A urinary tract infection can cause blood in your urine, and in more severe cases, it can produce visible blood clots. The medical term for blood in urine is hematuria, and infections are one of the most common reasons it happens. Most people with a straightforward UTI notice only a pinkish tinge or slightly reddish urine, but when the infection is aggressive enough to damage the bladder lining more deeply, clots can form and become visible in the toilet bowl. The sight is understandably alarming, but the underlying cause is usually treatable once identified.
How a UTI Causes Bleeding in the Bladder
The bladder is lined with a thin layer of tissue that acts as a barrier between urine and the underlying blood vessels. During a UTI, bacteria invade this lining and trigger inflammation. The body’s immune response sends white blood cells to the area, and the resulting swelling and tissue irritation can erode small blood vessels near the surface. When those vessels break open, blood leaks into the urine. In mild infections, only a microscopic amount of blood escapes, detectable by a urine test strip but invisible to the naked eye. In more severe infections, enough bleeding occurs that you can see the discoloration clearly.
When the damage goes deeper, the condition is sometimes called hemorrhagic cystitis. This involves actual necrosis of the bladder’s lining and its associated blood vessels, producing heavier bleeding that can include clots.1Research and Reports in Urology. Uncommon Haemorrhagic Cystitis of Infectious Origin: A Narrative Review for Urologists While hemorrhagic cystitis is more commonly associated with chemotherapy drugs, radiation treatment, and chemical exposure, bacterial and viral infections can also cause it. The severity ranges from mild pink-tinged urine all the way to heavy bleeding with large clots that can actually block urine flow.
Visible Clots Versus Pink-Tinged Urine
There is an important distinction between seeing a slight color change in your urine and passing actual clots. Pink or tea-colored urine during a UTI is relatively common and usually resolves once antibiotics clear the infection. This type of bleeding is superficial, originating from irritated but intact tissue. It looks concerning but typically does not indicate serious structural damage.
Visible blood clots are a different story. Clots form when enough blood accumulates in the bladder that the body’s clotting mechanisms activate right there in the urine. You might see dark red or brownish lumps, stringy material, or tissue-like fragments. Clots are less common in routine UTIs and tend to signal either a more aggressive infection, an underlying condition that makes bleeding worse, or a cause other than a simple UTI. If you are passing clots, it is worth getting evaluated promptly rather than assuming the infection alone explains it.
Who Is More Likely to See Blood or Clots
Certain groups face a higher risk of UTI-related hematuria progressing to visible clots. Understanding these risk factors helps explain why two people with the same type of infection can have very different experiences.
Postmenopausal women are particularly vulnerable. Lower estrogen levels after menopause lead to changes in the urinary tract and vaginal tissue, including dryness, thinning of the mucosal lining, and increased fragility of those tissues.2PubMed Central. Urinary tract infections after menopause A thinner, more fragile bladder lining bleeds more easily when bacteria irritate it, so postmenopausal women may see blood or clots from infections that would produce no visible bleeding in younger women.
In men, benign prostatic hyperplasia (an enlarged prostate) is a recognized risk factor. The enlarged prostate can obstruct urine flow, create conditions that promote infection, and independently cause hematuria. When a UTI occurs on top of an already enlarged prostate, the combination can lead to more pronounced bleeding.3PubMed Central. Management of the complications of BPH/BOO Hematuria, urinary tract infection, and urinary retention are all listed among the recognized complications of prostatic obstruction, and they often overlap.
Children can also develop bloody urine from UTIs. Infection is considered a frequent cause of both visible and microscopic hematuria in pediatric patients.4Pediatric Clinics of North America. Gross Hematuria in Children In young children who cannot describe their symptoms well, bloody urine is sometimes the first clue that an infection is present. Clots are less common in children with simple UTIs, but any visible blood in a child’s urine warrants medical attention to rule out other causes.
