The short answer
Blood in the urine is usually caused by urinary infections, kidney stones, or an enlarged prostate — not cancer. But because it can be an early sign of bladder or kidney cancer, any blood in the urine, even once, should be checked by a doctor.
Most blood in the urine comes from infections, stones, or an enlarged prostate.
Because it can be an early sign of bladder or kidney cancer, it should always be checked.
Blood may be visible or found only on a urine test.
Even a single episode of visible blood in the urine is worth a doctor's review.
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The full explanation.
The short answer
Usually not. Urinary tract infections and kidney stones cause most blood in the urine. It can also be the most common symptom of bladder cancer, so it always deserves a doctor's evaluation, even if it happens only once.
What the blood can look like
Blood in the urine can be easy to see. It can turn urine pink, red, or tea-colored. It can also be invisible, in such a small amount that only a urine test finds it. You may see blood once, then not see it again for a while. That pattern can be misleading. It does not mean the problem went away. It means the bleeding may be coming and going. Any visible blood, even a single episode, should be checked. Do not dismiss it just because it did not happen again right away.
Why bladder and kidney cancer cause this
A tumor in the bladder or kidney has a fragile surface. It can bleed into the urine as it grows. This bleeding is often painless. That can make it easy to brush off, especially when it does not happen every time you urinate. Other symptoms can include frequent urination, pain or burning when urinating, or feeling like you need to go even when your bladder is not full. These other symptoms can also come from far more common conditions.
Far more common causes
Urinary tract infections are one of the most common causes of blood in the urine, especially in women, and usually come with burning or urgency. Kidney stones can cause blood in the urine along with sharp pain. Vigorous exercise can occasionally cause temporary blood in the urine in otherwise healthy people. Certain medicines and an enlarged prostate in men can also be responsible.
What a doctor checks next
Your doctor asks about the color and timing of the blood. They ask whether you have pain or other urinary symptoms. A urinalysis checks the color of the urine. It looks for red blood cells, white blood cells, and signs of infection. If infection is ruled out, or the blood continues, imaging is often next. A CT scan or ultrasound can look at the kidneys and surrounding structures. A cystoscopy is often used too. This is a thin scope that looks directly inside the bladder. It can find bladder tumors that imaging alone might miss. If anything abnormal is found, a biopsy confirms the diagnosis. NCI's guide to pathology reports says the result normally goes to your doctor within 10 days.
What a clean infection test does not rule out
A urine test that is clear of infection does not rule out every cause of blood in the urine. If blood in your urine continues, or you were treated for an infection but the blood does not fully clear, ask about a cystoscopy rather than assuming the infection explained everything.
When to get help sooner
- Call 911 or go to an emergency department if you cannot pass urine at all, or you are passing clots along with heavy bleeding.
- Call your care team the same day if blood in the urine comes with a fever, chills, or severe pain in your back or side.
- Call your care team within a day or two if you see visible blood in your urine even once, and even if it clears up on its own.
What to ask your doctor
- What could be causing this blood in my urine?
- Do I need a cystoscopy or imaging, or can we start with a urine test?
- Could this be an infection, stones, or something that needs closer follow-up?
- What symptoms should send me to urgent care?
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Common questions
Does blood in the urine mean cancer?
Usually not. It is most often caused by infections, stones, or an enlarged prostate. But because it can be an early sign of bladder or kidney cancer, it should always be checked.
It happened once and stopped — do I still need to get it checked?
Yes. Even a single episode of visible blood in the urine is worth a doctor's review, because bladder and kidney cancers can cause bleeding that comes and goes.
What are the common non-cancer causes?
Urinary tract infections, kidney or bladder stones, an enlarged prostate, and vigorous exercise are common causes. Some foods and medicines can also color the urine.
Is painless blood more concerning?
Painless visible blood in the urine is a classic reason to get checked, but any blood in the urine is worth reviewing regardless of pain.
Questions to ask your doctor
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Sources last checked: 2026-08-13 what this meansLast updated: 2026-08-17Next planned review: 2027-07-12
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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