When to see a vet urgently
A sudden reduction in urination needs prompt assessment. Go to an emergency vet immediately if:
- your cat repeatedly strains but produces no urine or only drops;
- difficulty urinating is accompanied by vomiting, marked lethargy or refusal to eat;
- your cat seems very painful, is unsteady or their general condition collapses;
- urine output decreases after possible poisoning or a serious injury.
Do not wait until urination stops completely. You can find a vet near you for help accessing care.
Overview
Normally, a cat produces a moderate amount of urine reflecting the body's fluid balance. With oliguria, urine production falls markedly: little urine is passed even though the cat drinks enough. Unlike anuria, the complete absence of urine, oliguria means that urine production continues but is severely reduced.
In cats, the condition is often accompanied by other symptoms: apathy, vomiting and behavioural changes.
Urine output is assessed in relation to your cat's size and fluid balance. Drinking what seems an adequate amount does not confirm normal circulation or kidney function. Equally, drinking little from a bowl does not alone prove dehydration, because wet food provides water. Oliguria can also result from a fluid deficit, rather than occurring only when water intake is definitely adequate.
Urine formation in the kidneys and its passage from the bladder are different processes. A small puddle or small litter clumps at home cannot tell you which stage is affected. Frequent visits may mean small, painful amounts of urine, whereas true oliguria means a low total volume. These situations cannot reliably be distinguished by the number of visits alone.
Causes
Renal causes, affecting the kidneys themselves:
- acute kidney failure due to impaired circulation, poisons or infections;
- severe damage to the renal tubules.
Postrenal causes, involving obstruction after the kidneys:
- urethral blockage caused by a stone, mucus or a plug;
- tumours of the bladder or urethra;
- urethral spasm.
Prerenal causes, involving reduced blood flow to the kidneys:
- dehydration from vomiting, diarrhoea or blood loss;
- shock or collapse;
- heart failure and circulatory failure.
In a prerenal problem, too little blood passes through the kidneys. Function may recover when circulation is restored, but a prolonged disturbance can damage kidney tissue itself. More than one mechanism can therefore affect the same cat. Existing chronic kidney disease does not rule out additional acute injury either.
An obstruction can occur not only in the urethra but higher up, in a ureter, which carries urine from a kidney to the bladder. This may not cause the same bladder distension as a urethral blockage. Investigations therefore assess the whole urinary tract when necessary, rather than the bladder alone.
Risk factors
- male cats with urinary stones;
- cats with access to poisonous plants or medicines;
- cats with chronic kidney disease;
- cats following serious injuries or surgery;
- older cats with cardiovascular disease.
The risk of urethral blockage in males is not limited to stones: plugs and other urethral changes can also obstruct urine flow. Reduced urination in a female cat should not be considered harmless, however. Poisoning, kidney damage and upper urinary tract problems are possible regardless of sex.
After serious illness or surgery, monitoring considers circulation, fluid balance and the medicines used. Knowing that a procedure has taken place does not prove kidney damage, but helps your vet target the investigations.
Typical symptoms
- little urine despite normal drinking;
- straining to urinate, particularly in males with a blockage;
- behavioural changes, such as restlessness or apathy;
- lethargy and refusal to eat;
- vomiting and an ammonia smell on the breath in kidney failure;
- pain when urinating with an obstruction.
Straining due to a blockage can be mistaken for constipation. Your cat may repeatedly visit the tray, lick the genital area or cry while trying to urinate. Others hide away and become quiet. Passing drops does not confirm that the bladder is emptying.
Tell the vet when you last definitely saw normal urination, whether litter clumps have changed size and whether there may be blood in the urine. In a multi-cat household, it is not always clear which cat has used the tray, and an outdoor cat's urination may be difficult to observe. State this uncertainty openly; do not delay treatment to obtain a complete record at home.
Complications and consequences
- rapid accumulation of nitrogenous waste and toxic effects;
- electrolyte disturbances, including high potassium leading to abnormal heart rhythms and seizures;
- fluid accumulation in the lungs and brain in severe kidney failure;
- death without treatment.
Potassium accumulation is particularly dangerous for heart function. Seizures can also result from other disturbances associated with severe kidney disease, so their cause cannot be inferred from urine output alone. Excessive fluid therapy can also cause life-threatening fluid overload, especially if no urine is being produced. This is one reason to monitor your cat's condition and fluid elimination closely during treatment.
Diagnosis at the vet
- urinalysis, including specific gravity, protein, blood and casts;
- blood biochemistry, including creatinine, urea and electrolytes;
- kidney and bladder ultrasound to look for stones, tumours or obstruction;
- X-rays if urinary stones are suspected;
- blood pressure measurement.
What is causing the low urine output?
Your vet assesses general condition, circulation, dehydration and the bladder. A firm, full, painful bladder may suggest a urethral blockage, but a small bladder alone does not establish that the kidneys are healthy. Do not try to feel the bladder forcefully or squeeze it empty at home.
