Blood in urine, called hematuria, has a wide range of causes in men, from benign prostate enlargement and kidney stones to urinary tract infections and, less commonly, bladder or kidney cancer. Sometimes it’s visible, turning urine pink, red, or cola-colored. Other times it’s microscopic, only detected when a urine sample is examined under a microscope. Either way, it warrants investigation because the cause matters.
Enlarged Prostate
Benign prostatic hyperplasia (BPH), the gradual enlargement of the prostate that affects most men as they age, is one of the most common reasons for blood in urine. As the prostate grows, blood vessels in the prostate and at the bladder neck become congested. These swollen vessels can leak small amounts of blood into the urine, sometimes without any pain at all.
BPH usually comes with other urinary symptoms that fall into two categories. Storage symptoms include needing to urinate frequently, feeling sudden urgency, and waking up multiple times at night to pee. Emptying symptoms include a weak stream, difficulty starting urination, stopping and starting mid-stream, and dribbling afterward. If you’re experiencing blood in your urine alongside these kinds of changes, an enlarged prostate is a likely contributor, especially if you’re over 50.
Urinary Tract Infections and Prostatitis
UTIs are less common in men than in women, but they do happen, and they can cause blood in the urine along with burning during urination, frequent urges to go, and cloudy or foul-smelling urine. Bacteria irritate the lining of the bladder or urethra, which can cause small amounts of bleeding.
Prostatitis, an infection or inflammation of the prostate itself, is another possibility. It can produce similar urinary symptoms plus pelvic pain, pain during ejaculation, or flu-like symptoms if the infection is bacterial. Both conditions are typically treatable with antibiotics when bacteria are the cause.
Kidney Stones
Kidney stones are a frequent cause of blood in the urine in men of all ages. As a stone moves through the urinary tract, its rough edges scrape against the delicate lining of the ureter or bladder, causing bleeding. The blood may be visible or only detectable on a lab test.
The hallmark of a kidney stone is sudden, severe pain that often starts in your back or side and radiates toward your groin. The pain typically comes in waves. You might also notice nausea, vomiting, or an urgent need to urinate. Small stones often pass on their own within days to weeks, though larger ones may need medical intervention to break up or remove.
Bladder and Kidney Cancer
Blood in the urine is the most common early sign of bladder cancer, and men are significantly more likely to develop it than women. The urine may appear bright red or cola-colored, or the blood may only show up on a lab test. Notably, bladder cancer bleeding is often painless, which can cause people to dismiss it.
Smoking is the single biggest modifiable risk factor. Smokers are three times more likely to develop bladder cancer because the body filters harmful chemicals from tobacco smoke and excretes them through urine. Over time, these chemicals damage the bladder lining. Kidney cancer can also cause blood in the urine, though it tends to produce symptoms later in the disease. Age, chemical exposure at work, and a history of chronic bladder irritation also raise risk.
Not every case of hematuria points to cancer. But painless blood in the urine, particularly in men over 40 who smoke or have smoked, is something that needs prompt evaluation.
IgA Nephropathy
In younger men, particularly those in their late teens through late 30s, a kidney condition called IgA nephropathy is a notable cause of recurrent blood in the urine. It occurs when an antibody called IgA builds up in the kidneys and causes inflammation in the tiny filters that clean your blood. Men are more likely to develop it than women, and there appears to be a genetic component.
A hallmark pattern is episodes of visible blood in the urine that coincide with upper respiratory infections or other illnesses. Between episodes, urine may look normal, but microscopic blood often persists. Over years, the ongoing inflammation can gradually damage the kidneys, so diagnosis and monitoring matter even when symptoms seem mild. Diagnosis typically involves blood and urine tests to check kidney function, blood pressure monitoring, and sometimes a kidney biopsy to confirm the condition.
Exercise-Induced Hematuria
Strenuous physical activity, particularly long-distance running, cycling, or intense contact sports, can temporarily cause blood in the urine. This happens in people with no underlying kidney or urinary tract disease and resolves with rest. The exact mechanism isn’t fully understood, but it likely involves a combination of minor bladder trauma from repeated impact, reduced blood flow to the kidneys during exertion, and the breakdown of red blood cells.
If you notice blood in your urine after a hard workout, the key distinction is that it clears up within 24 to 72 hours of rest. Blood that persists beyond that, or that appears without a clear exercise trigger, needs further evaluation.
Blood Thinners and Other Medications
If you take blood thinners, they can either cause hematuria directly or unmask bleeding from a previously silent problem. In one study of patients with visible blood in the urine, over 76% were taking anticoagulants or antiplatelet medications. This includes common drugs like warfarin, rivaroxaban, apixaban, aspirin, and clopidogrel.
These medications work by interfering with your body’s clotting process in different ways, but the practical result is the same: minor bleeding that your body would normally stop on its own becomes more noticeable. That said, blood thinners should not be assumed to be the sole explanation. People on these medications who develop hematuria still need to be evaluated for underlying causes, because the bleeding may be revealing a problem like a tumor or stone that would otherwise have gone unnoticed.
How Hematuria Is Evaluated
The diagnostic starting point is a urinalysis. Microscopic hematuria is formally defined as more than 3 red blood cells per high-power field on a properly collected urine sample. From there, the American Urological Association recommends a risk-based approach that considers your age, smoking history, the amount of blood, and other factors.
For lower-risk patients, the first step is often a repeat urinalysis within six months to see if the blood persists. Intermediate-risk patients typically undergo a cystoscopy (a thin camera inserted through the urethra to visually inspect the bladder) along with a kidney ultrasound. For higher-risk patients, particularly older men, smokers, or those with large amounts of blood, the workup is more thorough: cystoscopy plus a CT scan that images the entire urinary tract from kidneys to bladder.
The evaluation is designed to be proportional to your risk. Not everyone with a trace of blood in their urine needs a CT scan, but persistent or visible hematuria, especially with risk factors, calls for a complete workup. The goal is straightforward: identify or rule out a serious cause so that the right treatment can start early.