diet can aid recovery. However, if symptoms are severe or persist, professional medical evaluation is necessary.