Can Fluoxetine Cause UTI? Understanding the Indirect Link

October 14, 2025 •

3 min read

While antibiotics are the standard treatment for urinary tract infections (UTIs), a number of medications, including certain antidepressants, can inadvertently increase your risk. For fluoxetine, a selective serotonin reuptake inhibitor (SSRI), this link is not direct but stems from a rare side effect that can create a breeding ground for bacteria.

Quick Summary

Fluoxetine can contribute to an increased risk of urinary tract infections by causing urinary retention, a rare side effect. This condition prevents complete bladder emptying, allowing bacteria to multiply and potentially cause a UTI.

Key Points

Indirect Link: Fluoxetine can cause urinary retention, which then increases the risk of a UTI by allowing bacteria to multiply in the bladder.
Serotonin's Role: The effect on the urinary system is caused by fluoxetine's impact on serotonin receptors, which are involved in regulating bladder function.
Recognize Symptoms: Look for signs of urinary retention like painful urination (dysuria), difficulty starting urination, or feeling that the bladder is not empty.
Rare Side Effect: While a documented adverse event, urinary retention is considered an uncommon side effect of fluoxetine.
Mitigate Risk: Management involves consulting a doctor for potential dosage adjustments, maintaining hydration, practicing timed voiding, and discussing alternative medications if necessary.
Consult a Doctor: Never stop taking fluoxetine suddenly due to urinary symptoms; a healthcare provider can provide guidance and adjust treatment safely.

The Indirect Pathway: Fluoxetine and UTI Risk

Fluoxetine, an SSRI, does not directly cause UTIs. The connection is indirect and involves a rare side effect called urinary retention. Urinary retention is the inability to fully empty the bladder, leading to stagnant urine, which can promote bacterial growth and increase the risk of infection.

The Role of Serotonin in Bladder Function

Fluoxetine works by increasing serotonin levels, affecting receptors found in the bladder and urinary tract. This can interfere with normal urination signals, potentially leading to increased sympathetic activity and inhibited parasympathetic function. This imbalance can cause bladder muscles to relax or sphincter muscles to tighten, preventing complete voiding and increasing the risk of bacterial overgrowth.

Incidence and Risk Factors

Urinary retention is a rare side effect of fluoxetine, observed in both adults and adolescents. Adverse event reports indicate a small percentage of SSRI users experience urinary retention. Certain groups, such as the elderly, pregnant individuals, and postpartum women, may have a higher risk. Taking fluoxetine with other medications affecting bladder function, like anticholinergics, can also increase the risk.

Symptoms and Recognition

Recognizing urinary retention symptoms is important for preventing UTIs. Symptoms can range from incomplete emptying to acute retention requiring immediate medical care. For more details on the common signs of fluoxetine-induced urinary issues, you can refer to {Link: DrOracle.ai https://www.droracle.ai/articles/29314/are-there-any-urinary-side-effects-with-prozac-and-wellbutrin}. Report any changes in urinary habits to your doctor, especially after starting fluoxetine.

Comparison of Urinary Side Effects: Fluoxetine vs. Other Agents

The table below compares the urinary effects of fluoxetine with other medications known to cause urinary problems. For the full table, including detailed mechanisms and typical side effects, see {Link: DrOracle.ai https://www.droracle.ai/articles/29314/are-there-any-urinary-side-effects-with-prozac-and-wellbutrin}.


Feature	Fluoxetine (SSRI)	Tricyclic Antidepressants (TCAs)	SGLT2 Inhibitors	Anticholinergic Drugs	Opioids
Mechanism	Affects serotonin receptors in the bladder, potentially leading to retention.	Block muscarinic receptors, directly impairing bladder contraction.	Increase glucose in urine, promoting bacterial growth.	Block acetylcholine, reducing bladder muscle contraction.	Act on opioid receptors and have anticholinergic effects, causing retention.
Effect on Bladder	Can increase sphincter tone and decrease contractility, causing retention.	Impair bladder contraction, leading to incomplete emptying.	Primarily increase urinary glucose, aiding bacterial growth.	Inhibit bladder contraction, causing significant retention.	Reduce bladder fullness sensation and decrease contraction.
Typical Side Effect	Infrequent urinary retention, frequent urination, dysuria.	Known side effect due to strong anticholinergic properties.	Increased UTI frequency is common.	Urinary retention is a primary side effect.	Urinary retention is a common side effect.

Management and Prevention

Managing fluoxetine-related urinary issues requires discussing symptoms with a healthcare provider. Do not stop fluoxetine abruptly, as this can cause withdrawal. Strategies may include dosage adjustment, maintaining hydration, timed voiding, and medication timing. Monitoring urinary symptoms is important, and in severe cases, a doctor might suggest an alternative antidepressant. For an example of a case involving fluoxetine-related urinary retention in an adolescent, refer to {Link: PMC NCBI https://pmc.ncbi.nlm.nih.gov/articles/PMC9466638/}.

Conclusion

Fluoxetine's link to increased UTI risk is indirect, primarily through causing urinary retention due to its effects on serotonin receptors in the urinary system. Recognizing symptoms and consulting a healthcare provider are crucial for management, which may involve dosage changes, hydration, or considering alternative treatments. Close communication with a doctor is essential for patient safety.

Frequently Asked Questions

No, fluoxetine does not directly cause a UTI. Instead, it can cause urinary retention—the inability to fully empty the bladder—which creates an environment where bacteria can multiply, increasing the risk of an infection.

Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), influences serotonin levels in the body, including receptors in the bladder and urinary tract. This can alter the nerve signals that control urination, potentially leading to incomplete bladder emptying.

Urinary retention is a rare but documented side effect of fluoxetine use. While some data on SSRIs as a class exists, case reports confirm the phenomenon, indicating that it is not a frequent occurrence.

Signs include difficulty initiating urination, a weak stream, feeling that the bladder is not completely empty after voiding, and painful urination (dysuria). If you experience these symptoms, contact your healthcare provider.

Elderly individuals, pregnant or postpartum women, and those taking other medications that affect bladder function (like anticholinergics) may be at an increased risk.

If you experience any urinary symptoms, you should contact your doctor immediately. Do not stop taking fluoxetine on your own. Your doctor can evaluate your condition and recommend a dosage adjustment or an alternative medication.

Yes, proper management is key. By addressing the urinary retention through strategies like dosage adjustments, staying hydrated, and timed voiding, you can reduce the risk of stagnant urine and prevent a UTI from developing.