Passing blood clots in your urine is your body signaling that something is bleeding somewhere along the urinary tract, from the kidneys down to the urethra. In men, the most common culprits are an enlarged prostate, urinary tract infections, bladder or kidney stones, and, less commonly, cancers of the bladder or kidney. The presence of actual clots, rather than just a pink tinge, generally means the bleeding is brisk enough that blood is pooling and coagulating before you pass it. That warrants medical attention, not a wait-and-see approach.
What Clots Actually Tell You
Visible blood in the urine, called gross hematuria, covers a wide spectrum. Urine can look faintly pink, dark tea-colored, or frankly red with solid clots. When clots form, it means enough blood has accumulated in the bladder to start clotting before you urinate. Clots can be small and stringy or large enough to partially block the flow of urine, causing pain and a feeling of incomplete emptying. In hospital settings, large clots sometimes require catheter irrigation to flush them out. In one clinical series, bladder irrigation successfully cleared clots in most patients, though a small number needed surgical intervention because the retained clots caused urinary retention they could not tolerate.1PubMed Central. A simple and effective method for bladder blood clot evacuation using hydrogen peroxide
The shape and color of clots sometimes hint at where the bleeding originates. Worm-like, elongated clots often form in the ureters (the tubes connecting the kidneys to the bladder), suggesting a kidney or upper-tract source. Rounder, amorphous clots tend to form in the bladder itself. These are rough guides, not diagnoses, but they can help a urologist decide which tests to prioritize.
An Enlarged Prostate
Benign prostatic hyperplasia, the gradual enlargement of the prostate that affects most men as they age, is one of the most frequently identified causes of blood in the urine in older males. The prostate sits at the base of the bladder and wraps around the urethra. As it grows, its blood supply increases, and those extra vessels can rupture and bleed. Men who have had a prior prostate procedure can also experience bleeding from the vascular regrowth that occurs during healing.2PubMed Central. Hematuria Secondary to Benign Prostatic Hyperplasia: Retrospective Analysis of 166 Men Identified in a Single One Stop Hematuria Clinic The bleeding is often intermittent and painless, which can lull you into thinking it resolved on its own, but recurrence is common.
When the bleeding from an enlarged prostate does not respond to conservative measures like medications or catheter irrigation, a procedure called prostatic artery embolization can be effective. One study found that the procedure resolved hematuria in every treated patient at three months, with no recurrence over six months of follow-up.3African Journal of Urology. Safety and efficacy of prostatic artery embolization in patients with hematuria due to benign prostate hyperplasia It works by cutting off blood flow to the overactive prostatic vessels. Larger studies have confirmed that prostatic artery embolization is a reasonable option for men with bleeding caused by an enlarged prostate who are not good candidates for surgery.4PubMed. Prostatic Artery Embolization for Control of Gross Hematuria in Patients with Benign Prostatic Hyperplasia: A Single-Center Retrospective Study in 20 Patients
Bladder and Kidney Cancers
This is the diagnosis most people fear when they see blood in the toilet, and it is the reason doctors take hematuria seriously. Bladder cancer is one of the more common cancers in men, and painless visible blood in the urine is frequently its first and sometimes its only symptom. A case report illustrates the pattern well: a 67-year-old man presented with painless blood in his urine lasting three weeks, with no other complaints. Workup revealed a urothelial carcinoma of the renal pelvis.5International Journal of Pharmaceutical and Bio-Medical Science. Urothelial Cancer: A Case Report of Macroscopic Hematuria The “painless” part is the red flag: infections and stones usually hurt, so blood without pain is treated with higher suspicion for malignancy.
Kidney cancer, specifically renal cell carcinoma, is another possibility. Hematuria is a common finding in kidney tumors, though many kidney cancers are now caught incidentally on imaging done for other reasons. One important lesson from the clinical literature is that persistent blood in the urine deserves thorough imaging even when initial scans look normal. In one case, a patient’s kidney tumor was missed on both ultrasound and CT scan and was only found on MRI.6PubMed Central. Persistent hematuria caused by renal cell carcinoma after aortic valve replacement and warfarin therapy If the blood keeps appearing and earlier tests were unrevealing, pushing for additional imaging is reasonable.
Risk factors for urinary tract cancers in men include smoking (the single biggest modifiable risk), age over 50, and occupational exposure to certain industrial chemicals. A large screening study used those criteria, defining high-risk subjects as people over 50 with a smoking history of ten or more years or significant environmental exposure.7PubMed Central. High Risk Patients with Hematuria Are Not Evaluated According to Guideline Recommendations If you fit that profile and notice blood in your urine, the urgency of a full workup goes up considerably.
