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Home » Can UTI Cause Loose Stool or Diarrhea? 4 Facts

Can UTI Cause Loose Stool or Diarrhea? 4 Facts

Can UTI Cause Loose Stool or Diarrhea? 4 Facts

Our content is not intended nor recommended as a substitute for medical advice by your doctor. Use for informational purposes only.

UTI does not usually cause loose stools or diarrhea. However, diarrhea and loose stools can result from the antibiotics used for UTI treatment.

Here are the top six UTI facts about its relationship to bowel movements (diarrhea and loose stools):

  • Diarrhea is not a typical symptom of UTI.
  • UTI treatment (antibiotics) may lead to diarrhea or loose stool.
  • A complicated UTI (sepsis) may cause diarrhea or loose stool.
  • Having UTI and loose stool simultaneously doesn’t always mean one caused the other (correlation doesn’t mean causation).
  • Think of stress, food intolerances, IBS, and other common causes of diarrhea.
  • A fistula (abnormal connection) between the urinary bladder and the rectum, colon, or small intestine is a rare cause of UTI and diarrhea.

1. Diarrhea is not a typical symptom of UTI.

Urinary tract infections (UTIs) are very common (especially in females). About 90% of UTIs lead to acute cystitis (urinary bladder inflammation).

However, a minority of people may get a more severe (complicated) form of UTI where the infection spreads to the kidneys or the bloodstream.

The symptoms are often more severe in complicated UTIs, and the digestive system may become involved in diarrhea or loose stools.

Diarrhea or loose stool is not reported as a frequent symptom of UTI.

Uncomplicated UTI symptoms:

  • Dysuria (pain or burning when you pee).
  • Frequent desire to pee but only a small amount of urine comes out.
  • Sudden urge to pee.
  • Frequent waking up to pee at night (nocturia).
  • Bladder pain (in the lower abdomen and/or the lower back).
  • Bloody (reddish or pink) urine or small blood clots in urine (sometimes).
  • Cloudy (turbid) urine.
  • NO high fever.
  • NO Flank pain.
  • NO chills.
  • NO diarrhea or loose stool.

2. UTI treatments can cause loose stool or diarrhea.

The main treatment for UTI is antibiotics. Antibiotics are given either empirically or according to the urine culture results.

Common antibiotics used for UTIs are:

  • Penicillins such as Amoxicillin/clavulenate.
  • Cephalosporins, such as ceftriaxone.
  • Quinolones such as ciprofloxacilin.
  • Nitrofurantoin.
  • Sulfa drugs, such as Sulfamethoxazole/trimethoprim.

Also, Patients with UTI may receive other treatments for UTI, such as nonsteroidal anti-inflammatory drugs (NSAIDs), which can also cause diarrhea.

These medications may cause loose stool or diarrhea by different mechanisms (direct irritant effects, affection of the intestinal microbiota, etc.).

Most cases of drug-induced diarrhea or loose stool are mild and self-limiting. A landmark feature of diarrhea due to medication is that the onset is AFTER initiating UTI medications.

The presence of diarrhea before you start antibiotics or take any medication excludes medications as a cause of bowel habit changes.

A special notice about antibiotic-associated diarrhea:

Most cases of antibiotic-associated diarrhea are mild and short in duration (loose stool rarely causes watery diarrhea).

However, antibiotics may cause a serious colon infection with ulcers and bloody stools due to clostridium difficile infection (CDI).

It is manifested by sudden onset diarrhea, blood and mucus in stool, severe abdominal cramps (often diffuse), and fever.

Consult your doctor immediately if you have bloody diarrhea and fever after initiating antibiotic treatments for UTI.

Learn More about C. difficile diarrhea characteristics.

3. A complicated UTI may cause loose stool or diarrhea.

The term “Complicated UTI” refers to the spread of the infection beyond the urinary bladder. When the bacteria reach the kidneys or the bloodstream, other symptoms occur, including:

  • All the classic symptoms of acute cystitis (dysuria, urgency, frequency, blood in urine, etc.).
  • Fever >37.7°C (>99.9°F).
  • Chills or rigors.
  • Significant fatigue, muscle aches, or any other feature of systemic illness.
  • Flank pain.
  • Pelvic or perineal pain in men.
  • Tenderness over the kidney area when your doctor examines it (A tender costovertebral angle at the upper back just below the ribs).
  • Digestive symptoms such as Nausea, vomiting, loose stool, or diarrhea.

So, The presence of fever, flank pain, loose stool, or diarrhea may indicate the presence of a complicated UTI.

However, diarrhea or loose stool alone (flank pain and high fever) doesn’t signify a complicated UTI.

In such a case, think of other causes of loose stool or diarrhea with UTI, such as drugs, dietary changes, or gut infections.

4. Correlation doesn’t always mean causation.

Time coincidence is another explanation for diarrhea and loose stool with UTI. Diarrhea and UTI can happen simultaneously; each occurs due to a separate cause (time is the only connection).

Both UTI and diarrhea (or loose stool) are common conditions. Even recurrent diarrhea and UTI are common (especially in females).

Common causes of diarrhea that may co-exist with UTI include:

A. Acute diarrhea:

  • Infection (viral, bacterial, or protozoal) leading to diarrhea (gastroenteritis).
  • An attack of food intolerance or allergy (such as ingesting a considerable.
  • Food poisoning (food-borne diarrheal illness).
  • An attack of stress or anxiety.
  • Recent intake of medication that leads to diarrhea (whether for UTI or any other condition).

B. Chronic or recurrent diarrhea.

  • Food intolerances such as lactose intolerance.
  • IBS with predominant diarrhea.
  • Chronic gut infections.
  • Celiac disease.
  • Inflammatory bowel disease.
  • Post-cholecystectomy diarrhea.
  • Diabetes mellitus.
  • SIBO.
  • Hyperthyroidism, and others.

5. Versico-rectal or colovesical fistulas are very rare causes of diarrhea with UTI.

A fistula is an abnormal connection between two hollow organs through a tube-like tract.

Abnormal connections between the urinary bladder and the adjacent colon or rectum are called colovesical and vesicorectal fistulas. Also, the fistula can form between the urinary bladder and the small intestine (vesicoenteric fistula).

Common causes include:

  • Diverticulitis (the most common cause).
  • Colorectal cancer.
  • Crohn’s disease.
  • Atypical infections such as T.B.
  • Pelvic radiotherapy.
  • Trauma.

Patients with these types of fistula often have a co-morbid intestinal disease or major infections such as T.B. These fistulas don’t affect healthy ones.

The fistula leads to the passage of colon bacteria (and stool) to the urinary bladder leading to severe forms of urinary tract infections.

The fistula may also lead to a passage of urine to the colon or the rectum leading to loose stool or diarrhea.

Learn More.

6. When to see a doctor for diarrhea with UTI:

If you have diarrhea or loose stool with UTI, see a doctor if you have:

  • Severe (frequent) watery diarrhea that doesn’t improve.
  • Bloody or blackish stool.
  • High-grade fever.
  • Severe abdominal cramps.
  • Severe flank pain.
  • Severe nausea or vomiting.
  • Bloody diarrhea after taking antibiotics for UTI treatment (suspicion of C. difficile colitis).


  • Evidence-based
  • Written by a doctor.

MD, Internal Medicine and Nephrology specialist.
Dr. Esraa A. Magid
Dr. Esraa A. MagidAuthor