Can UTI medication cause diarrhea?

October 12, 2025 •

4 min read

According to the Cleveland Clinic, diarrhea is a common side effect of antibiotics, and a significant percentage of people experience this while taking medication for an infection. This is especially true for urinary tract infections (UTIs), where the prescribed medication often leads to this uncomfortable side effect.

Quick Summary

Yes, antibiotic medication for UTIs can cause diarrhea by disrupting the normal balance of gut bacteria. The risk varies by antibiotic type, with some broad-spectrum drugs more likely to cause this side effect. Management strategies include probiotics, dietary changes, and staying hydrated. Severe or persistent diarrhea may signal a serious infection and requires medical attention.

Key Points

Antibiotics are the primary cause: Antibiotics used for UTIs can cause diarrhea by killing off the beneficial bacteria in your gut along with the harmful ones.
Risk varies by medication: The likelihood of experiencing diarrhea depends on the specific antibiotic, with broad-spectrum antibiotics generally posing a higher risk.
Most cases are mild: For most individuals, antibiotic-associated diarrhea is temporary and resolves on its own shortly after the treatment course ends.
Probiotics can help: Taking a probiotic supplement or consuming probiotic-rich foods like yogurt can help restore gut bacteria and prevent or manage diarrhea.
Stay hydrated and eat bland foods: The BRAT diet (bananas, rice, applesauce, toast) and consuming electrolyte-rich fluids can help manage symptoms and prevent dehydration.
Finish the prescription: Do not stop taking your medication early, even if you feel better, as this can lead to a return of the infection and antibiotic resistance.
Watch for severe symptoms: Severe, watery, or bloody diarrhea accompanied by fever and cramping could indicate a serious C. diff infection, which requires immediate medical attention.

Why UTI Medications Can Cause Diarrhea

Diarrhea is a frequent and unpleasant side effect for many people undergoing antibiotic treatment for a urinary tract infection. The primary reason for this lies in the way antibiotics function. While these powerful medications are designed to kill the harmful bacteria causing the infection, they are not selective and also eliminate many of the beneficial bacteria residing in your gut.

This disruption, known as dysbiosis, upsets the delicate balance of your intestinal flora, leading to digestive issues. When the 'good' bacteria that help with digestion and protect against pathogenic overgrowth are depleted, it can affect your body's ability to process waste, resulting in loose, watery stools. The severity of the diarrhea can depend on several factors, including the type of antibiotic used, the duration of the treatment, and individual risk factors. In most cases, the diarrhea is mild and resolves shortly after completing the medication course.

Specific UTI Antibiotics Linked to Diarrhea

Several different types of antibiotics are commonly prescribed for UTIs, and they have varying likelihoods of causing diarrhea. Broad-spectrum antibiotics, which target a wide range of bacteria, are generally associated with a higher risk of gastrointestinal side effects.

Amoxicillin-Clavulanate (Augmentin): Used for some UTIs, Augmentin is known to cause a relatively high incidence of diarrhea compared to amoxicillin alone.
Sulfonamides (e.g., Trimethoprim-sulfamethoxazole or Bactrim): These are a common first-line treatment for UTIs. Diarrhea is a recognized side effect, as these drugs can disrupt gut flora.
Nitrofurantoin (Macrobid, Macrodantin): While generally having a lower systemic impact than some broad-spectrum options, nitrofurantoin can still cause gastrointestinal side effects, including diarrhea, nausea, and stomach upset. Taking it with food is often recommended to minimize these issues.
Fluoroquinolones (e.g., Ciprofloxacin or Cipro): Though their use for uncomplicated UTIs is now discouraged due to safety concerns and resistance, fluoroquinolones are still used for more complex infections. They are associated with a significant risk of antibiotic-associated diarrhea.
Phenazopyridine (AZO, Pyridium): This medication is a non-antibiotic pain reliever for UTI symptoms. While it doesn't treat the infection, it can also cause digestive upset and diarrhea in some individuals.

A Serious Complication: Clostridioides difficile (C. diff)

While mild diarrhea is typically a temporary inconvenience, it is crucial to be aware of the signs of a more serious condition known as Clostridioides difficile (C. diff) infection. This bacteria can flourish when the normal gut flora is wiped out by antibiotics, leading to severe inflammation of the colon (colitis).