Waste products in the blood indicate impaired function, but raised levels alone do not distinguish dehydration, kidney injury and the effects of an obstruction. Results are compared with urinalysis, imaging and previous readings. Early kidney injury may appear as a change from a previous result even while the value remains within the laboratory reference range.
A urine culture is considered if infection is suspected. Not all urinary symptoms are caused by bacteria, and low urine output alone is not a reason to prescribe antibiotics. Finding crystals does not, on its own, establish the cause of an obstruction either. If your cat is unstable, urgent stabilisation begins before extensive investigations are complete.
Measuring urine production
In hospital, urine output can be measured using a urinary catheter and collection system. Fluids given and other losses, such as vomiting, are recorded at the same time. Changes in weight and repeated examinations help show whether a fluid deficit is being corrected or too much fluid is accumulating. Monitoring litter clumps at home provides useful background information, but cannot replace this measurement.
Treatment
Treatment depends on the cause:
- fluid therapy for dehydration;
- catheterisation and removal of the plug or stone for a urethral blockage;
- intensive fluid therapy and support for electrolyte balance in acute kidney failure;
- treatment of symptoms, including anti-sickness medicines, activated charcoal and pain relief;
- dialysis in severe cases.
Fluid therapy does not mean unlimited flushing
Effective fluid therapy means correcting an identified need and continually adjusting treatment. Once fluid balance has been restored, a patient producing no urine is not automatically given more fluid to force urine production. Heart disease also affects how treatment can be delivered safely. Your vet chooses the fluids and amounts used to support kidney function.
A urethral obstruction is relieved alongside the necessary pain relief and stabilisation. Monitoring potassium and heart rhythm may be urgent even before the blockage is removed. Urine output may be high afterwards, so continued monitoring is also needed.
Activated charcoal is not a general treatment for oliguria. Its potential use relates to a particular poisoning, and it does not bind ethylene glycol effectively, for example. A medicine that increases urine output does not itself guarantee kidney recovery either. Dialysis may be considered for severe fluid or electrolyte disturbances and inadequate urine production.
Recovery and the limits of home care
The prognosis depends on the underlying cause, response to treatment and complications. Persistent oliguria is worrying, but a single high creatinine result does not determine the chance of recovery on its own. Poor appetite and nausea are treated, and nutrition is supported as part of recovery.
At discharge, follow-up appointments and symptoms to monitor are agreed. Keep a record of appetite, general condition and urination. Continued monitoring is needed after acute kidney injury even when your cat seems healthy. If difficulty urinating returns, seek a new assessment: a new episode may have a different cause from the previous one.
Prevention
- Help prevent urinary stones with appropriate feeding and adequate drinking.
- Prevent contact with poisons and poisonous plants.
- Have urinary tract infections treated promptly.
- Treat and monitor chronic kidney and heart disease.
- Arrange regular veterinary check-ups.
Provide fresh water in easily accessible places and consider the water in food. Medication and feeding for a cat with kidney or heart disease are planned individually. Encouraging drinking or changing food cannot unblock the urinary tract or replace investigation of a sudden reduction in urine output.
Important for cat owners
Oliguria is an alarming symptom indicating serious urinary system problems. Remember: a sudden reduction in urine output is a reason to seek veterinary care immediately. Only prompt diagnosis and treatment can save your cat's life.
This article provides general information and does not replace veterinary care. If your cat cannot urinate, contact a vet or emergency vet immediately.
Frequently asked questions
Can the urethra be blocked if drops of urine are coming out?
Yes. Passing drops does not guarantee unobstructed urination or bladder emptying. Repeated unsuccessful straining is an emergency even if a little urine is visible in the tray.
Can I encourage my cat to drink more and monitor them at home?
Water can remain available, but a sudden reduction in urine output needs investigation. Increasing drinking cannot correct every cause, and failure to produce urine carries a risk of fluid accumulation. Do not administer fluid therapy yourself.
Does oliguria mean permanent kidney failure?
Not necessarily. It may be caused by a treatable circulatory problem or obstruction, for example, although severe kidney injury is also possible. Recovery is assessed through investigations and monitoring, rather than the name of the symptom alone.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Renal Dysfunction in Dogs and Cats, Merck Veterinary Manual, accessed 2026-11-05.
- Urethral Obstruction in Small Animals, Merck Veterinary Manual, accessed 2026-11-05.
- 2025 iCatCare consensus guidelines on the diagnosis and management of lower urinary tract diseases in cats, Journal of Feline Medicine and Surgery, accessed 2026-11-05.
- AKI Summary 2026, International Renal Interest Society, accessed 2026-11-05.
- Feline acute kidney injury: 2. Approach to diagnosis, treatment and prognosis, Journal of Feline Medicine and Surgery / PubMed Central, accessed 2026-11-05.
- Hydration, Cornell Feline Health Centre, accessed 2026-11-05.
- Acute Kidney Injury in Cats, VCA Animal Hospitals, accessed 2026-11-05.
- Ethylene Glycol Toxicosis in Animals, Merck Veterinary Manual, accessed 2026-11-05.