What is the best antibiotic for diarrhea?

October 12, 2025 •

4 min read

Many cases of diarrhea are caused by viruses and are self-limiting, meaning antibiotics are not necessary. However, for specific bacterial infections, determining what is the best antibiotic for diarrhea depends on the pathogen, severity, and local resistance patterns.

Quick Summary

The most effective antibiotic for diarrhea depends on the bacterial cause and symptom severity. Options like Azithromycin, Rifaximin, and Ciprofloxacin are used based on specific conditions, including travelers' diarrhea, dysentery, or infection with certain bacteria.

Key Points

Antibiotics Are Not Always Necessary: Most cases of mild diarrhea are caused by viruses and resolve on their own, making antibiotic treatment unnecessary.
Azithromycin is a Key Option for Severe Diarrhea: It is a preferred treatment for severe travelers' diarrhea, dysentery (bloody stools), and febrile diarrhea.
Fluoroquinolone Resistance is a Growing Concern: Antibiotics like ciprofloxacin are becoming less effective for infectious diarrhea due to increasing bacterial resistance, especially in Campylobacter.
Rifaximin Targets Non-Invasive Infections: This non-absorbed antibiotic is effective for travelers' diarrhea caused by E. coli but is not used for infections involving fever or bloody stool.
Diagnosis is Crucial for Proper Treatment: Identifying the specific bacterial pathogen can guide the most appropriate antibiotic choice and avoid unnecessary prescriptions.
Risk of Antibiotic Resistance: Overuse of antibiotics for diarrhea contributes to bacterial resistance, making future infections harder to treat.

When Are Antibiotics Needed for Diarrhea?

It is a common misconception that all diarrhea requires antibiotic treatment. In reality, most acute cases are caused by viruses and resolve on their own within a few days. Antibiotics are generally reserved for moderate to severe cases, or when a specific bacterial cause is confirmed. A healthcare provider's evaluation is crucial to determine if antibiotic therapy is appropriate. Unnecessary antibiotic use can contribute to the development of antibiotic resistance and may worsen the condition by disrupting beneficial gut bacteria.

Key Indicators for Antibiotic Treatment

Severe Symptoms: Persistent, high-volume, watery diarrhea that is incapacitating or prevents planned activities.
Dysentery: The presence of blood and/or mucus in the stool, often accompanied by fever and severe abdominal cramps.
Fever: A high fever accompanying the diarrhea can indicate a more invasive bacterial infection.
Travelers' Diarrhea: If symptoms are moderate to severe and occur during or after international travel, particularly to high-risk areas.
Specific Pathogens: Confirmed infections with bacteria such as Shigella, Campylobacter, or certain strains of E. coli.
Underlying Conditions: Immunocompromised individuals or those with significant comorbidities may require antibiotics even for less severe illness.

Leading Antibiotics for Diarrhea

Several antibiotics are commonly used for bacterial diarrhea, with the choice depending on the specific circumstances. Each has a different mechanism of action and spectrum of activity.

Azithromycin

Azithromycin, a macrolide antibiotic, is often considered a preferred first-line agent, especially in cases of severe travelers' diarrhea, febrile diarrhea, and dysentery. Its effectiveness extends to a broad range of bacterial pathogens, including Campylobacter species, which have shown increasing resistance to fluoroquinolones. Azithromycin is also considered the treatment of choice for pregnant individuals and children.

Fluoroquinolones (Ciprofloxacin, Levofloxacin)

These antibiotics, such as ciprofloxacin and levofloxacin, have historically been mainstays for treating moderate to severe infectious diarrhea. However, their widespread use has led to increasing rates of resistance in pathogens like Campylobacter and Shigella, particularly in regions of Asia. A single dose may be effective for mild travelers' diarrhea, but a three-day course is often used for more severe cases. Due to resistance concerns, they are now often considered second-line to azithromycin in some areas.