Symptoms of a C. diff infection include:

Severe, watery diarrhea (often three or more watery stools per day)
Abdominal pain and cramping
Fever
Loss of appetite
Blood or pus in the stool

C. diff infection can occur during antibiotic treatment or weeks to months after stopping the medication. If you experience any of these symptoms, you must contact your healthcare provider immediately. Stopping the antibiotic on your own is not the correct course of action, and treating the diarrhea with over-the-counter medication without a doctor's consultation could worsen the situation.

How to Manage and Prevent Diarrhea from UTI Medication

Managing antibiotic-associated diarrhea involves a combination of dietary adjustments and supportive measures. Taking proactive steps can help minimize discomfort and maintain your gut health throughout the treatment period.

Here are some key strategies:

Take Probiotics: Consider taking a probiotic supplement, such as Lactobacillus rhamnosus GG or Saccharomyces boulardii, which can help replenish the beneficial bacteria in your gut. It's best to take the probiotic a few hours away from your antibiotic dose to maximize its effectiveness.
Eat Probiotic-Rich Foods: Incorporate fermented foods like yogurt with live active cultures, kefir, and sauerkraut into your diet.
Adjust Your Diet: The BRAT diet (bananas, rice, applesauce, and toast) consists of bland, easy-to-digest foods that can help solidify stools. Avoiding spicy, greasy, or high-fat foods, caffeine, and alcohol is also recommended.
Stay Hydrated: Diarrhea can cause dehydration, so it's vital to drink plenty of fluids. Electrolyte-rich drinks, such as sports drinks or broth, are more effective than plain water at replenishing lost minerals.
Take Medication with Food: For many antibiotics, taking the dose with food can help reduce stomach upset. Always follow your doctor's specific instructions, as some antibiotics should be taken on an empty stomach.

Common UTI Antibiotics and Diarrhea Risk


Antibiotic Class	Common Examples	Diarrhea Risk Level	Why it Causes Diarrhea	Take With Food?
Penicillins	Amoxicillin, Augmentin	Medium to High (esp. Augmentin)	Broad-spectrum, disrupts gut flora	Yes, to reduce stomach upset
Sulfonamides	Bactrim	Medium	Disrupts gut flora	Yes, often recommended
Nitrofurantoin	Macrobid, Macrodantin	Low to Medium	Localized GI effects	Yes, to reduce GI issues
Fluoroquinolones	Ciprofloxacin, Levofloxacin	High	Broad-spectrum, can promote C. diff overgrowth	Yes, unless specified

Conclusion

Experiencing diarrhea while taking UTI medication is a common side effect, primarily due to the antibiotic's effect on gut bacteria. While often mild and temporary, it's essential to manage it with dietary changes, hydration, and potentially probiotics. Monitoring symptoms for any signs of a severe C. diff infection is also crucial. Never stop taking your prescribed medication without consulting your healthcare provider, and always finish the full course to ensure the infection is completely cleared. By understanding the cause and implementing effective management strategies, you can minimize the discomfort and focus on your recovery. For specific medical advice, always consult your doctor. For further information on managing medication side effects, a valuable resource is the Cleveland Clinic.

Frequently Asked Questions

Mild antibiotic-associated diarrhea typically subsides within a few days of finishing the full course of your UTI medication. If it persists or worsens, especially with severe symptoms, contact your doctor.

You should not take over-the-counter anti-diarrheal medication without consulting your doctor. In cases of a serious C. diff infection, these medications could make the condition worse by trapping the toxins in your colon.

Studies suggest that specific probiotic strains like Lactobacillus rhamnosus GG and Saccharomyces boulardii are effective for preventing antibiotic-associated diarrhea. Look for these strains in supplements or fermented foods.

To maximize effectiveness, it is recommended to take your probiotic at least a few hours apart from your antibiotic dose. This prevents the antibiotic from immediately killing the beneficial bacteria in the supplement.

For many UTI antibiotics, taking the medication with food can help reduce stomach upset and nausea. However, always follow the specific instructions provided by your doctor or pharmacist, as some medications are best taken on an empty stomach.

It is best to avoid spicy, greasy, high-fiber, and fatty foods. Limiting caffeine and alcohol can also help, as these can irritate the digestive system and worsen diarrhea.

Yes, while not an antibiotic, phenazopyridine is a pain reliever for UTI symptoms and lists diarrhea as a possible side effect. If you experience this, it may be a reaction to the medication.