Blood in your urine means something is causing red blood cells to leak into your urinary tract, anywhere from your kidneys down to your urethra. The cause is often minor, like a urinary tract infection or intense exercise, but it can also signal something more serious like kidney stones or, less commonly, cancer. Even a single episode is worth investigating.
Sometimes you can see the blood yourself, turning urine pink, red, or brownish. Other times it’s invisible to the naked eye and only shows up on a lab test. Both forms matter, and the workup your doctor recommends depends on your age, symptoms, and risk factors.
Visible vs. Invisible Blood
Visible blood in urine (called gross hematuria) is hard to miss. Your urine may look pink, red, cola-colored, or have visible clots. It takes very little blood to change the color, so even a dramatic-looking episode doesn’t necessarily mean heavy bleeding.
Microscopic hematuria, by contrast, is blood you can’t see. It’s defined as more than 3 red blood cells per high-power field under a microscope. This is typically discovered incidentally during a routine urinalysis. Because there are no visible clues, many people don’t know they have it until a doctor mentions it.
Common Causes
Urinary tract infections are one of the most frequent explanations, especially in women. Bacteria enter the urethra and multiply in the bladder, causing inflammation that leads to bleeding. You’ll usually also notice burning with urination, urgency, or cloudy urine.
Kidney stones and bladder stones can scrape or irritate the lining of the urinary tract as they move. The hallmark is intense, crampy pain in the back or side (flank pain) that comes in waves. If you have blood in your urine along with colicky pain, a stone is a likely suspect.
In men over 50, an enlarged prostate is a common culprit. The prostate surrounds the urethra, and as it grows, it can press on surrounding tissue and cause bleeding. Prostate infections (prostatitis) produce similar symptoms: difficulty urinating, a persistent urge to go, and blood-tinged urine.
Other recognized causes include:
- Vigorous exercise. Long-distance running and other intense activity can trigger temporary bleeding that resolves with rest.
- Recent urinary tract procedures. Catheterization, biopsies, or other interventions can irritate tissue.
- Trauma. A blow to the kidneys or lower abdomen.
- Endometriosis. Uterine tissue growing near the bladder or urinary tract.
- Sexual activity. Occasionally causes minor irritation and short-lived bleeding.
More Serious Causes
Bladder, kidney, and prostate cancers can all cause blood in urine. This is the reason doctors take hematuria seriously even when there’s no pain. Painless hematuria, particularly in adults over 40 or people with a smoking history, prompts an investigation for malignancy. Most people with blood in their urine do not have cancer, but ruling it out is a standard part of the evaluation.
Kidney diseases that affect the glomeruli (the tiny filtering units inside your kidneys) can also cause microscopic blood to leak into urine. These conditions sometimes follow a bacterial or viral infection, such as strep throat or hepatitis, and may show up as blood in urine that’s only detectable in the lab.
Blood-clotting disorders like hemophilia and sickle cell disease are less common causes but important to consider, especially if you bruise easily or have a known bleeding condition. Certain medications, including blood thinners and aspirin, can also increase the likelihood of blood appearing in urine, though the medication itself isn’t always the root cause. It may simply unmask an underlying problem.
When It’s Not Actually Blood
Red or pink urine isn’t always hematuria. Beets, blackberries, and rhubarb can all turn urine red or pink and alarm you for no medical reason. Certain medications do the same: the tuberculosis drug rifampin turns urine reddish-orange, as does phenazopyridine (a common over-the-counter urinary pain reliever). Constipation medications containing senna can also cause a color change. If you’ve recently eaten any of these foods or taken these medications, that may explain what you’re seeing. A simple urinalysis will confirm whether actual blood cells are present.
Exercise-Induced Hematuria
Blood in urine after a hard workout, especially long-distance running, is well documented. It occurs in people with no underlying kidney or urinary tract disease and resolves with rest. The exact mechanism isn’t fully understood, but repeated impact on the bladder and increased blood flow to the kidneys during exertion both play a role. If you notice pink or red urine after a strenuous run or workout, it’s worth mentioning to your doctor, but it typically clears within 24 to 72 hours. Persistent bleeding after rest needs further evaluation.
What Pain Tells You
Whether or not you have pain alongside the bleeding is a useful clue. Colicky, wave-like pain in your side or back strongly suggests a kidney stone. Burning or stinging during urination points toward infection. Blood with difficulty urinating or a weak stream, particularly in older men, often implicates the prostate.
Painless blood in urine is actually the pattern that warrants the most careful investigation. Without pain or other obvious symptoms, infection and stones become less likely explanations, and your doctor will want to rule out malignancy and kidney disease. This doesn’t mean painless hematuria is always dangerous, but it does mean it shouldn’t be dismissed.
How Doctors Evaluate It
The evaluation starts with a thorough medical history and a physical exam, including a blood pressure check and a blood test to assess kidney function. Your doctor will ask about smoking history, recent infections, medications, family history of kidney disease, and any urinary symptoms.
What happens next depends on your risk level. The American Urological Association categorizes patients into low, intermediate, and high risk for malignancy based on factors like age, smoking status, the amount of blood found, and whether you’ve had visible blood in your urine.
If you’re considered low risk, your doctor will likely repeat the urinalysis within six months rather than ordering invasive tests right away. For intermediate-risk patients, the standard recommendation is an ultrasound of the kidneys plus a cystoscopy, a procedure where a thin camera is inserted through the urethra to visually inspect the bladder lining. High-risk patients typically get both a cystoscopy and a CT scan of the urinary tract to get detailed images of the kidneys, ureters, and bladder.
If you fall in the intermediate category and want to avoid cystoscopy, some doctors may offer urine-based tests that look for cancer markers, though an ultrasound is still recommended alongside them. These alternatives aren’t a perfect substitute for direct visualization of the bladder, and your doctor should walk you through the trade-offs.
Symptoms That Need Urgent Attention
Most causes of blood in urine aren’t emergencies, but a few situations call for prompt medical care. If you’re passing large clots, can’t urinate despite the urge, or have blood in your urine along with severe flank pain and fever, you should be seen quickly. Fever plus bloody urine can indicate a kidney infection, which can progress rapidly. Similarly, if you’re on blood thinners and notice persistent or heavy bleeding, contact your doctor the same day rather than waiting for a routine appointment.