Updated 7/15/25
Chronic Kidney Disease (CKD)—formerly called Chronic Renal Failure (CRF)—is common in older cats. Natural kidney disease can occur in cats of any age, but it occurs far more frequently in much older cats. CKD can also result from traumatic injury, toxins, medications, infections, or parasites. It is one of the leading causes of death in cats (second only to cancer).
This article is a general overview of a very broad and complicated topic. My goal is to give you enough information to understand the basics of CKD.
Early Signs and Diagnosis
The most noticeable early symptom of CKD is increased thirst and urination. I call this “drink-a-lot, pee-a-lot syndrome.” If you notice your cat drinking or urinating more than usual, have your vet do a blood test and a urinalysis. It’s important to do both tests, as many conditions cause these symptoms.
The kidneys have several functions, but production of urine is their primary duty. They do this by filtering the blood through a system of tiny tubes. Toxins and wastes stay in the tubes and go out with the urine. Water, protein, glucose, and electrolytes get reabsorbed.
In CKD, the kidneys lose their ability to conserve water and concentrate urine. The kidneys have a very large reserve capacity, but over time, cells die and are replaced by scar tissue. Symptoms don’t show until about 75% of kidney tissue is nonfunctional.
Diagnosing CKD
A diagnosis of CKD requires testing of both blood and urine for the presence of:
- Azotemia (high blood levels of the waste products BUN and creatinine), and
Dilute urine, measured by Urine Specific Gravity (USG) of 1.035. In cats, USG is normally about 1.025 for cats eating a high-moisture diet. But the kidneys should be able to adjust and conserve water (increase USG) if azotemia occurs.
If USG is low and azotemia is present, kidney function is likely impaired.
Note: BUN and creatinine levels can be misleading. They may rise with dehydration, high-protein diets, or stress (like a car ride). Elevated BUN by itself does not mean kidney failure. A urinalysis is necessary to confirm a CKD diagnosis.
UP/C, SDMA and IRIS Stages
There are a couple of other common diagnostic items you may hear about.
UP/C is the Urine Protein/Creatinine ratio. This assesses how much protein and creatinine are being lost through the urine. Creatinine is a waste product that is normal in the urine. But the kidneys should be reabsorbing most protein. If there’s a lot of it in the urine, that’s a bad sign. But several conditions can cause protein to spill into the urine. The UP/C helps distinguish between causes. It is also an accurate way to track the progression of disease. It’s interesting information, but not crucial to managing a CKD cat.
SDMA is a blood test that measures a breakdown product of the amino acid arginine. It was supposed to help detect kidney dysfunction before other tests could. This would lead to earlier and better treatment. These hopes remain largely unfulfilled. SDMA by itself doesn’t mean much, especially if other blood tests are normal, or there are no symptoms. It is not accurate enough to use as a monitoring tool.
IRIS (International Renal Interest Society) staging is a concept borrowed from human medicine. Prognosis and treatment of CKD depends on how advanced the disease is. But there are a lot of gray areas among the stages. Stage 1 is where there are no symptoms. In other words, the cat may be normal, or maybe not quite. Stage 2 is the most common diagnostic stage, where signs appear and tests will be abnormal. Stage 2 covers a broad range. Stage 3 is severe CKD, and Stage 4 is end-stage disease.
Causes of CKD
- Vaccination. The feline panleukopenia (FVRCP) vaccine creates antibodies that cross-react with feline kidney cells. This inevitably creates some kidney inflammation. More frequent vaccination is more likely to lead to disease. FVRCP boosters are not needed after first series. It is a very effective vaccine, and the immunity lasts for life. Of course, never vaccinate a cat with CKD for (I don’t recommend any vaccines for cats over 14 due to the risk of adverse effects.)
- Dental Disease. Studies show that dental disease is a major risk factor for kidney problems. Bacteria in the mouth have easy access to the bloodstream. Every bite of food the cat takes releases tens of thousands of bacteria into the blood. As these bacteria float around the body, they get trapped in the small blood vessels and tubules of the kidneys. There they reproduce into huge colonies that. They cause inflammation and scarring that destroy the tissue over time. (Note: Dry food does not clean the teeth or help prevent dental disease.) I’m not going to tell you to brush your cat’s teeth–almost nobody does it consistently, including me. But you *must* tend to your cat’s teeth via annual or semi-annual veterinary visits, and dental cleanings (with or without anesthesia) when needed.
- Dry food: Cats are desert animals and get most of their moisture from prey. Dry food provides only half the water of canned or homemade diets. Cats just don’t drink enough to make up for that. Chronic dehydration from dry food stresses the kidneys. Lower urinary tract issues like FLUTD, crystals, and stones can also play a role in CKD.
- Fish and seafood. A toxin called domoic acid is produced by algae and accumulates in fish and seafood. It causes kidney damage at levels 100x lower than what’s permitted in human food. Pet food may include seafood rejected for human consumption due to high toxin levels. Avoid fish-based diets for cats of all ages, but particularly for CKD cats. [**However, the small amount of fish meal used as flavoring or as a source of Omega-3 fatty acids in many cat foods is probably safe.]
