What causes blood in a cat's urine?

The most common cause in young to middle-aged cats is feline idiopathic cystitis (FIC/FLUTD) — stress-triggered bladder inflammation with no bacterial infection. Other causes include bladder stones (struvite or calcium oxalate), UTI (more common in older cats), urethral obstruction in male cats (emergency), bladder polyps or cancer, kidney disease, coagulopathy, and trauma.

Is a cat straining to urinate an emergency?

Yes — a male cat that is straining repeatedly and producing little or no urine is a life-threatening emergency. Male cats have a very narrow urethra and can develop a complete urethral obstruction from a plug, stone, or spasm. Without treatment within 24–48 hours, the backed-up urine causes severe hyperkalemia (high potassium) and cardiac arrest. Go to the emergency vet immediately — do not wait overnight.

What is FLUTD in cats?

FLUTD (feline lower urinary tract disease) is an umbrella term for conditions causing lower urinary signs — blood in urine, straining, frequent trips to the litter box, urinating outside the box, and sometimes urethral obstruction. In young adult cats without bacteria in the urine, the most common form is feline idiopathic cystitis (FIC) — stress-triggered bladder inflammation. Management focuses on stress reduction, diet change to wet food, and environmental enrichment.

What does blood in cat urine look like?

Owners may notice pink or reddish staining in the litter box, or on surfaces where the cat has squatted outside the box. Some cats have visibly red urine; others have microscopic blood found only on urinalysis. Blood at the end of urination (a few drops after the stream) is common with bladder neck or urethral involvement. The urine may also appear cloudy.

Can stress cause blood in a cat's urine?

Yes — and this is unique to cats compared to dogs. Feline idiopathic cystitis (FIC) is stress-induced bladder inflammation that causes blood, straining, and urinary signs without any bacterial infection. Common triggers: new pet in the household, moving, owner's schedule change, building work, outdoor stressors (other cats seen through windows). Management includes environmental enrichment, Feliway diffusers, and wet food.

Do cats get UTIs causing blood in urine?

Less commonly than dogs. Cats produce highly concentrated urine that naturally resists bacterial growth. UTI as a primary cause of hematuria is most common in older cats (over 10), cats with CKD (dilute urine), diabetic cats, and cats on long-term corticosteroids. In a young adult cat with bloody urine and no other findings, FIC is far more likely than UTI.

What are bladder stones in cats?

Cats develop two main types of bladder stones: struvite (magnesium ammonium phosphate) and calcium oxalate. Struvite stones in cats are often diet-related (high-mineral dry food, concentrated urine) and can sometimes be dissolved with prescription urinary dissolution diets. Calcium oxalate stones cannot dissolve and require surgical removal or laser lithotripsy. Middle-aged to older males are most commonly affected by calcium oxalate.

What is a urethral plug in cats?

A urethral plug is a soft, protein-based mass (containing mucus, crystals, cells, and debris) that lodges in the narrow urethra of male cats, causing obstruction. It is distinct from a hard stone. Plugs are the most common cause of urethral obstruction in male cats. They are removed by flushing or gentle manipulation under anesthesia. Risk factors: dry food diet, low water intake, stress, and FLUTD history.

Can PKD cause blood in a cat's urine?

Polycystic kidney disease (PKD) affects up to 40% of Persian and Exotic Shorthair cats. Kidney cysts can occasionally bleed, causing microscopic hematuria. PKD is diagnosed by ultrasound (cysts visible from 10 months) or genetic DNA test. More often PKD causes kidney enlargement and eventual CKD rather than dramatic hematuria.

How do vets treat blood in cat urine?

Treatment depends on the cause. FIC: stress reduction, wet food diet, pain relief (buprenorphine), environmental enrichment — resolves in 5–7 days in most uncomplicated cases. UTI: antibiotics based on culture. Bladder stones: dissolution diet (struvite) or surgery/lithotripsy (calcium oxalate). Urethral obstruction: emergency catheterization, IV fluids, monitoring for 24–48 hours. Bladder cancer: surgery where feasible, piroxicam as palliative.

Blood in Cat's Urine: Causes, FLUTD & When It's an Emergency

A male cat squatting and straining with little or no urine output has a urethral obstruction — this is fatal within 24–48 hours without treatment. Go to an emergency vet immediately, even at 2am. Signs: straining repeatedly with no output, crying, hiding, licking genitals excessively, distended hard abdomen, vomiting, collapse.

Blood found on your cat's urinalysis?