Rifaximin

Rifaximin is a unique, non-systemic antibiotic that is poorly absorbed by the gastrointestinal tract, meaning it primarily acts within the gut. It is specifically indicated for treating travelers' diarrhea caused by non-invasive Escherichia coli. A significant limitation is its ineffectiveness against invasive infections, such as those causing fever or bloody diarrhea (dysentery).

Comparison of Key Diarrhea Antibiotics


Feature	Azithromycin	Ciprofloxacin (Fluoroquinolone)	Rifaximin
Best for	Severe travelers' diarrhea, dysentery, febrile diarrhea, and resistant Campylobacter infections.	Previously widespread, now used cautiously due to resistance. May be used for moderate, non-invasive TD in specific regions.	Non-invasive travelers' diarrhea from E. coli. Also used for IBS-D.
Target Pathogens	Broad spectrum, including Campylobacter, Shigella, and E. coli.	Broad spectrum against enteropathogenic bacteria, but resistance is a growing concern.	Primarily effective against E. coli and other non-invasive bacteria.
Absorption	Systemically absorbed.	Systemically absorbed.	Minimally absorbed, acts mainly within the gut.
Duration	Can be effective as a single dose for watery diarrhea or a 3-day course for dysentery.	A single dose or 3-day course for moderate to severe cases.	Typically a 3-day course.
Contraindications	Use with caution in patients with heart issues.	Not recommended for children, pregnant women, or areas with high resistance. Can cause tendinitis.	Ineffective for bloody diarrhea or fever.

The Role of Diagnosis and Resistance

Proper diagnosis is critical for effective treatment. A stool culture can identify the specific pathogen and its antibiotic susceptibility, guiding the best choice of medication. Without a confirmed diagnosis, doctors must use an empirical approach based on the patient's symptoms and travel history. This approach is particularly important with the rise of antibiotic resistance. For example, high rates of fluoroquinolone-resistant Campylobacter in certain parts of the world, like Thailand, make azithromycin the preferred empirical choice.

Conclusion

There is no single "best" antibiotic for diarrhea, as the most effective treatment is determined by the cause and severity of the illness. Mild, non-bacterial cases generally do not require antibiotics and are best managed with supportive care, including hydration. For moderate to severe bacterial diarrhea, especially with dysentery or fever, azithromycin is a common and effective choice, particularly in regions with high fluoroquinolone resistance. Rifaximin offers a targeted option for non-invasive travelers' diarrhea caused by E. coli. All antibiotic treatments for diarrhea should be prescribed by a healthcare provider after a thorough evaluation to ensure safety and effectiveness while mitigating the risks of antibiotic resistance.

You can learn more about managing travelers' diarrhea from the CDC.

Frequently Asked Questions

No, it is not recommended to self-prescribe antibiotics. The correct antibiotic depends on the cause, which requires a medical diagnosis. Inappropriate antibiotic use can lead to adverse effects and contribute to antibiotic resistance.

You should see a doctor if you experience severe symptoms, such as high fever, bloody stool (dysentery), severe abdominal pain, signs of dehydration, or if diarrhea persists beyond a few days.

For severe travelers' diarrhea, Azithromycin is often the preferred antibiotic, especially in regions with high fluoroquinolone resistance. For moderate, non-invasive diarrhea, Rifaximin or fluoroquinolones may also be used, depending on the travel location and risk factors.

Loperamide can be used for mild to moderate watery diarrhea. However, it should generally be avoided if you have dysentery (bloody diarrhea) or fever, as it could worsen the condition.

Azithromycin is effective against a broad range of invasive bacteria, including Shigella and Campylobacter, which are common causes of dysentery. It is also effective in areas where other antibiotics, like fluoroquinolones, face high resistance.

Rifaximin is a non-systemic antibiotic, meaning it stays primarily in the gastrointestinal tract and is minimally absorbed into the bloodstream. It is only effective for non-invasive infections, whereas other antibiotics like Azithromycin are absorbed systemically and can treat more severe, invasive infections.

For pregnant women and children, Azithromycin is the preferred antibiotic for travelers' diarrhea due to its safety profile. Any antibiotic use during pregnancy should be carefully managed by a healthcare provider.