Urinary Catheters, Clots, and Infection
People with indwelling urinary catheters face a uniquely high risk of both UTIs and blood clots in their urine. The catheter itself causes mechanical irritation and minor tissue damage to the bladder wall. This triggers the body’s wound-healing response, including the deposition of fibrinogen and fibrin, the proteins that form the structural backbone of blood clots. Research in animal models has shown that catheterization provokes local tissue damage that activates coagulation and converts fibrinogen into fibrin right inside the bladder.5Nature Communications. Fibrinolytic-deficiencies predispose hosts to septicemia from a catheter-associated UTI
This creates a vicious cycle. The fibrin deposited in the bladder as part of the healing response also provides a surface that bacteria exploit to build biofilms and establish infection. Catheter-associated UTIs are among the most common hospital-acquired infections, and the combination of mechanical irritation, fibrin deposition, and bacterial colonization can lead to significant hematuria with clot formation. For catheterized patients, clots can be especially problematic because they may block the catheter itself, obstructing urine drainage and creating a medical emergency.
What to Do When You See Clots
If you notice blood clots in your urine during a suspected UTI, the right move depends on the severity. A single small clot alongside typical UTI symptoms like burning, urgency, and frequency is worth mentioning to your doctor but does not usually require an emergency visit. Persistent or worsening clots, difficulty urinating, significant pain, or lightheadedness from blood loss are reasons to seek urgent care.
For severe hemorrhagic cystitis with active clot formation, treatment follows a specific escalation. The first priority is making sure the patient is hemodynamically stable, meaning their blood pressure and heart rate are not dangerously affected by blood loss. Conservative management starts with establishing bladder drainage, manually evacuating clots, and running continuous bladder irrigation through a large catheter to prevent new clots from accumulating and blocking urine flow.6PubMed Central. Hemorrhagic Cystitis: Making Rapid and Shrewd Clinical and Surgical Decisions for Improving Patient Outcomes If the bleeding persists despite irrigation, doctors may need to perform a cystoscopy to look inside the bladder, evacuate clots directly, and potentially cauterize bleeding vessels.
For most UTI-related hematuria that does not involve large or persistent clots, the blood typically clears within a few days of starting appropriate antibiotics. Drinking plenty of fluids helps dilute the urine and flush the bladder, which can reduce irritation and help move small clots along before they grow larger.
UTIs and Blood Clots Elsewhere in Your Body
There is a separate and less widely known connection between UTIs and blood clots that form in the veins of your legs or lungs, known as deep vein thrombosis and pulmonary embolism. This is a systemic effect of infection, not a local bladder phenomenon, and it catches many people off guard because it seems unrelated to a urinary problem.
A large community-based study found that the risk of deep vein thrombosis roughly doubled in the weeks following a UTI, with an incidence ratio of about 2.1. The risk of pulmonary embolism was similarly elevated, also around 2.1 times the baseline risk. The danger was highest in the first two weeks after infection and gradually returned to normal over the following year.7PubMed. Risk of deep vein thrombosis and pulmonary embolism after acute infection in a community setting The mechanism likely involves the systemic inflammatory response to infection, which activates clotting factors throughout the bloodstream, not just at the site of the UTI.
A separate study looked at antibiotic prescriptions as a proxy for acute infections and found an even more striking association. During periods of antibiotic treatment, the risk of a first venous blood clot was about five times higher than at baseline. The risk of a recurrent clot was about double.8PubMed. Antibiotic use as a marker of acute infection and risk of first and recurrent venous thrombosis The researchers concluded that acute infections should be considered a provoking risk factor for venous thrombosis, similar to how surgery or prolonged immobility are recognized triggers.
This does not mean that every person with a UTI needs to worry about a leg clot or a pulmonary embolism. The absolute risk remains low for most healthy people. But if you have other risk factors for blood clots, such as recent surgery, use of hormonal contraceptives, a personal or family history of clotting disorders, or prolonged bed rest, a UTI layered on top of those factors could meaningfully raise your overall risk. Symptoms to watch for include leg swelling, calf pain, unexplained shortness of breath, or chest pain in the weeks after an infection.
When Hematuria Is Not Actually From the UTI
One of the most important things to understand about blood in your urine is that a UTI is only one of many possible causes. Kidney stones, vigorous exercise, certain medications like blood thinners, and even some foods can produce red or pink urine. More seriously, bladder cancer and kidney cancer can present with painless hematuria that looks identical to what a UTI might produce.
