Causes
Blood can enter the urine anywhere along the urinary tract, from the kidneys to the urethra:- Urinary tract infections: Bladder and kidney infections inflame the urinary lining, often with burning and urgency.
- Kidney stones: Stones scrape the urinary tract as they form or pass, classically with severe, cramping flank pain.
- Enlarged prostate: In older men, benign prostatic hyperplasia is a frequent source of both visible and microscopic blood.
- Kidney disease: Inflammation of the kidney's filtering units (glomerulonephritis) can leak blood and protein into the urine, sometimes after an infection.
- Vigorous exercise: Long-distance running can cause temporary, harmless hematuria that clears within days.
- Recent procedures or injury: A urinary catheter, a recent prostate or bladder procedure, or a direct blow to the flank can all cause short-lived bleeding.
- Cancers: Tumors of the bladder, kidney, or prostate can bleed - painless visible blood in an older adult, especially a current or former smoker, is the classic warning sign.
Symptoms
Hematuria itself may be the only finding, and visible blood is often painless. Accompanying symptoms help point to the cause: burning and frequency suggest infection; severe one-sided flank pain suggests a stone; a weak stream and nighttime urination in a man suggests prostate enlargement; and swelling with foamy urine points toward a kidney (glomerular) cause. It is also worth knowing that beets, blackberries, certain food dyes, and some medications can turn urine red without any blood at all - a urine test settles the question.Diagnosis
Evaluation begins with a urinalysis and microscopic examination to confirm true red blood cells, plus a urine culture to check for infection. Depending on your age, risk factors, and findings, your physician may order blood tests of kidney function, a CT scan of the urinary tract, and referral to a urologist for cystoscopy - a thin, flexible camera examination of the bladder that is the definitive way to inspect its lining. Microscopic hematuria found on a routine test is typically confirmed on a repeat sample before a larger workup begins.Treatment
Treatment targets the cause, not the blood itself: antibiotics for infection, stone management, treatment of prostate enlargement, or specialist care for kidney disease and tumors. When a thorough evaluation finds no cause - a common and reassuring outcome - your physician may simply recheck a urine sample and your blood pressure periodically.When to Seek Immediate Care
Call your physician the same day, or go to an emergency department, if blood in the urine comes with:- Clots or trouble urinating: Clots can block the bladder outlet and cause painful urinary retention.
- Fever, chills, or flank pain with nausea: These point toward a kidney infection needing prompt treatment.
- Lightheadedness or a racing heartbeat: Heavier or ongoing blood loss should be assessed urgently.
- Severe, unrelenting one-sided flank pain: Often an obstructing stone, which may need urgent intervention.
How Blood in the Urine Is Worked Up
Hematuria is a finding rather than a disease, and the point of the workup is to find the few serious causes among the many harmless ones without over-testing everyone. The details below explain how that decision is made, what commonly imitates blood, and what happens when nothing is found.
Confirm it before anything else
A dipstick alone is not enough: it reacts to muscle pigment after hard exercise and to hemoglobin from other causes, so a microscopic count of red cells on a fresh sample is what counts. The sample is repeated a few days after finishing treatment for a urinary tract infection, away from menstruation, and at least two days after running or cycling, since each of those produces temporary blood. Beets, rifampin, phenazopyridine, and some food dyes redden urine without any blood at all.
The workup is matched to risk
Visible blood in an adult gets a full evaluation: a CT urogram to image the kidneys and ureters, and cystoscopy to inspect the bladder lining directly. For microscopic blood, the extent of testing depends on age, smoking history, the amount of blood, and prior episodes. Younger non-smokers with a small amount of blood may need only an ultrasound and a repeat test, while older adults and current or former smokers get the full evaluation, because smoking is the strongest risk factor for bladder cancer. Our microscopic hematuria article walks through what to expect from each step.
Blood thinners do not explain it
A person taking apixaban or warfarin for atrial fibrillation who develops hematuria is evaluated exactly as anyone else would be, because the drug usually unmasks a source that was already there rather than causing bleeding on its own. Stopping the anticoagulant is not part of the workup and carries its own risk.
Kidney or bladder: the pattern points
Blood with protein in the urine, misshapen red cells on microscopy, high blood pressure, or swelling points to the kidney's filters rather than the urinary tract, and that pattern goes to nephrology rather than cystoscopy; the chronic kidney disease page explains what those tests mean. Severe one-sided flank pain suggests a kidney stone, more common in the Florida heat, as our kidney stone prevention guide explains. In men, prostate enlargement and prostatitis are common sources, but they are accepted as the explanation only after the bladder has been examined. Simple kidney cysts found on imaging almost never bleed and rarely need follow-up.
When nothing is found
A complete evaluation with no cause is the most common outcome and is reassuring. A urine test and blood pressure check yearly for a few years catches the small number of conditions that declare themselves later, and new visible blood at any point restarts the evaluation. Our genito-urinary team coordinates imaging and urology referral. The NIDDK and MedlinePlus publish patient guidance on hematuria and its evaluation.
If blood was found in your urine, even once, and the evaluation was never finished, schedule a visit.