In short: Blood in your urine (haematuria) should always be checked, even if it happens only once and even if it is painless. Most causes, such as urine infections and kidney stones, are not serious, but visible blood can occasionally be an early sign of bladder or kidney cancer. Ask for a prompt (urgent) GP appointment, and if you cannot get one quickly, call NHS 111.

This guide, written by a Ready Health prescribing pharmacist in Standish, Wigan, explains the common causes, what doctors look for and what to expect when you are assessed.

What is haematuria?

Haematuria means blood in the urine. There are two types:

Visible haematuria: you can see it. Urine may look pink, red, brown or cola-coloured, or you may pass small clots.
Non-visible haematuria: blood is found only on a urine dipstick or laboratory test, often during a routine check.

Is blood in urine serious?

Often it is not, but it should never be ignored. Because a small proportion of cases are caused by cancer of the bladder or kidney, UK guidance treats unexplained visible blood in the urine as a symptom that needs prompt assessment. Do not wait to see whether it happens again, and do not assume it is harmless because it stops.

What are the common causes of blood in urine?

Urinary tract infection (UTI): often with burning when passing urine, needing to go more often, cloudy or smelly urine, or a high temperature.
Kidney or bladder stones: often with severe pain in the side, back or groin that comes and goes, and feeling sick.
Enlarged prostate: in men, usually over 50, with a weak flow, difficulty starting, or needing to pass urine more often, including at night.
Kidney inflammation (glomerulonephritis) and other kidney conditions.
Injury or, occasionally, very strenuous exercise.
Cancer of the bladder, kidney or prostate: less common, and more likely with increasing age and in people who smoke or have smoked.

Could it be something that only looks like blood?

Yes. Beetroot, blackberries and some food dyes can turn urine pink or red, and some medicines (for example rifampicin or nitrofurantoin) can colour urine red, orange or brown. Blood from a period, vaginal bleeding or bleeding from the bottom can also be mistaken for blood in the urine. If you are not sure, get it checked rather than assuming it is harmless.

When is an urgent referral recommended?

The NICE guideline on suspected cancer (NG12) advises GPs to refer people using a suspected cancer pathway (usually seen within two weeks) if they are:

aged 45 or over with unexplained visible blood in the urine and no urine infection, or
aged 45 or over with visible blood in the urine that continues or comes back after a urine infection has been successfully treated, or
aged 60 or over with unexplained non-visible blood in the urine together with pain when passing urine or a raised white cell count on a blood test.

Being under 45 does not mean blood in the urine can be ignored. Your GP will still examine you and arrange tests, and may refer you to a urology or kidney specialist depending on the findings.

When should you get help straight away?

Ask for an urgent GP appointment for any blood in your urine.
Call NHS 111 if you cannot get a GP appointment quickly.
Go to A&E or call 999 if you cannot pass urine at all, you are passing large clots, you have severe pain, or you feel very unwell with a high temperature and pain in your back or side.

What tests might you need?

A urine dipstick and a urine sample sent to the laboratory to check for infection
Blood tests, including kidney function and a full blood count
Blood pressure measurement and a physical examination
Specialist investigations if needed, such as an ultrasound or CT scan of the urinary tract and a cystoscopy (a camera test to look inside the bladder)

Frequently asked questions

I only saw blood once and it has stopped. Do I still need to be seen?

Yes. A single episode of visible blood can still be significant, so book a prompt GP appointment.

Can a urine infection cause blood in urine?

Yes, UTIs are a common cause. If the blood persists or returns after the infection is treated, you should be reassessed.

I take blood thinners. Is that why I have blood in my urine?

Anticoagulants can make bleeding more likely, but they do not explain haematuria on their own. You still need to be assessed for an underlying cause. Do not stop any prescribed medicine without advice.

Can I have a private assessment?

Yes, but please do not let it delay you seeing your NHS GP. A private clinician can assess you and arrange tests, and should share findings with your GP so that any NHS suspected cancer referral is not held up.

Key takeaways

All blood in the urine needs checking, even if painless or only seen once.
Common causes include UTIs, stones and prostate enlargement.
NICE recommends a suspected cancer referral for unexplained visible haematuria in people aged 45 and over.
Seek emergency help if you cannot pass urine or are passing large clots.

Sources and further reading

Last reviewed: October 2026 by Shamir Patel, Independent Prescribing Pharmacist, Ready Health. This article is general information and does not replace advice from your own clinician.

Your NHS GP is the first port of call for blood in the urine. If you would also like a private appointment for an assessment or tests, see our private GP appointments in Standish, Wigan. We will share results with your GP with your consent.

Blood in Urine (Haematuria): Causes and When to See a GP