Hematuria — the medical term for blood in the urine — affects millions of people each year and can range from invisible traces detected on a lab test to visibly red or brown urine. Whether it turns out to be something minor or a sign of a more serious condition, understanding potential causes helps you have a more informed conversation with your doctor. Here are 10 common reasons hematuria occurs and what each one means for your health.
1. Urinary Tract Infections
Urinary tract infections, or UTIs, are among the most frequent causes of hematuria, especially in women. Bacteria enter the urethra and irritate the lining of the bladder, which can cause bleeding along with burning during urination and a frequent urge to go. Research suggests that UTIs account for a significant proportion of hematuria cases seen in primary care settings. According to NIH, evidence-based protocols help clinicians distinguish infection-related hematuria from more serious underlying causes. If you suspect a UTI, prompt medical evaluation and a course of antibiotics can typically resolve both the infection and the bleeding.
2. Kidney Stones
Kidney stones form when minerals crystallize inside the kidneys, and they can scratch the urinary tract lining as they move. This often produces visible blood in the urine alongside severe flank or lower abdominal pain. Stones as small as a grain of sand can cause significant irritation to delicate tissue. Staying well-hydrated is one of the simplest strategies to help reduce your risk of developing stones. If you notice blood in your urine paired with sharp pain, seek medical attention promptly to determine stone size and the best treatment approach.
3. Bladder Infections and Inflammation
Beyond typical UTIs, conditions like interstitial cystitis can cause chronic bladder inflammation and lead to microscopic or gross hematuria. The bladder wall becomes irritated and may bleed even without a bacterial infection present. Symptoms often include pelvic pressure, painful urination, and an urgent need to urinate frequently. Doctors typically use urine cultures and cystoscopy to differentiate inflammatory conditions from infections. Tracking your symptoms in a journal can help your healthcare provider pinpoint the cause and develop a targeted treatment plan.
4. Enlarged Prostate
For men over 50, an enlarged prostate — known as benign prostatic hyperplasia — is a common cause of hematuria. As the prostate grows, it can compress the urethra and create pressure on nearby blood vessels. This pressure sometimes causes small amounts of blood to appear in the urine. Clinical evidence shows that prostate-related hematuria is typically benign but still warrants evaluation. A visit to a urologist can help rule out prostate cancer and determine whether medication or monitoring is the right next step.
5. Kidney Disease and Glomerulonephritis
Glomerulonephritis is an inflammation of the tiny filtering units in the kidneys called glomeruli. When these filters become damaged, red blood cells can leak into the urine. According to PubMed, glomerular indicators like red cell casts and proteinuria typically warrant a nephrology referral for further investigation. This type of hematuria may be linked to autoimmune disorders, infections, or inherited conditions like IgA nephropathy. Early detection through routine urinalysis can make a meaningful difference in preserving long-term kidney function.
6. Vigorous Exercise
Sometimes called “runner’s hematuria” or “march hematuria,” blood in the urine can appear after intense physical activity. Long-distance running, cycling, and contact sports are the most commonly associated activities. The exact mechanism is not fully understood, but repeated impact on the bladder and dehydration-related stress on the kidneys likely play roles. Studies indicate this form of hematuria is usually temporary and resolves within 48 to 72 hours of rest. If blood persists beyond that window, it is wise to check with a doctor to rule out other causes.
7. Medications and Blood Thinners
Certain medications can increase your risk of hematuria. Blood thinners like warfarin and heparin reduce your blood’s ability to clot, which may allow small amounts of blood to enter the urine. Aspirin, some antibiotics like penicillin, and even the cancer drug cyclophosphamide have been linked to urinary bleeding. It is important to note that medication-related hematuria does not mean you should stop taking your prescription. Instead, contact your prescribing doctor so they can evaluate whether a dosage adjustment or additional testing is needed.
8. Bladder or Kidney Cancer
While far less common than infections or stones, hematuria can sometimes signal bladder or kidney cancer, particularly in adults over 40. Painless gross hematuria is considered a red-flag symptom that requires thorough investigation. A PubMed review emphasizes that risk stratification is essential in the initial evaluation of hematuria to identify serious causes like renal malignancy early. Diagnostic tools such as CT urography, cystoscopy, and urine cytology are commonly used for assessment. Never ignore persistent or unexplained blood in your urine, even if it comes and goes without pain.
9. Inherited Disorders
Genetic conditions like sickle cell disease and Alport syndrome can cause chronic or recurrent hematuria starting in childhood. Sickle cell disease damages small blood vessels in the kidneys, leading to microscopic bleeding over time. Alport syndrome involves a defect in the collagen within the kidney’s filtering membranes. These conditions often run in families, so a detailed family medical history can be a valuable diagnostic clue. If inherited kidney disease is suspected, genetic counseling and early nephrology care may help slow disease progression.
10. Diagnostic Imaging Discrepancies
Interestingly, how hematuria is evaluated can vary depending on which clinical guidelines your doctor follows. Research published in PubMed found that North American guidelines from the ACR, AUA, and CUA show notable discrepancies in imaging recommendations, particularly regarding ultrasound versus CT urography for microhematuria. This means your workup experience may differ based on your healthcare setting or risk level. Understanding these differences can empower you to ask informed questions about which imaging approach is right for your situation. Discuss the options with your urologist to ensure your evaluation is both thorough and appropriate for your personal risk profile.
Hematuria has a wide range of causes, from the very common and easily treatable to the rare and more serious. The single most important step you can take is to never ignore blood in your urine — schedule an appointment with your healthcare provider so they can perform the appropriate tests and guide you toward the right diagnosis and treatment plan.
Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making health decisions.