Treatment Overview
CKD is progressive and considered incurable. However, treatment may slow or reverse the disease, at least in early stages.
The main problems caused by CKD are:
- Dehydration
- Toxin build-up in the blood
- Hypertension (high blood pressure)
- Anemia
These and other symptoms like vomiting and poor appetite are all treatable. Track these potential problems with regular bloodwork and blood pressure testing.
Some cats live comfortably for years with proper care; others decline more quickly. Treatments include medications for anemia, high blood pressure, phosphorus control, and potassium supplements.
Diet: The Protein Controversy
Protein restriction is standard in traditional treatment—but it’s controversial for cats.
- High-protein diets do not cause kidney disease in healthy cats.
- Low-protein diets do not prevent kidney disease.
- Protein restriction may help in later stages, but only when BUN levels are high (60–80 mg/dL).
- Too little protein can cause weight loss, harm organs, and worsen the disease.
The worst dietary culprit is phosphorus, which is abundant in meat. Build-up of waste products from protein digestion can also be harmful. Renal diets reduce phosphorus by cutting protein, which is both convenient and inexpensive. They are not appropriate in early stages of disease. Later, they are most useful to manage symptoms. They do not stop or reverse the disease.
Recent research suggests that excessive phosphorus may cause kidney disease even in healthy cats. Many commercial cat foods are extremely high in phosphorus. This not just from meat but also supplements and flavorings added to the food. (See the charts at www.catinfo.org to find foods lower in phosphorus, Aim for a value of 250 mg /100 kcal or less.)
Some helpful tips:
- Feed a high moisture diet like canned food. Dry food just makes dehydration worse.
- Use low-phosphorus protein sources like egg whites or soft cheese.
- Consider adding a phosphate binder to the diet when blood phosphorus increases.
- Choose canned foods lower in phosphorus—look for 300 mg/100 kcal or less (see catinfo.org for charts). No regular canned food will be as low as renal prescription diets, but many foods are far too high.
Important: Many cats dislike renal diets and won’t eat them. If your cat won’t eat it, it’s useless—even harmful. Maintaining weight and hydration is far more important than strict protein control.
Let me say this again, because it is the single most important thing to know about CKD: feed the cat anything she will eat! IF THE CAT WON’T EAT IT, IT WON’T HELP THE CAT! Weight loss is your cat’s worst enemy in this disease; so let the cat eat what she wants!
Wet food is much better than dry because of the moisture content. Home-cooked diets are ideal, but only if the cat already likes them. Don’t try to switch foods if your cat is sick or has no appetite. The most important thing is for your cat to keep eating. Visit Dr. Lisa Pierson’s website CatInfo.org for detailed articles and instructions on homemade cat food for cats with kidney disease.
Traditional Chinese Medicine (TCM)
Practitioners have found that several TCM herbal formulas may be helpful in slowing and even reversing early chronic kidney disease. Please consult the AHVMA directory to find a certified practitioner near you.
Holistic Supplements
These may support kidney function and reduce inflammation:
- Omega-3 fatty acids are very beneficial in CKD. I recommend Moxxor green-lipped mussel oil for its great bioavailability, mild taste, tiny capsule size, and excellent benefits.
- Antioxidants help manage inflammation in the body and may be able to slow progression of CKD. See Antioxidants for more info.
- Biosuperfood. A nutrient-rich blue-green algae that helps with detoxification and provides important trace nutrients.
- Probiotics like Azodyl™ and Felix’s Flora (Adored Beast) may help reduce blood toxins in CKD cats.
- Renafood (Standard Process). For kidney detox and nutritional support—crush into food; 1–2 tablets daily.
- Feline Renal Support (Standard Process): A formula for cats, though some find Renafood works better.
Note: Standard Process sells only through qualified practitioners. Unauthorized sources may be selling counterfeits or expired products. If you don’t have a distributor nearby, I am happy to work with you. Visit ____ , fill out and email the form. I travel a lot but I will get back to you within a few days.
Fluids: The Most Effective Treatment
Cats with CKD cannot physically drink enough water to stay hydrated. Subcutaneous fluids (given under the skin) are beneficial. They are virtually mandatory to keep your cat eating and feeling well. For most cats, they’re easy to administer at home—your veterinarian or vet tech can show you how.
In more serious cases, your cat may need IV fluids at a clinic for a few days, followed by home care. [Click here for instructions.]
Other Holistic Therapies
- Homeopathy
- Traditional Chinese Medicine
- Acupuncture
- Flower essences (like Jackson Galaxy’s Senior Support)
- Western herbs
Further Reading & Support
- Tanya’s Comprehensive Guide to Feline Chronic Kidney Disease. This is fantastic resource full of in-depth information and support: felinecrf.org
- Pet Loss Support: Losing a cat to CKD can be heartbreaking. You’ll find emotional support resources on Tanya’s site and elsewhere.