Upload the full urinalysis to see RBCs, WBCs, crystals, and USG together — the combination tells you whether this is FIC, infection, or something else.

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Blood in a cat's urine ranges from a self-limiting stress response to one of veterinary medicine's true emergencies. The key variable is sex: a male cat straining to urinate is a medical emergency until proven otherwise. A female cat with blood and no straining almost certainly has feline idiopathic cystitis or a UTI — serious but not immediately life-threatening.

First: Is Your Cat Actually Urinating?

Before anything else, answer this question: is urine coming out?

Urine is coming out (even small amounts)

Urgent vet visit today. Blood with straining but some output is likely FIC, infection, or stones. Not an immediate minute-by-minute emergency, but don't wait more than a day.

No urine output (especially male cats)

Emergency vet immediately. Complete urethral obstruction is life-threatening. Kidneys cannot excrete potassium — cardiac arrest can occur within 24–48 hours.

Urethral Obstruction: Why Male Cats Are at Risk

Male cats have an anatomically narrow urethra that tapers to a very small diameter at the tip. This makes them uniquely vulnerable to blockage that female cats — with their shorter, wider urethra — almost never develop.

The blockage is usually a urethral plug — a soft mass of mucus, inflammatory cells, proteins, and crystals that accumulates and lodges at the penile urethra. Less commonly, a hard stone causes the obstruction. Urethral spasm without a physical plug also occurs.

What happens when a male cat is blocked

Hour 0–12:Straining, blood in urine, discomfort. Bladder fills and becomes painful.

Hour 12–24:Bladder distends severely. Kidney waste products build in bloodstream. Potassium rises (hyperkalemia).

Hour 24–48:Vomiting, profound lethargy, collapse. Hyperkalemia causes life-threatening arrhythmia.

Hour 48+:Cardiac arrest. Fatal without emergency intervention.

Treatment requires emergency catheterization under anesthesia to relieve the obstruction, flush the bladder, and correct the dangerous electrolyte imbalances with IV fluids. Most cats recover fully with prompt treatment. See cat not peeing emergency guide.

After a first obstruction, dietary changes (wet food, prescription urinary diet) and stress management dramatically reduce the risk of recurrence. Perineal urethrostomy (PU surgery) — widening the urethral opening surgically — is recommended for cats with multiple obstructions.

Understand Your Cat's Urinary Results

Upload your cat's urinalysis to VetLens — see RBCs, crystals, USG, and protein together to understand the full picture.

Analyze My Cat's Results

Most Common Causes of Blood in Cat Urine

• Feline idiopathic cystitis (FIC/FLUTD) — stress-triggered bladder inflammation with no bacterial infection; accounts for ~60–70% of lower urinary tract signs in cats under 10. Classic profile: indoor, overweight, dry-food-only diet, recent stress trigger (new pet, moved furniture, owner travel). Urine is highly concentrated (USG >1.040). Resolves in 5–7 days but recurs without management. Treatment: wet food, stress reduction, Feliway diffuser, buprenorphine for acute pain. See FLUTD in cats.
• Bladder stones (struvite or calcium oxalate) — cat struvite stones are usually diet-related (supersaturated urine from dry food) and can dissolve with prescription dissolution diet. Calcium oxalate stones, most common in middle-aged to older males, cannot dissolve — require surgery or laser lithotripsy.
• UTI — uncommon in young healthy cats because concentrated urine inhibits bacterial growth. Becomes much more common in cats with CKD (dilute urine), diabetes, hyperthyroidism, or immunosuppression. Subclinical UTI in older cats is found only on culture. Always run a urine culture. See UTI in cats.
• Polycystic kidney disease (PKD) — affects up to 40% of Persians and Exotic Shorthairs; cysts occasionally bleed, causing microscopic hematuria. More commonly PKD presents as kidney enlargement and CKD rather than dramatic blood. Diagnosed by ultrasound from 10 months or PKD1 genetic test.
• CKD and upper urinary tract bleeding — advanced CKD causes microscopic hematuria from damaged tubules and glomeruli. Calcium oxalate nephroliths are common in cats and may bleed; hematuria from the kidneys appears uniformly throughout the entire stream. See CKD in cats.
• Bladder cancer / polyps — TCC is less common in cats than dogs; bladder polyps (benign) are more frequent and cause similar signs. Persistent hematuria that doesn't respond to treatment warrants ultrasound regardless of age.
• Anticoagulant rodenticide poisoning — secondary poisoning from eating a poisoned rodent does occur in cats. Hematuria alongside bleeding from gums, nose, or skin bruising, or breathing difficulty from thoracic hemorrhage, requires emergency coagulation testing and vitamin K1.

