Blood in Urine (Haematuria) — Causes & When to See a Doctor — Causes, Diagnosis & When to See a Doctor | MyMedicPlus

Blood in urine, known medically as haematuria, refers to the presence of red blood cells in the urine. It can be gross (macroscopic) — visible to the naked eye, causing urine to appear pink, red, or brown — or microscopic, detectable only by urinalysis or urine microscopy, defined as more than 3 red blood cells per high-power field. Gross haematuria is alarming and will nearly always prompt the patient to seek medical attention, yet surprisingly only 1–2 mL of blood per litre of urine is sufficient to produce visible discolouration. Microscopic haematuria is often discovered incidentally on routine health screening. While haematuria can arise from entirely benign causes such as strenuous exercise or urinary tract infection, it can also be the first and only warning sign of a serious urological malignancy — particularly bladder cancer. This is why even a single episode of visible haematuria in an adult, regardless of age, must be formally evaluated. The urinary tract — comprising the kidneys, ureters, bladder, urethra, and prostate in men — is extensive, and haematuria can originate at any level within this system. Accurate localisation of the bleeding source is a key goal of clinical assessment.

Urinary tract infection (UTI) is the most common cause of haematuria in young women, typically accompanied by burning on urination, frequency, and urgency. Kidney stones cause haematuria from the abrasive passage of calculi through the urinary collecting system, often producing severe colicky flank pain radiating to the groin. Bladder cancer is the most important diagnosis to exclude in adults over 40 — particularly men — with painless visible haematuria, and is the fourth most common cancer in men. Kidney (renal cell) carcinoma may present with the classic triad of haematuria, loin pain, and a palpable flank mass. Glomerulonephritis — inflammation of the kidney's filtering units — causes microscopic or gross haematuria with proteinuria, oedema, and hypertension. Benign prostatic hyperplasia (BPH) in older men can cause haematuria through distended prostatic veins. Blood-thinning medications including warfarin, rivaroxaban, apixaban, and antiplatelet agents can unmask previously subclinical haematuria. Trauma to the urinary tract from blunt abdominal injury, catheterisation, or urological procedures is another recognised cause. Strenuous endurance exercise (runner's haematuria or march haematuria) produces transient benign haematuria from bladder wall trauma.

Certain features of haematuria indicate a serious or potentially life-threatening condition requiring urgent evaluation. Seek same-day medical attention for visible blood in urine accompanied by fever above 38°C and flank pain — this combination suggests pyelonephritis (kidney infection) which can progress to sepsis if untreated. Seek emergency care if haematuria is accompanied by the passage of blood clots in the urine, as clots can cause obstructive urinary retention. Any haematuria with signs of urinary obstruction — inability to urinate despite urgency — requires emergency catheterisation. Haematuria in a person with known or suspected kidney disease, or associated with a rising creatinine (sign of deteriorating kidney function), requires urgent nephrology review. In adults over 40, particularly men with a smoking history, any episode of painless visible haematuria must be referred urgently for cystoscopy and upper urinary tract imaging to exclude bladder or kidney cancer, even if initial investigations are normal. Haematuria combined with proteinuria on urinalysis and elevated blood pressure suggests glomerular disease and needs nephrology input.

Urinalysis is the first step and confirms the presence of blood, simultaneously screening for infection (white cells, nitrites, protein), glucose, and pH. A positive dipstick for blood should be confirmed by urine microscopy, which can distinguish true haematuria (red blood cells) from haemoglobinuria or myoglobinuria. Urine culture identifies the causative organism if infection is present. Midstream urine should be sent before starting antibiotics. Blood tests assess kidney function (creatinine, eGFR), full blood count, clotting studies, and PSA in men over 50. Renal ultrasound is the safest first-line imaging for the kidneys and bladder, identifying hydronephrosis, stones, and renal masses. CT urogram — a contrast-enhanced CT of the kidneys, ureters, and bladder — provides the most complete upper tract assessment and is the gold standard for haematuria workup in adults over 40. Cystoscopy, performed by a urologist under local or general anaesthesia, directly visualises the entire bladder mucosa and is mandatory in the haematuria workup for adults over 40 or those with risk factors for bladder cancer. Urine cytology detects malignant cells shed from urothelial tumours.

Treatment of haematuria is directed entirely at the identified underlying cause, and the approach varies substantially across the range of possible diagnoses. Uncomplicated UTI is treated with a 3–7 day course of antibiotics targeted to the isolated organism — trimethoprim, nitrofurantoin, and fosfomycin are commonly used first-line agents. Small kidney stones (under 5 mm) usually pass spontaneously with adequate hydration (at least 2–3 litres daily), analgesics (NSAIDs, opioids for severe pain), and alpha-blockers to relax the ureter. Larger stones require urological intervention — shockwave lithotripsy (SWL), ureteroscopy with laser fragmentation, or percutaneous nephrolithotomy for very large stones. Bladder cancer is managed based on stage and grade: non-muscle-invasive bladder cancer is resected transurethrally (TURBT) and may require intravesical BCG immunotherapy to reduce recurrence; muscle-invasive disease requires radical cystectomy with urinary diversion or radical radiotherapy. Glomerulonephritis is managed by a nephrologist and may require immunosuppressive therapy with corticosteroids, mycophenolate, or cyclophosphamide depending on the underlying aetiology. Anticoagulation-related haematuria requires review and dose optimisation rather than automatic cessation of anticoagulation.

Adequate hydration is the cornerstone of urinary tract health — drinking at least 2 litres of water daily dilutes the urine, flushes bacteria, reduces crystal supersaturation that leads to kidney stones, and reduces the concentration of potential carcinogens in contact with the bladder wall. Smoking cessation is critically important: cigarette smoking is the single most significant modifiable risk factor for bladder cancer, responsible for approximately 50% of cases, as carcinogens from tobacco are excreted in concentrated form in urine. Maintain good urogenital hygiene to reduce the risk of UTIs — in women, wiping front-to-back, urinating after sexual intercourse, and staying well hydrated all reduce UTI risk. For those prone to calcium oxalate kidney stones, reduce dietary oxalate (spinach, nuts, chocolate), increase dietary calcium from food sources rather than supplements, and reduce animal protein and sodium intake. Blood pressure control protects long-term kidney function and reduces the risk of glomerular disease. Have annual health checks including urinalysis if you have risk factors for bladder or kidney disease.

Any single episode of visible blood in the urine in an adult — even if it occurs only once and resolves spontaneously — warrants prompt medical evaluation within 24–48 hours. Do not assume a single episode is harmless or caused simply by dietary factors such as beetroot consumption (which produces harmless pink discolouration but can be confirmed by urinalysis showing no actual red blood cells). Seek emergency care for haematuria accompanied by fever and rigors (possible urosepsis), passage of blood clots causing pain or urinary obstruction, haematuria after significant abdominal trauma, or haematuria with acute deterioration in kidney function. Microscopic haematuria detected incidentally on a routine urine test also requires follow-up with your GP, particularly if persistent on repeat testing. Adults over 40 with haematuria should be referred urgently to a urology outpatient clinic for full haematuria workup including cystoscopy and upper tract imaging. Never dismiss haematuria as a minor finding without appropriate investigation.