The overlap between UTI symptoms and other conditions is a real clinical challenge. A UTI and bladder cancer can both cause blood in the urine, urgency, and frequency. If a doctor treats the UTI and the blood goes away, the infection was likely the sole cause. But if blood persists after the infection has cleared, further investigation is warranted. Guidelines recommend that patients with persistent hematuria or infections caused by bacteria other than the usual culprit, E. coli, should undergo cystoscopy and imaging of the upper urinary tract to rule out other pathology.9Journal of Obstetrics and Gynaecology Canada. Recurrent Urinary Tract Infection
This is particularly relevant for people over 50 and for anyone who smokes or has a history of smoking, since these are the groups at highest risk for urinary tract cancers. It is also worth noting that recurrent UTIs themselves can sometimes be a symptom of an underlying structural problem, such as a bladder diverticulum or a kidney abnormality, that independently contributes to bleeding. The takeaway is straightforward: blood that clears with antibiotic treatment is reassuring, while blood that keeps coming back deserves a closer look.
Why Some Infections Cause More Bleeding Than Others
Not all UTIs are created equal when it comes to hematuria. The strain of bacteria, the depth of tissue invasion, and the health of the bladder lining all influence how much bleeding occurs. Most uncomplicated UTIs are caused by E. coli strains that attach to the surface of the bladder lining and cause superficial inflammation. These infections often produce little or no visible blood.
More invasive bacteria, or infections in people with compromised bladder defenses, can penetrate deeper into the tissue. Hemorrhagic cystitis of infectious origin can be caused by a range of pathogens beyond the usual bacteria, including certain viruses (particularly adenoviruses and the BK virus in immunocompromised patients), fungi, and even parasites.1Research and Reports in Urology. Uncommon Haemorrhagic Cystitis of Infectious Origin: A Narrative Review for Urologists These less common causes tend to be harder to diagnose and more likely to produce significant bleeding with clots, partly because they are not always suspected early and partly because they may not respond to standard antibiotic therapy.
Immunosuppressed individuals, including organ transplant recipients and people undergoing chemotherapy, are the group most likely to encounter viral hemorrhagic cystitis. For these patients, bloody urine with clots can be a recurring and difficult problem that requires specialized management well beyond a simple course of antibiotics.
Medications That Can Worsen UTI-Related Bleeding
If you are taking blood-thinning medications such as warfarin, direct oral anticoagulants, or even daily aspirin, a UTI that would normally produce minimal bleeding can lead to much more dramatic hematuria. Anticoagulants do not cause UTIs or bladder inflammation, but they impair the body’s ability to form clots at the site of damaged tissue. The same small blood vessel rupture that would seal itself quickly in someone not on blood thinners can continue oozing in someone who is.
This creates a clinical dilemma. Stopping the anticoagulant to control bladder bleeding can expose the patient to the risk of stroke or heart attack, depending on why they were prescribed the medication in the first place. Continuing the medication can worsen the hematuria. Doctors typically try to manage the bleeding without stopping anticoagulation, using hydration and sometimes bladder irrigation, and only adjust the blood thinner if the bleeding becomes life-threatening. If you are on anticoagulants and develop a UTI with visible blood, let your prescribing doctor know so they can monitor the situation.
Hydration, Cranberry, and Other Home Measures
For mild UTI-related hematuria without significant clots, the most useful thing you can do at home is drink plenty of water. High fluid intake dilutes the urine, which reduces irritation to the inflamed bladder lining and helps flush bacteria and small clots out before they can grow. Concentrated, dark urine sitting in an inflamed bladder is the worst-case scenario for both comfort and clot formation.
Cranberry products are frequently mentioned in the context of UTI prevention, and while there is some evidence they may reduce the frequency of recurrent UTIs in certain populations, they do not treat active infections and have no direct effect on hematuria. If you are already bleeding, cranberry juice is not going to stop it. What you need is appropriate antibiotic treatment and, if the bleeding is heavy, medical evaluation.
Over-the-counter urinary analgesics containing phenazopyridine can help with the pain and burning of a UTI but will turn your urine bright orange, which can make it harder to assess whether you are still bleeding. If your doctor has asked you to monitor the color of your urine, mention that you are taking phenazopyridine so they can factor that in.
Avoiding caffeine, alcohol, and spicy foods during an active UTI is reasonable, as these can all increase bladder irritation. None of these dietary changes will stop hematuria on their own, but reducing additional irritation to an already inflamed bladder can make the recovery period less uncomfortable and may reduce the chance of minor bleeding worsening.