Infections, Stones, and Inflammatory Conditions
Urinary tract infections are a straightforward and usually treatable cause of bloody urine. While UTIs are less common in men than in women, they do occur, particularly in older men with enlarged prostates or those who use catheters. Prostatitis, an infection or inflammation of the prostate itself, can also produce blood in the urine or semen. These infections typically come with other symptoms: burning during urination, frequency, urgency, or pelvic pain.
Kidney stones and bladder stones can scrape the lining of the urinary tract as they move, producing blood that ranges from microscopic to dramatic clots. Stone-related bleeding is usually accompanied by sharp flank or lower abdominal pain, so the cause tends to be more obvious.
A less common but serious inflammatory condition is hemorrhagic cystitis, where the bladder lining becomes severely inflamed and bleeds heavily. This occurs most often after pelvic radiation therapy or certain chemotherapy drugs.8PubMed Central. Challenges and Opportunities in Radiation-induced Hemorrhagic Cystitis Cyclophosphamide, a chemotherapy agent, is particularly notorious for this side effect.9PubMed Central. Case Report: Ataxia telangiectasia with severe hemorrhagic cystitis If you have a history of cancer treatment and are now passing blood clots, radiation-induced or chemotherapy-induced bladder damage should be on the radar. Treatments for radiation cystitis are evolving; one recent study found that bladder instillations with a combination of adelmidrol and sodium hyaluronate resolved visible blood in the urine in over 90% of radiation cystitis patients.10PubMed Central. Efficacy of bladder instillations with adelmidrol and sodium hyaluronate for the treatment of symptomatic radiation cystitis
Exercise-Induced Hematuria
If you are a runner or endurance athlete, you may have experienced blood in your urine after a particularly long or intense workout. This is a well-documented phenomenon, and it has a quirk that is specific to men. A study examining runners who developed visible blood in their urine after running found that in three-quarters of cases, cystoscopy revealed bruise-like contusions on the back wall of the bladder. The mechanism: when the bladder is empty, the posterior wall repeatedly slaps against the bladder neck during the vertical jolting of running. All the patients with these contusions were male, because the prostate anchors the male bladder neck more firmly to the pelvic floor, creating a harder surface for the bladder wall to hit.11PubMed Central. Macroscopic hematuria caused by running-induced traumatic bladder mucosal contusions The good news is that the bleeding resolved in every case once running stopped, without any treatment needed.
There is a catch, though. Exercise-induced hematuria is supposed to be a self-limiting condition, but occasionally the damaged blood vessels do not heal cleanly. One case report documented a patient whose exercise-triggered bleeding eventually became recurrent even without exercise, due to abnormal blood vessels that formed at the injury site.12PubMed Central. Recurrent macroscopic haematuria due to bladder blood vessels after exercise induced haematuria So while post-run blood in the urine is common and usually harmless, persistent or recurrent episodes still deserve evaluation. The practical tip for runners: keeping some fluid in your bladder during long runs provides a cushion that reduces the mechanical trauma.
Blood Thinners and Clotting Disorders
Anticoagulant medications like warfarin, heparin, and the newer direct oral anticoagulants do not cause blood in the urine by themselves, but they amplify bleeding from a source that might otherwise have been too minor to notice. If you are on a blood thinner and develop hematuria, the temptation is to blame the medication. Doctors have learned not to stop there. The case of persistent hematuria in a patient on warfarin after heart valve replacement is instructive: the bleeding turned out to be from a kidney tumor, not the anticoagulant.6PubMed Central. Persistent hematuria caused by renal cell carcinoma after aortic valve replacement and warfarin therapy The lesson is clear: blood thinners may unmask an underlying problem rather than being the problem themselves.
On the rarer end, actual clotting disorders can present with hematuria. Acquired hemophilia A, a condition where the body suddenly produces antibodies against one of its own clotting factors, can cause spontaneous bleeding into the skin, muscles, and urinary tract.13PubMed Central. Acquired Hemophilia A Diagnosed Based on Gross Hematuria: A Case Report and Literature Review This is uncommon, but it tends to strike older adults, often without warning. If blood in the urine is accompanied by unusual bruising or bleeding from multiple sites, a clotting disorder moves higher on the list of possibilities.
When It Is Not Actually Blood
Before spiraling into worst-case scenarios, it is worth confirming that what you see is actually blood. Several foods and medications can turn urine red or dark enough to mimic hematuria convincingly. Beets and rhubarb are classic offenders. Among medications, rifampin (used for tuberculosis), phenazopyridine (a bladder pain reliever that is specifically known for turning urine orange-red), and hydroxocobalamin (a form of vitamin B12 used in cyanide poisoning treatment) all cause reddish discoloration that can be mistaken for blood.14PubMed Central. Not all that is red is blood: a curious case of chromaturia A simple urinalysis can distinguish true hematuria from this kind of false alarm. If the dipstick is negative for blood, the red color has a different explanation.
