Blood in Urine (Haematuria): Causes and When to Act
Updated April 2026
Visible blood in urine always needs assessment
Any visible blood in urine not explained by recent beetroot or berries should be assessed by a GP. In the UK, over-45s with painless visible blood qualify for an urgent two-week cancer referral (NICE NG12). This does not mean cancer is likely - UTI and kidney stones are far more common - but it must be ruled out.
Gross vs Microscopic Haematuria
Haematuria is the medical term for blood in urine. It occurs in two forms with different clinical implications:
Gross haematuria
Visible blood: urine appears pink, red, or brown. Even a small amount of blood (1ml in 1L of urine) can produce visible colour change. Always requires assessment. Multiple possible causes, most benign, but bladder cancer must be excluded in at-risk individuals.
Microscopic haematuria
Blood cells present but urine appears normal. Detected on dipstick or urine microscopy. Often found incidentally on routine testing. Requires assessment especially in at-risk groups. Less urgency than gross haematuria in isolation.
Common Causes of Blood in Urine
1. UTI (most common in women)
Bladder infection causes inflammation, and blood vessels in the bladder lining can bleed into the urine. Usually accompanied by burning, frequency, and urgency.
2. Kidney stones
Stones moving through the ureter scratch tissue and cause significant bleeding. Almost always accompanied by severe colicky flank pain. Stones can be silent until they move.
3. Benign prostatic hyperplasia (BPH) or prostatitis (men)
An enlarged prostate or inflamed prostate can cause blood in urine. Accompanied by urinary hesitancy, weak stream, frequency.
4. Glomerulonephritis
Kidney inflammation allowing blood cells to leak through. Can follow a throat infection (post-streptococcal GN). Also causes protein loss, swelling, and high blood pressure.
5. Bladder cancer
Painless visible haematuria is the most common presenting symptom. More common in over-65s, men, smokers, and those with occupational exposure to aromatic amines. UK NICE guidelines specify urgent two-week referral for over-45s with unexplained visible haematuria.
6. Vigorous exercise (athletic haematuria)
Running-related impact trauma to the bladder walls can cause transient haematuria. Typically clears within 24-48 hours of rest. Persistent haematuria after exercise needs evaluation.
7. Anticoagulant medications
Warfarin, apixaban, and rivaroxaban at therapeutic or supra-therapeutic levels can cause haematuria. Requires dose check and clinical assessment.
Differentiating Blood from Beetroot and Menstruation
Two common false positives for haematuria:
- -Beeturia: Ate beetroot in the last 24 hours and urine turned pink or red? Stop eating beetroot and check again - if it clears within 48 hours, it was beeturia. A urine dipstick will be negative for red blood cells (beetroot pigment does not trigger the haem-detecting strip).
- -Menstrual contamination: Blood from menstruation can contaminate a urine sample, causing a positive dipstick and visible tint. Test mid-stream, or collect a sample outside of menstruation, for a clean result. If blood is visible at non-menstrual times, treat as haematuria.
When to Seek Care
Emergency: Blood plus severe flank pain; blood plus blood clots; blood plus severe vomiting or fever; blood after crush injury.
GP same day: Any visible blood not explained by beetroot/berries. UK over-45s: mention two-week urgent referral pathway.
Monitor: Pink urine after confirmed beetroot intake, no other symptoms - stop beetroot and recheck in 24-48 hours. If clears, was beeturia.
Sources: NHS Blood in Urine; NICE NG12 cancer referral guidelines; Cleveland Clinic; American Urological Association haematuria guidelines.