How Bad Are My Cat's Results: The Stages of CKD Using the International Renal Interest Society (IRIS) Staging System

If Your Cat Seems to Have Lost a Massive Percentage of Function 

Chronic Renal Failure Versus Chronic Kidney Disease

End Stage Renal Disease (ESRD)

If Your Vet Has Recommended Euthanasia

What Does All This Mean in Practical Terms? 



Tanya's CKD Support Group Today



Site Overview

What You Need to Know First

Alphabetical Index


Research Participation Opportunities

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What Happens in CKD?

Causes of CKD

How Bad is It?

Is There Any Hope?

Acute Kidney Injury



Nausea, Vomiting, Appetite Loss and Excess Stomach Acid

Maintaining Hydration

The Importance of Phosphorus Control

All About Hypertension

All About Anaemia

All About Constipation

Potassium Imbalances

Metabolic Acidosis

Kidney Stones



Coping with CKD

Tanya's Support Group

Success Stories



Alphabetical List of Symptoms and Treatments

Fluid and Urinary  Imbalances (Dehydration, Overhydration and Urinary Issues)

Waste Product Regulation Imbalances (Vomiting, Appetite Loss, Excess Stomach Acid, Gastro-intestinal Problems, Mouth Ulcers Etc.)

Phosphorus and Calcium Imbalances

Miscellaneous Symptoms (Pain, Hiding Etc.)



Blood Chemistry: Kidney Function, Potassium, Other Tests (ALT, Amylase, (Cholesterol, Etc.)

Calcium, Phosphorus, Parathyroid Hormone (PTH) and Secondary Hyperparathyroidism

Complete Blood Count (CBC): Red and White Blood Cells: Anaemia and Infection

Urinalysis (Urine Tests)

Other Tests: Ultrasound, Biopsy, X-rays etc.

Renomegaly (Enlarged Kidneys)

Which Tests to Have and Frequency of Testing

Factors that Affect Test Results

Normal Ranges

International and US Measuring Systems



Which Treatments are Essential

Fluid and Urinary Issues (Fluid Retention, Infections, Incontinence, Proteinuria)

Waste Product Regulation (Mouth Ulcers, GI Bleeding, Antioxidants, Adsorbents, Azodyl, Astro's CRF Oil)

Phosphorus, Calcium and Secondary Hyperparathyroidism (Calcitriol)

Miscellaneous Treatments: Stem Cell Transplants, ACE Inhibitors - Fortekor, Steroids, Kidney Transplants)

Antibiotics and Painkillers

Holistic Treatments (Including Slippery Elm Bark)

ESAs (Aranesp, Epogen etc.) for Severe Anaemia

General Health Issues in a CKD Cat: Fleas, Arthritis, Dementia, Vaccinations

Tips on Medicating Your Cat

Obtaining Supplies Cheaply in the UK, USA and Canada

Working with Your Vet and Recordkeeping



Nutritional Requirements of CKD Cats

The B Vitamins (Including Methylcobalamin)

What to Feed (and What to Avoid)

Persuading Your Cat to Eat

Food Data Tables

USA Canned Food Data

USA Dry Food Data

USA Cat Food Manufacturers

UK Canned Food Data

UK Dry Food Data

UK Cat Food Manufacturers

2007 Food Recall USA



Intravenous Fluids

Subcutaneous Fluids

Tips on Giving Subcutaneous Fluids

How to Give Subcutaneous Fluids with a Giving Set

How to Give Subcutaneous Fluids with a Syringe

Subcutaneous Fluids - Winning Your Vet's Support




Heart Problems



Polycystic Kidney Disease (PKD)


Dental Problems









The Final Hours

Other People's Losses

Coping with Your Loss



Early Detection



Canine Kidney Disease

Other Illnesses (Cancer, Liver) and Behavioural Problems

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Home > What is CKD? > How Bad Is It?



  • This is usually one of the first questions people ask themselves after diagnosis. 

  • This page attempts to help you understand a bit more about what the test results mean, and why they do not tell the whole story.

  • It also explains why it is not as bad as it sounds when your vet says your cat has lost a certain percentage of his/her kidney function.

