Blood in urine is usually not a sign of cancer, but it always warrants medical attention. In a large study of over 3,500 people referred for evaluation, about 10% turned out to have a urinary tract cancer. The other 90% had a benign explanation: an infection, a kidney stone, an enlarged prostate, or even just a hard workout. The cause matters enormously, and many of the common ones are straightforward to treat.
Visible Blood vs. Blood Only Found on a Test
There are two types of blood in urine, and the distinction shapes how urgently your doctor will investigate. Visible blood, where your urine looks pink, red, or cola-colored, carries a higher concern for cancer. In one prospective study, 13.2% of people with visible blood had a urinary tract cancer, compared to 3.1% of those whose blood was only detected under a microscope during a routine urinalysis.
Microscopic blood is defined as three or more red blood cells per high-power field on a urine sample. You won’t see any color change. It often shows up incidentally during a checkup, and while it still needs follow-up, the odds of a serious cause are lower.
Enlarged Prostate
Benign prostatic hyperplasia, or an enlarged prostate, is one of the most common reasons men over 50 notice blood in their urine. As the prostate grows, it creates irregular tissue with fragile blood vessels near the surface. Urine flowing through the narrowed urethra hits these irregular surfaces with turbulent force, raising pressure in the surrounding tissue and rupturing small vessels. The result can range from a faint pink tinge to more dramatic bleeding episodes.
An enlarged prostate also causes difficulty starting urination, a weak stream, frequent nighttime bathroom trips, and a feeling that your bladder isn’t fully empty. If these symptoms sound familiar alongside the blood, the prostate is a likely culprit. Prostatitis, an infection or inflammation of the prostate, produces similar symptoms and can also cause bloody urine.
Infections
Urinary tract infections are less common in men than in women, but they do happen, particularly in older men or those with an enlarged prostate that prevents complete bladder emptying. Bacteria irritate the lining of the bladder or urethra, causing inflammation that leads to bleeding. Along with blood, you’ll typically notice burning during urination, a strong urge to urinate frequently, and cloudy or foul-smelling urine. Kidney infections add flank pain and fever to the picture.
Kidney and Bladder Stones
Stones form when minerals in your urine crystallize and clump together. As a stone moves through the urinary tract, its rough edges scrape the delicate lining, causing bleeding. Kidney stones are notorious for severe, wave-like pain in the back or side that radiates toward the groin. Bladder stones can cause pain in the lower abdomen and interruption of urine flow. Small stones sometimes pass without much pain but still leave enough blood to change the color of your urine.
Bladder and Kidney Cancer
Cancer is the diagnosis men worry about most, and visible blood in the urine is the most common early symptom of bladder cancer. The numbers provide useful context: among high-risk patients (age 60 or older, history of smoking, or visible blood), about 11% with visible blood were found to have bladder cancer. Among high-risk patients with only microscopic blood, that rate dropped to 2.6%. Kidney cancer and prostate cancer can also cause bleeding into the urinary tract, though prostate cancer more often presents with other symptoms first.
Smoking is the single biggest modifiable risk factor for bladder cancer. The risk calculation your doctor uses explicitly accounts for your smoking history, measured in pack-years. A man over 60 with a 30-plus pack-year history and visible blood in his urine falls into the highest risk category and will get the most thorough workup.
Exercise-Induced Bleeding
Intense physical activity, especially long-distance running, can cause blood to appear in urine without any underlying disease. Two mechanisms are at play. First, during hard exercise, blood flow to the kidneys drops sharply as the body redirects circulation to working muscles. This temporary reduction in kidney blood supply can damage small vessels enough to leak red blood cells. Second, in runners specifically, the empty bladder wall slaps against its own base with each stride, creating bruise-like injuries on the bladder lining.
Exercise-induced blood in the urine typically clears within 24 to 48 hours of rest. If it doesn’t, something else is going on.
Medications and Foods That Mimic Blood
Before assuming the worst, consider whether something you swallowed could be coloring your urine. Beets, blackberries, and rhubarb can turn urine pink or red. Several medications do the same: the tuberculosis drug rifampin turns urine reddish-orange, phenazopyridine (a common bladder pain reliever) turns it bright orange-red, and laxatives containing senna can cause a similar color shift. None of these represent actual bleeding.
On the other hand, blood thinners and aspirin don’t change your urine color on their own, but they can make you more prone to actual bleeding from the urinary tract. If you take these medications and notice blood in your urine, the blood is real and still needs evaluation.
How Doctors Evaluate Blood in Urine
Your evaluation depends on your age, how much blood is present, and your risk factors. Doctors use a three-tier system to decide how aggressively to investigate.
- Lower risk (men under 40, small amounts of microscopic blood, nonsmoker): a repeat urinalysis in six months may be sufficient, though imaging and a closer look at the bladder are also reasonable.
- Intermediate risk (men 40 to 59, moderate microscopic blood, or some smoking history): an ultrasound of the kidneys and a cystoscopy, where a thin camera is passed through the urethra to inspect the bladder lining, are recommended.
- Higher risk (men 60 or older, heavy microscopic blood, significant smoking history, or any episode of visible blood): a cystoscopy plus CT urography, which is a specialized CT scan of the entire urinary tract, is the standard approach.
The goal of this tiered approach is to catch cancers early while sparing younger, lower-risk men from unnecessary procedures. Regardless of your age, any episode of visible blood in the urine puts you in the higher-risk evaluation category automatically.
Other Less Common Causes
A few other conditions round out the list. Glomerulonephritis is a type of kidney disease where the tiny filters inside the kidneys become inflamed, often as part of a systemic condition like diabetes or sometimes after a bacterial infection like strep throat. It typically causes microscopic blood along with protein in the urine. Blood-clotting disorders like hemophilia and sickle cell disease can also lead to urinary bleeding. Trauma to the kidneys or bladder from a fall, car accident, or contact sport is another possibility, and recent urinary tract procedures like catheter placement or a prostate biopsy can cause temporary bleeding that resolves on its own.