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

Seeing blood in your urine—medically termed hematuria—can be alarming, but it's more common than many people realize. While occasional, mild hematuria may not always signal a serious condition, it should never be ignored. This symptom can range from microscopic (detectable only under a microscope) to gross (visible to the naked eye), and its underlying causes vary widely—from benign and easily treatable issues to conditions requiring prompt evaluation and intervention.

Common Causes of Hematuria

1. Urinary Tract Infections (UTIs)

One of the most frequent culprits behind blood in urine is a urinary tract infection. UTIs trigger inflammation in the bladder, urethra, or kidneys, leading to red blood cells leaking into the urine. Alongside hematuria, patients often experience classic symptoms such as urinary frequency, urgency, burning during urination (dysuria), and lower abdominal discomfort. A standard urinalysis typically reveals not only red blood cells but also elevated white blood cells and nitrites—clear indicators of infection. Antibiotics usually resolve the issue quickly, but recurrent UTIs warrant further investigation to rule out anatomical abnormalities or chronic conditions.

2. Kidney or Bladder Stones

Urolithiasis—the formation of stones in the kidneys, ureters, or bladder—is another leading cause of visible hematuria. As stones move through the urinary tract, they can scratch or irritate delicate mucosal linings, resulting in bleeding. This type of hematuria is often accompanied by severe, colicky flank or abdominal pain (renal colic), nausea, and sometimes vomiting. Imaging—such as non-contrast CT scans or renal/bladder ultrasound—is highly effective for detecting stones and assessing their size and location. Smaller stones may pass spontaneously with hydration and pain management, while larger ones may require lithotripsy or surgical removal.

3. Asymptomatic Microscopic Hematuria

In some cases, blood appears in urine without any other noticeable symptoms—a scenario known as asymptomatic microscopic hematuria. Here, urinalysis shows red blood cells, but all other parameters (like white blood cells, protein, nitrites, and pH) remain within normal limits. While this can occasionally stem from vigorous exercise, menstruation, or certain medications (e.g., anticoagulants), it should always prompt a thorough urologic workup—especially in adults over 40—to exclude early-stage malignancies or glomerular disease.

Red Flags: When Hematuria May Signal Something Serious

Painless Gross Hematuria in Older Adults

For individuals aged 50 and above, painless visible blood in the urine is considered a potential warning sign of urothelial cancer—including tumors of the bladder, ureter, or renal pelvis. Unlike infection- or stone-related hematuria, this form rarely presents with pain, urgency, or fever. It may appear intermittently and even resolve temporarily, making it easy to dismiss. Yet, early detection dramatically improves outcomes. Diagnostic steps typically include urine cytology, cystoscopy (a minimally invasive camera exam of the bladder), and cross-sectional imaging like CT urography.

Hematuria Following Trauma

Any recent injury to the lower back, abdomen, or pelvis—including falls, car accidents, or sports collisions—can damage the kidneys, bladder, or urethra and lead to hematuria. Even seemingly minor trauma warrants medical assessment. A detailed history, physical exam, and imaging studies—such as CT scan with contrast or focused renal ultrasound—help determine the extent of injury and guide treatment, which may range from observation to emergency surgery.

When to See a Doctor—and What to Expect

If you notice blood in your urine—even once—schedule an appointment with your primary care provider or a urologist. Be prepared to discuss timing, frequency, associated symptoms (pain, fever, fatigue), medication use, and family history. Initial testing almost always includes a comprehensive urinalysis, urine culture, and blood tests (e.g., creatinine, CBC). Depending on findings, your doctor may recommend advanced diagnostics like ultrasound, CT urography, MRI, or cystoscopy.

Remember: Hematuria is a symptom—not a diagnosis. Its significance lies in what it reveals about your urinary health. With timely evaluation and evidence-based care, most causes are manageable, treatable, and sometimes entirely preventable. Don't delay—your peace of mind and long-term wellness depend on taking this sign seriously.