How Bad Are My Cat's Results?


There are a number of ways in which the vet can determine how advanced your cat's case is. Most vets will start with bloodwork, and many will also analyse your cat's urine (urinalysis).


Many vets now take the test results and categorise them according to the system proposed by the International Renal Interest Society. This divides CKD into four stages based on blood and urine test results; so if your vet tells you, for example, that your cat is in Stage 2, s/he is probably referring to the IRIS staging system. There is more information on this below.


Remember, your cat's test results are only part of the story. There are other factors at play, including how your cat is acting, how proactive your vet is, whether there is an infection etc. For this reason, we have a mantra on Tanya's CKD Support Group: treat the cat, not the numbers.


Bloodwork tells vets quite a lot about how a cat's kidneys are functioning. BUN (urea) and creatinine are the two main measures of kidney function in bloodwork. Here is the IRIS staging system, with my estimate of the likely percentage of function lost:


Stage of Disease

Blood Values:

US Measurements (mg/dl)

Blood Values:

International Measurements (µmol/L)

Approx. Level of Kidney Function Lost

Stage 1

Creatinine below 1.6

Creatinine below 140

 0 - 65%

Stage 2

Creatinine between

1.6 and 2.8

Creatinine between

140 and 249


66 - 75%

Stage 3

Creatinine between

2.9 and 5.0

Creatinine between

250 and 439


76 - 90%

Stage 4

Creatinine over 5.0

Creatinine over 440

Over 90%

*It is normal not to be able to detect CKD until at least 66% of function has been lost, because before that there are usually no symptoms, see below. Therefore for cats in Stage 1, bloodwork values are usually within the normal range, and kidney problems would only be suspected if an anatomical or functional abnormality had been detected.


In all cases, two readings in a stable cat (who is not dehydrated - this can make the numbers look a lot higher than they really are), ideally after fasting (though that is not always the best choice for a CKD cat), are required before making a firm diagnosis of CKD. In practice, most vets will make the diagnosis based on bloodwork taken once during your initial visit.


Urine Specific Gravity (USG)

Because of their desert heritage, healthy cats have concentrated urine. The normal range is 1.008 to 1.060 but a cat with a more dilute USG, below 1.040, is generally considered to have a problem of some kind. A CKD cat will probably have a USG between 1.008 and 1.012. 


Other possible causes of dilute urine include liver disease, diabetes, hyperthyroidism or use of corticosteroids. Cats with pyelonephritis (kidney infection) may have low USG.


Once a cat is receiving regular fluid therapy, this test can be rather unreliable; but it may be helpful when blood tests first indicate a possible problem, particularly if your cat appears to be in early stage.


There is more information about USG on the Urinalysis page.


The International Renal Interest Society has information on the significance of USG in cats.



The International Renal Interest Society (pages 3 and 4 for cats) also mentions the importance of proteinuria when deciding how advanced a cat's CKD is.


Healthy cats only have tiny amounts of protein in their urine because their kidneys do not allow the protein to leak through. In CKD cats, this mechanism can be faulty and excess levels of protein in the urine, known as proteinuria but sometimes referred to as microalbuminuria, may occur.


The usual way to determine if a cat has proteinuria is via the urine protein:creatinine ratio (UPC):


Urine Protein: Creatinine Ratio

Proteinuria Status

Below 0.2

Non Proteinuric (NP)

Between 0.2 and 0.4

Borderline Proteinuric (BP)

Over 0.4

Proteinuric (P)


There is a correlation between the severity of the proteinuria and the prognosis. However, don't panic if your cat's level is over 0.4 because the UPC ratio is not always accurate - for example, blood in the urine, infection or inflammation may give a false positive result. Hypertension may worsen proteinuria, so getting blood pressure under control may lead to an improvement in the UPC ratio. Even if your cat's UPC ratio is indeed high, it may gradually reduce with treatment.


Relation of survival time and urinary protein excretion on cats with renal failure and/or hypertension (2004) Syme HM, found that cats with a urine protein:creatinine ratio below 0.5 survived almost three times as long as cats with a urine protein:creatinine ratio of over 0.5.

