What Causes Blood in Urine (Hematuria)? Understanding Common Causes and When to Seek Medical Attention

Hematuria—the medical term for blood in the urine—can be alarming, whether it's visible to the naked eye (gross hematuria) or detectable only under a microscope (microscopic hematuria). While occasional, asymptomatic microscopic hematuria may occur without serious underlying issues, persistent or symptomatic blood in urine always warrants professional evaluation. It's not a diagnosis itself, but rather an important clinical sign pointing to potential conditions affecting the urinary tract or systemic health.

Most Common Causes of Hematuria

Kidney stones are among the leading causes of visible hematuria—especially when accompanied by severe, colicky flank or abdominal pain (often called renal colic). As stones move through the ureter, they irritate and abrade the delicate lining of the urinary tract, resulting in bleeding. You may also notice intermittent urine flow, a telltale sign that a stone is temporarily obstructing the ureter or bladder outlet.

Urinary tract infections (UTIs), particularly when severe or recurrent, frequently cause hematuria alongside classic symptoms like urgency, frequency, burning during urination, and sometimes pelvic discomfort or low-grade fever. In older adults or immunocompromised individuals, UTIs can progress silently—making routine urinalysis especially valuable for early detection.

Other Important Considerations

Glomerulonephritis—inflammation of the kidney's filtering units—often presents with microscopic hematuria, sometimes combined with proteinuria, elevated blood pressure, or swelling (edema). Unlike stone-related bleeding, this type rarely causes pain but may indicate an autoimmune condition, infection-triggered response, or chronic kidney disease.

Beyond the kidneys and bladder, hematuria can also signal systemic disorders, including blood clotting abnormalities (e.g., hemophilia or anticoagulant use), vasculitis, sickle cell disease, or even certain cancers—such as bladder, kidney, or prostate cancer. While less common in younger, otherwise healthy individuals, age, smoking history, occupational exposures (e.g., aromatic amines), and persistent painless hematuria significantly increase cancer risk and require thorough urologic workup.

Why Timely Evaluation Matters

Don't assume blood in your urine will "go away on its own." Even one episode of gross hematuria in adults over 35 should prompt a comprehensive assessment—including urinalysis, urine culture, renal function tests, imaging (like ultrasound or CT urogram), and possibly cystoscopy. Early identification leads to faster treatment, better outcomes, and peace of mind. Remember: Hematuria is your body's red flag—not something to ignore or self-diagnose.