Symptom guide
Blood in urine: causes, red flags and when to get it checked
Seeing blood in your urine, or a dipstick showing blood you cannot see, should always be reported to a doctor, even if it happens once and stops. Infection and kidney stones are the commonest causes, but bladder and kidney cancers must be excluded, especially in older adults and smokers.
Last checked: 2026-10-03
Key facts
At a glance.
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Always report
Visible blood in urine should be checked even if it stops, because painless bleeding is the typical sign of bladder cancer.
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Painful vs painless
Pain on passing urine suggests infection; colicky loin pain suggests a stone; painless blood needs cancer excluded.
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Age and risk
People over 45, smokers and those exposed to certain chemicals have higher risk.
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Not always blood
Beetroot, rhubarb and some medicines can colour urine, so a urine test confirms.
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Who to see
GP urgently; urology for cystoscopy and imaging.
What this symptom usually means
Blood can enter urine anywhere between the kidney and the urethra. The pattern, including pain, timing during urination and clots, helps point to the source. Because some of the most important causes are painless, doctors do not assume it is benign.
Possible causes, from most to least common
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Urinary tract infection: pain or burning when passing urine, frequency, urgency and cloudy or smelly urine.
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Kidney or ureteric stones: severe colicky pain from loin to groin, nausea and visible blood.
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Enlarged prostate (BPH) in men: weak stream, frequency and occasional bleeding.
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Vigorous exercise, injury or recent catheter or procedure.
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Kidney diseases such as glomerulonephritis, with brown cola-coloured urine and swelling.
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Medicines: anticoagulants, aspirin and some antibiotics can unmask or cause bleeding.
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Bladder cancer: painless visible blood, often intermittent, with smoking and age as risk factors.
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Kidney cancer, prostate cancer and polycystic kidney disease, which are less common but important.
Features that point to something more serious
Visible blood without pain or infection, age over 45 (particularly over 60), smoking history, exposure to dyes or chemicals, passing clots, persistent blood after antibiotics, loin pain with fever, weight loss and a family history of kidney or bladder disease warrant specialist assessment.
Red flags: when to seek help
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Call 999 or go to A&E: heavy bleeding with clots and inability to pass urine, or collapse.
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Same-day GP or NHS 111: blood in urine with fever, severe loin pain or vomiting.
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Urgent GP referral: visible blood in urine without infection, particularly over 45, or blood that persists after infection treatment.
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GP within weeks: non-visible blood found on a dipstick on more than one occasion.
What a doctor will ask and examine
The doctor asks whether blood is visible, timing, clots, pain, urinary symptoms, fever, smoking, work exposures, medicines, family history, recent exercise or injury. They check blood pressure, examine the abdomen and loins and, in men, may examine the prostate.
Tests that are commonly used and why
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Urine dipstick and culture: to identify blood and infection.
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Blood tests: kidney function (eGFR), full blood count, and PSA in men after discussion.
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Ultrasound of kidneys and bladder, or CT urogram: to look for stones, masses and structural problems.
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Flexible cystoscopy: a camera test to look inside the bladder, usually under local anaesthetic.
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Urine cytology and kidney assessment for protein (ACR).
Self-care and the usual route
While waiting for assessment, drink plenty of water, avoid straining and note any clots or pain. If a urine infection is confirmed, complete treatment, then recheck the urine. Do not ignore blood that clears; it still needs checking. Stop smoking to reduce bladder cancer risk.
The NHS route is a GP and urgent urology referral under the suspected cancer pathway where applicable. Private urology offers rapid access to cystoscopy and imaging.
Frequently asked
Questions people ask.
Quick, plain-English answers to the questions we hear most.
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Is blood in urine always cancer?
No. Infection and stones are more common, but cancer must be excluded because early treatment gives better outcomes.
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What if it was only once?
A single episode still needs assessment, since bladder cancer bleeding is often intermittent.
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What is a cystoscopy?
A test using a thin camera passed through the urethra to look inside the bladder, usually under local anaesthetic.
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Can exercise cause blood in urine?
Intense exercise can occasionally cause temporary bleeding, but it should still be checked if it recurs or persists.
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Can food colour urine?
Yes. Beetroot, rhubarb and some medicines can turn urine pink or red. A dipstick confirms whether blood is present.
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What is non-visible haematuria?
Blood found on a urine test that you cannot see, which is also investigated, usually with kidney tests, imaging and sometimes cystoscopy.
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Do blood thinners explain it?
They can increase bleeding, but it should still be investigated rather than assumed to be due to the medicine.
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What can I do to reduce risk?
Stop smoking, drink plenty of fluids, and limit exposure to industrial chemicals where possible.
Where this comes from
Sources and checking.
This guide is for information, not medical advice.
Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.
Published 2026-10-03, next review 2027-10-03.
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NHS: Blood in urine (haematuria) (nhs.uk/conditions/blood-in-urine/)
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NICE guideline NG12: Suspected cancer - recognition and referral
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NHS: Bladder cancer (nhs.uk/conditions/bladder-cancer/)