Blood in urine, known medically as hematuria, has a wide range of causes in men, from urinary tract infections and kidney stones to an enlarged prostate. Most cases turn out to be benign, but visible blood in urine always warrants a medical evaluation because the cause matters, especially for men over 40, where the risk of an underlying urinary tract cancer rises significantly.
Enlarged Prostate
The most common male-specific cause of blood in urine is an enlarged prostate, a condition called benign prostatic hyperplasia (BPH). The prostate gland sits just below the bladder and wraps around the upper part of the urethra. Starting around middle age, it gradually grows larger in most men. As it expands, it compresses the urethra and can obstruct urine flow, leading to symptoms like difficulty starting urination, a weak stream, or feeling like you can’t fully empty your bladder.
The bleeding itself happens because the growing prostate tissue develops congested blood vessels around the prostate and bladder neck. These vessels can rupture and release small amounts of blood into the urine. While BPH is not cancerous, blood in urine from an enlarged prostate still needs to be evaluated, because the same symptom can signal a malignancy or kidney stones that require a completely different response.
Urinary Tract and Kidney Infections
Infections anywhere along the urinary tract can cause blood in urine. Bacteria enter through the urethra and multiply in the bladder, creating inflammation that damages the lining and produces bleeding. The urine may appear red, pink, or brownish. You’ll typically also notice burning during urination, a frequent urgent need to go, or cloudy, strong-smelling urine.
Kidney infections are a more serious form of UTI. Bacteria can travel up from the bladder through the ureters to reach the kidneys, or less commonly, enter the kidneys through the bloodstream. These infections usually come with fever, flank pain, and nausea on top of the urinary symptoms. Prostatitis, an infection or inflammation of the prostate gland itself, produces similar symptoms and is another infection-related cause that’s unique to men.
Kidney and Bladder Stones
Mineral deposits that form in the kidneys or bladder are a frequent cause of hematuria in men. These stones can cause both visible bleeding (urine that looks obviously discolored) and microscopic bleeding that only shows up on a lab test. Small stones may pass without much trouble, but larger ones can scrape the lining of the urinary tract as they move, producing sharp, intense pain in the back or side that radiates toward the groin. Some stones sit in the bladder for a long time and cause intermittent blood in the urine without dramatic pain.
Kidney Disease
The kidneys filter blood through millions of tiny structures called glomeruli, each containing a network of microscopic blood vessels. Normally, these filters let water, minerals, and waste pass through while keeping red blood cells and proteins in the bloodstream. When the glomeruli become inflamed, a condition called glomerulonephritis, the filters break down and allow red blood cells to leak into the urine.
This type of bleeding tends to produce cola-colored or dark brown urine rather than bright red blood. It often comes with foamy urine (a sign that protein is also leaking through), swelling in the legs or face, and high blood pressure. Glomerulonephritis can develop on its own or as a complication of diabetes, infections, or autoimmune conditions. Because it reflects damage to the kidney’s filtering system rather than a problem in the bladder or urethra, it requires a different diagnostic approach and is typically managed by a nephrologist rather than a urologist.
Exercise-Related Bleeding
Strenuous physical activity can cause temporary blood in the urine, a phenomenon first documented in soldiers after long marches in 1881. It is almost always microscopic and resolves on its own. The degree of bleeding correlates with exercise intensity. Two mechanisms are thought to be responsible: direct trauma to the bladder (the bladder wall bouncing against the pelvic bone during running or other high-impact movement) and increased permeability of the kidney’s filters during intense exertion. Contact sports carry a higher risk of producing visible blood in the urine due to direct impact to the kidneys or bladder.
If you notice blood in your urine after a hard workout, it should clear within 24 to 72 hours. Blood that persists beyond that window, or that appears without a clear exercise trigger, points to a different cause.
Bladder and Kidney Cancer
Blood in urine is the most common early sign of bladder cancer. Among men who undergo a full workup for microscopic hematuria, about 2.3% are found to have bladder cancer and 0.3% have kidney cancer. Those numbers may sound small, but the risk is not evenly distributed. Age and the amount of blood detected are the two biggest factors.
For men under 40, the risk of urinary tract cancer with any degree of hematuria stays below 0.5%. For men over 40, even a small amount of blood on a urine test (3 to 10 red blood cells per high-power field) carries a 1.2% cancer risk. At higher levels of bleeding, 26 or more red blood cells per field, the risk jumps to over 4%. Men over 40 with heavy microscopic hematuria face a cancer risk above 6%. Male sex itself is an independent risk factor: men are roughly five times more likely than women to have a urinary tract cancer behind their hematuria.
Painless, visible blood in the urine is the classic red flag for bladder cancer. Unlike infections or stones, cancer-related bleeding often comes and goes without any other symptoms, which can lead people to dismiss it after the first episode resolves.
How Doctors Evaluate Blood in Urine
A positive dipstick test alone is not enough to confirm hematuria. The standard definition requires more than 3 red blood cells per high-power field on microscopic examination of a properly collected urine sample. If that threshold is met, your doctor will take a detailed history, check your blood pressure, and run a blood test to assess kidney function. Smoking history matters here because it substantially increases the risk that hematuria is cancer-related.
From there, doctors categorize you into low, intermediate, or high risk for an underlying malignancy. Low-risk patients typically just need a repeat urinalysis within six months. Intermediate-risk patients are recommended for a cystoscopy (a thin camera inserted into the bladder) along with an ultrasound of the kidneys. High-risk patients get cystoscopy plus a CT scan that images the entire urinary tract.
For visible blood in the urine, CT imaging is highly accurate, with 100% sensitivity and 95% specificity for detecting bladder tumors. Cystoscopy on its own catches about 81% of tumors, which is why the two tests are often used together for high-risk patients.
When Blood in Urine Needs Urgent Attention
Any visible blood in the urine, even a single episode, warrants contacting a doctor. Certain accompanying symptoms raise the urgency: fever and flank pain suggest an active kidney infection, severe abdominal or lower back pain may indicate a stone or other obstruction, and difficulty urinating or passing clots could signal significant bleeding that needs immediate attention. If symptoms are severe, an urgent care or emergency visit is appropriate rather than waiting for a scheduled appointment.