Dehydration can also make normal urine look darker and more alarming than it actually is. Very concentrated urine can appear amber to brownish, which some people interpret as bloody. Again, urinalysis settles the question quickly.
How Doctors Figure Out the Cause
When you show up with blood clots in your urine, the evaluation typically follows a predictable path. A urinalysis and urine culture come first to check for infection and confirm that the blood is real. Blood tests assess kidney function and look for anemia or clotting abnormalities. From there, imaging is the next step. CT urography has become the go-to imaging study for hematuria because it has high accuracy for detecting bladder cancer, upper urinary tract tumors, kidney cancer, and stones in a single scan.15PubMed. CT urography for hematuria It effectively replaces the older approach of doing an ultrasound and a separate dye study.
Cystoscopy, where a thin camera is passed through the urethra into the bladder, is typically performed alongside imaging, especially in men over 40 with visible hematuria. It gives a direct view of the bladder lining and can identify tumors, inflammation, enlarged prostatic vessels, or the mechanical contusions seen in runners. The combination of CT urography and cystoscopy catches the vast majority of significant causes.
In older adults who arrive at the emergency department with blood in their urine, doctors also look at overall clinical indicators. Higher illness-severity scores, fever, confusion, and a greater burden of other medical conditions are red flags for serious complications in this group.16PubMed Central. Predictive Factors for Major Complications and Urological Cancer Diagnosis in Older Adults (≥80 Years) Admitted to the Emergency Department for Hematuria
When to Treat It as an Emergency
Not every episode of bloody urine requires a trip to the emergency room, but some situations do. You should seek immediate care if:
- You cannot urinate: Large clots can block the urethra or bladder outlet entirely, causing painful urinary retention. This needs catheter placement and clot evacuation.
- You feel lightheaded or weak: This suggests significant blood loss. In severe cases of hematuria, patients can become anemic enough to need blood transfusions.
- You have a fever with bloody urine: This combination raises concern for a kidney infection or sepsis, both of which need prompt treatment.
- The bleeding is heavy and continuous: Passing large clots repeatedly, or urine that looks like pure blood, means the bleeding source is active and may need procedural intervention.
For a single episode of mildly pink urine that clears on its own, you still need a medical evaluation, but it can be scheduled with a urologist rather than handled in the ER. The key distinction is severity and associated symptoms. Painless, isolated blood in the urine that you noticed once is still potentially significant, but it is not a middle-of-the-night emergency the way obstructed urine flow or hemodynamic instability would be.
Rare Vascular and Structural Causes
When the standard workup turns up nothing, rarer conditions enter the picture. Nutcracker syndrome, where the left renal vein gets compressed between two major blood vessels in the abdomen, can cause recurrent hematuria that is frustratingly difficult to diagnose. In one reported case, a patient with repeated episodes of gross hematuria and large bladder clots was initially misdiagnosed multiple times before a CT angiogram revealed the compressed vein.17PubMed Central. Beyond bladder clots: Unmasking nutcracker syndrome in refractory hematuria: A case report Nutcracker syndrome tends to affect younger, thinner individuals and is more commonly reported in women, but it can occur in men as well.
Arteriovenous malformations in the kidney, IgA nephropathy (a kidney disease where immune deposits cause episodic bleeding), and even vigorous sexual activity can occasionally produce blood in the urine. These are uncommon enough that they are usually diagnosed only after more common causes have been excluded. If your workup has been thorough and unrevealing, asking your urologist or nephrologist about these possibilities is reasonable.
The Psychological Weight of Unexplained Hematuria
Something that rarely gets discussed is how stressful it is to see blood where it should not be. The anxiety does not go away just because a doctor says “we need to run some tests.” For men who are ultimately diagnosed with bladder cancer, the emotional toll can be substantial. Research into mental health outcomes among bladder cancer patients has found that depression rates after treatment can reach as high as 78%, and male patients in particular showed worsening depression scores during chemotherapy.18UroToday. Mental Health Considerations and Suicide in Bladder Cancer Patients Even when the cause turns out to be benign, the waiting period between noticing blood and getting a definitive answer can be genuinely distressing. If you find yourself in that gap, it is worth knowing that the most common causes of blood in the urine in men are non-cancerous, and that getting the evaluation done promptly is both the best medical move and the fastest way to reduce the uncertainty.
When conservative treatment for prostate-related bleeding is not enough and surgical options carry too much risk, particularly in men with advanced cancer or radiation damage, interventional procedures like artery embolization offer a middle ground.19PubMed Central. The application of prostate artery embolization in the management of intractable prostate bleeding These less invasive options have expanded meaningfully in the last decade, giving men more choices when the bleeding proves stubborn and the standard approaches are not viable.