Chronic kidney disease is common in older cats, but increased thirst, weight loss, vomiting, or appetite changes can also have other causes. Blood and urine testing help distinguish chronic disease from acute kidney injury and guide an individual treatment plan.
Written or medically reviewed by Dr. Susset Diaz Castillo, DVM, PhD. Last reviewed: 2026-08-27.
Quick Summary: Chronic kidney disease is common in older cats, but increased thirst, weight loss, vomiting, or appetite changes can also have other causes. Blood and urine testing help distinguish chronic disease from acute kidney injury and guide an individual treatment plan.
Chronic kidney disease (CKD) is a persistent loss of kidney function that usually develops over time. It becomes more common as cats age, but age alone does not establish a diagnosis and published prevalence estimates vary with the population and testing criteria.
Acute kidney injury develops over hours to days and may follow toxin exposure, infection, urinary obstruction, reduced blood flow, or another illness. Acute injury can occur in a cat with previously normal kidneys or on top of CKD. Some causes may improve with prompt treatment, so a sudden change should not be assumed to be routine progression of chronic disease.
These signs are not specific to kidney disease. Diabetes, hyperthyroidism, urinary disease, gastrointestinal disease, medication effects, and other conditions can look similar.
Keep fresh water freely available unless a veterinarian is directly supervising a specific procedure. Cats with kidney disease may be unable to conserve water normally, and restricting access can worsen dehydration and electrolyte abnormalities. Water fountains, wet food, or adding water to food may help some cats, but a sudden or sustained change in thirst still needs evaluation.
Go to an emergency veterinary hospital for suspected lily, antifreeze, human medication, or other toxin exposure; repeated vomiting with inability to keep water down; collapse; seizures; severe weakness; breathing difficulty; marked dehydration; or straining with little or no urine. Do not wait for a house-call appointment when signs are severe or rapidly worsening.
Evaluation generally combines the history and physical examination with bloodwork and urinalysis. Creatinine, blood urea nitrogen, SDMA, electrolytes, urine concentration, urine protein, blood pressure, and trends over time may all contribute. No single value should be interpreted in isolation.
Urine culture, thyroid testing, radiographs, or ultrasound may be recommended depending on the findings. Ultrasound can assess kidney size and structure and may identify stones, obstruction, cysts, or other abnormalities, but imaging alone does not determine kidney function or prove that a change is chronic.
After CKD is diagnosed and the patient is stable, veterinarians may use International Renal Interest Society staging and substaging to help plan treatment and monitoring.
There is no single plan for every cat. Depending on disease stage, appetite, hydration, blood pressure, urine protein, phosphorus, potassium, and other illnesses, a veterinarian may recommend:
Maintaining adequate calorie intake matters. Do not force-feed, start fluids, add phosphorus binders or supplements, or change prescription medication without veterinary direction. Fluids are not appropriate at every stage and can be harmful in some patients, including cats with certain heart conditions or fluid overload.
VestaSoul — My Vet At Home® is a mobile veterinary house-call practice serving select areas of Miami-Dade County and select areas of Broward County. When an appointment is available and the cat is stable, the team may be able to perform an examination, measure blood pressure, and collect selected blood or urine samples at home. A familiar setting may reduce stress for some cats, but it does not guarantee a more accurate result or eliminate the need to repeat an abnormal measurement.
Cats with suspected toxin exposure, urinary obstruction, severe dehydration, uncontrolled vomiting, marked weakness, breathing difficulty, or a need for intravenous therapy, continuous monitoring, advanced imaging, or hospitalization require prompt referral to an appropriate facility.
No. Keep fresh water freely available unless a veterinarian is directly supervising a specific procedure. Restricting water can worsen dehydration or electrolyte abnormalities. Arrange an examination and testing to identify the reason for the change.
Bloodwork is important, but the distinction usually depends on the history, examination, urinalysis, previous results, response to treatment, and sometimes imaging or additional tests. Acute injury can occur on top of chronic disease, and prompt assessment matters when a cat changes suddenly.
No single treatment fits every cat. Therapeutic kidney diets have an important role for many cats with CKD, while fluid plans depend on hydration, disease stage, heart health, and other findings. A veterinarian should tailor the plan and monitor the response.
Dr. Susset Diaz Castillo, DVM, PhD is the veterinarian behind VestaSoul — My Vet At Home®. VestaSoul — My Vet At Home® is a mobile veterinary house-call practice serving select areas of Miami-Dade County and select areas of Broward County. Learn more at Meet the Vet.
This article is for general educational purposes only and is not a substitute for an in-person examination, diagnosis, or treatment by a licensed veterinarian. If your pet is showing severe or rapidly worsening symptoms — such as collapse, difficulty breathing, uncontrolled bleeding, seizures, suspected poisoning, or an inability to urinate — go to the nearest emergency animal hospital immediately. VestaSoul — My Vet At Home® is an appointment-based, non-emergency practice and does not provide emergency or after-hours care.
VestaSoul — My Vet At Home® is a mobile veterinary house-call practice serving select areas of Miami-Dade County and select areas of Broward County.