Survival of cats with naturally occurring chronic renal failure is related to severity of proteinuria (2006) Syme HM, Markwell PJ, Pfeiffer D & Elliott J Journal of Veterinary Internal Medicine 20 pp528–535 confirmed the results of the earlier study above.

Idexx Laboratories is now offering a new test in a number of different countries which can calculate the protein:creatinine ratio.

How to integrate UPC ratios into your practice and uncover early renal disease is a video presentation about the new Idexx test (this lasts an hour).


Percentage of Function Lost                                                                             Back to Page Index


You may well panic if your vet tells you that your cat has lost two thirds or more of his/her kidney function. I regularly hear from people who say things like "my vet told me my cat has lost 75% of kidney function and it's looking really bad".


Take a deep breath. It is probably not as awful as you fear because it is actually normal for CKD not to be diagnosed until a cat has lost at least 66% of kidney function. The What Happens in CKD? page has more information on why this is the case.


What you need to focus on is the fact that cats with CKD can often manage quite well on limited kidney function - for some cats, things only become critical when they have lost as much as 90% of function, and there are  some cats who cope astonishingly well with even less function. So the goal is, not to worry about the function that has already been lost, but to try to help your cat manage with whatever function remains for as long as possible.


Chronic Kidney Disease versus Chronic Kidney Failure                            Back to Page Index


You may also be frightened because your vet says your cat's kidneys have failed. Fortunately, this may not be as bad as it sounds.


There are a number of different expressions used to describe chronic kidney disease. It used to be widely known as chronic renal failure (CRF), and for many years this website was known as Tanya's Comprehensive Guide to Feline Chronic Renal Failure.


I decided to changed the name in 2011 and use the expression Chronic Kidney Disease (CKD) instead. This was for two reasons. Firstly, it is the term most commonly used in the academic literature. Secondly, I think it more accurately reflects the nature of the disease, and focuses on the important word, "chronic" rather than on that awful word, "failure", which tends to scare people, making them feel the end is nigh.


Chronic means that CKD is an ongoing disease. This is good news, because it means that in many cases it can be managed. For this reason, some vets prefer to use the word "insufficiency" for early stage cases instead.


Whatever expression your vet uses, try to focus on the chronic aspect of CKD.


End Stage Renal Disease (ESRD)                                                                     Back to Page Index


This expression literally means that the cat's kidneys are at the point of failure and there is no longer anything that can be done. Some vets use it in this sense, referring to a cat who is rapidly becoming unable to deal with the CKD, ceasing to respond to treatments and likely to die very soon. However, other vets use it to mean any cat with numbers in the range of Stage 2 or 3 (see above), when in fact many cats in these stages can live for a long time.


Try to clarify what your vet means by ESRD, and if he/she merely means that your cat has high numbers, consider treating the cat; the numbers may come down with treatment, and even if they don't, your cat might be able to handle high numbers as Thomas did. Even if your vet thinks death is imminent, it may be worth treating your cat regardless to see how he or she responds; cats are real fighters and can often pull through.


Obviously though, you don't want your cat to be in pain when it is a hopeless situation. It is not always easy to tell when a CKD cat has come to the end of the road - The Final Hours contains details of the symptoms you are likely to see towards the end, and discusses making the painful decision to let go.


If Your Vet Has Recommended Euthanasia


When vets tell people there is no hope for their cat, it is usually based on test results as outlined above, particularly blood tests which show high kidney values. However, I have heard of vets who tell people their cat should be put to sleep without doing any tests at all, based purely on the cat acting sick. I don't think this is appropriate. Your vet may be right, there may be no hope for your cat, but if you're thinking of making the irrevocable decision to put your cat to sleep, you need proper, accurate information on which to base your decision.