FIC vs UTI vs Stones: How to Tell Them Apart

FIC (idiopathic cystitis)

Profile: Young, indoor, stressed, dry food diet

USG: High (>1.040)

Bacteria: None

Crystals: Sometimes

Resolution: 5–7 days, recurs

UTI

Profile: Older cat, CKD, diabetic, immunosuppressed

USG: Low (<1.035)

Bacteria: Yes (culture)

Crystals: Sometimes

Resolution: With antibiotics

Bladder stones

Profile: Any age, recurrent signs

USG: Variable

Bacteria: Maybe (secondary)

Crystals: Often

Resolution: Diet or surgery

Condition	Typical Patient	USG	Bacteria	Resolution
FIC	Young, indoor, stressed, dry food	High (>1.040)	None	5–7 days, recurs without management
UTI	Older cat, CKD, diabetic	Low (<1.035)	Yes (culture)	With antibiotics
Bladder stones	Any age, recurrent signs	Variable	Sometimes (secondary)	Dissolution diet or surgery

FIC cats have highly concentrated urine (USG >1.040) — the opposite of what many people expect. Concentrated urine irritates the already-inflamed bladder and promotes crystal formation. Switching to wet food dilutes the urine, which is one of the most effective long-term FIC management strategies. A cat with bloody urine and dilute urine (USG <1.025) is more likely to have UTI or CKD than FIC.

What Your Vet Will Do

Palpate the bladder — in male cats, a large, firm, painful bladder means obstruction; relief of the obstruction is the immediate priority

Urinalysis with sediment — RBCs, WBCs, bacteria, crystals (type guides stone management), casts

Urine culture — to distinguish UTI from FIC; essential in older cats and cats with dilute urine

Abdominal X-ray and/or ultrasound — stones (X-ray for radio-opaque; ultrasound for radiolucent and bladder wall assessment), kidney cysts, masses

Bloodwork — in blocked cats (potassium, BUN, creatinine are critical); in older cats with bloody urine (T4, kidney panel, glucose)

Blood pressure — in older cats; hypertension worsens renal hematuria and is associated with CKD

Key Takeaway

Blood in cat urine is almost always lower urinary tract disease — FIC or UTI — and is very treatable. The exception that changes everything is a male cat that cannot urinate.

Know the difference: a cat that is straining but producing some urine needs a vet today. A cat that is straining and producing nothing needs an emergency vet right now. Check the litter box carefully before deciding.

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Upload your cat's urinalysis to VetLens and instantly see:

✓ RBC, WBC, and crystal findings interpreted together
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✓ What to ask your vet about diet and stress management

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Frequently Asked Questions

My cat had blood in urine once and it stopped — should I still go to the vet?

Yes. A single episode that resolved may be FIC (self-limiting in 5–7 days) but should be evaluated to rule out stones, infection, or structural abnormality. If it happens again, imaging is needed — recurrent FIC vs stones requires different management.

My female cat has blood in urine but seems fine — how urgent is it?

A female cat straining but producing some urine, or with blood but no straining, is not a minute-by-minute emergency. But it should be seen within 24 hours. Female cats don't obstruct the way males do, but they still need a urinalysis to distinguish FIC from UTI from stones.

How do I prevent my cat from getting blocked again?

The three most evidence-based interventions after a first obstruction: (1) switch entirely to wet food — this single change reduces recurrence risk significantly by diluting urine; (2) prescription urinary diet (e.g. Hills c/d, Royal Canin Urinary SO); (3) stress reduction — identify and remove triggers, add Feliway diffusers, increase litter boxes (one per cat plus one). Cats with multiple obstructions are candidates for perineal urethrostomy surgery.

Can dry food cause blood in cat urine?

Indirectly. Dry food leads to low water intake and highly concentrated urine, which is a major risk factor for both FIC and crystal/stone formation. This is why wet food — or adding water to dry food — is one of the most recommended preventive measures for cats with recurrent hematuria or FLUTD.

What does brown urine mean in a cat?

Brown or very dark urine in cats can indicate: old blood from kidney or upper urinary tract (the blood has broken down), hemoglobinuria from red blood cell destruction (hemolytic anemia — the plasma would also be pink), or myoglobinuria from severe muscle damage (rare in cats). A sediment exam distinguishes intact RBCs from hemoglobin/myoglobin. Very dark brown or black urine is an emergency.

Blood in a Cat's Urine: Causes, FLUTD & When It's an Emergency