Even if you do have some blood test results, the numbers only tell part of the story. In Renal disease (2006), Dr D Polzin states "Severity of renal dysfunction as determined by serum creatinine concentration or measurement of GFR provides a less accurate means of assessing short-term prognosis than does the clinical condition of the patient. The relationship between magnitude of renal dysfunction and clinical signs of uremia is often unpredictable. Therefore, short-term prognosis should not be established on the basis of a single measurement of the severity of renal function. In addition, a single determination of renal function is unreliable as an index of the potential for improvement in renal function." In The laboratory diagnosis of feline kidney disease (2008) Heine R Veterinary Focus 18(2) pp16-22, Dr Heine states "cats can sometimes, especially in cases of acute kidney injury secondary to obstructive FLUTD, develop creatinine values of 1600-1800 μmol/L (20.98-23.6 mg/dL) and yet recover."


I don't know why some vets don't try to fight CKD. Perhaps they think it's not worth trying because CKD is incurable. Yes, CKD is incurable, but it can often be managed so your cat feels better. As one member of Tanya's CKD Support Group said, "vets are about the cure, we are about the care."


So try not to worry too much about which stage your cat is in, especially since numbers can be artificially inflated at diagnosis. The stages are supposed to help the vet roughly work out which treatments are likely to be needed, not to encourage them to write off cats in the higher categories. Yes, your cat's chances may be worse if your cat is - and remains - a high numbers cat; but some cats do well despite high numbers, so try treating the cat, not the numbers and see what happens.


Therefore, if your vet has told you there is no hope for your cat, and has recommended euthanasia, I urge you to:

  1. read this page, and also the Is There Any Hope? page to explore the various scenarios you may be facing;

  2. check out the Index of Symptoms and Treatments page to see which symptoms your cat has; and

  3. ask your vet about trying some of the Treatments that are appropriate for any of the symptoms you are seeing and any imbalances indicated by your cat's test results;

before making the irrevocable decision to put your cat to sleep. 

What Does All This Mean in Practical Terms?                                               Back to Page Index


You probably now know into which stage your cat falls, but that doesn't really tell you much about what you are facing on a practical level.


If your cat appears to be in Stage 4, don't despair. You may not be seeing the true situation. Bloodwork can look high for the following reasons:

  • the cat is severely dehydrated

  • the cat has an untreated urinary tract infection or a kidney infection

  • the cat has untreated hypertension (high blood pressure)

  • the cat has kidney stones

The most important thing for cats in all stages is to get food into them! See the Diet and Nutrition chapter for tips and hints.


In addition, you should monitor for:

so you can nip these problems in the bud if they are present.


In virtually all cases it is worth trying treatments for at least two weeks. The International Renal Interest Society has some suggestions on what to watch for and be prepared to treat at each stage, including what to do if proteinuria or hypertension are present.


Whatever stage your cat is at, most people find the treatments only take about 20 minutes out of their day, including the time needed to give sub-cutaneous fluids.

Here are some tips on what you may be facing:

Cat in IRIS Stage 1, Stage 2 or the Lower End of Stage 3

  • If your cat seems to fall into IRIS Stage 1, 2 or the lower end of Stage 3, it is early stage and with proper care and a little luck on your side, your cat could live for years.

  • Most cats in these Stages (creatinine below 3.5-4.0 mg/dl US or 300-350 µmol/L international) will not need subcutaneous fluids and can easily be managed with just a few treatments tailored to the individual cat's needs, e.g. treatment for stomach acid to prevent vomiting, constipation remedies and/or control of elevated phosphorus levels.

  • In all cases, it is essential that your cat eats!

Cat in Stage 4 or the Upper End of Stage 3

  • If your cat seems to fall into Stage 4 or the top end of Stage 3, don't despair. You may not be seeing the true situation. Bloodwork can appear high for the following reasons:


    • the cat is severely dehydrated
    • the cat has an untreated urinary tract infection or a kidney infection
    • the cat has untreated hypertension (high blood pressure)
    • the cat has kidney stones

    In such cases, the numbers you are seeing won't be an accurate representation of true kidney function. You need to treat your cat, particularly any dehydration, before you can know the true status of the kidneys.

  • Even if your cat proves to be at the top of Stage 3 or in Stage 4 following stabilisation, don't give up hope: some cats do seem to manage very well on very little kidney function, and it is possible that your cat might be one such cat. You will probably need to be more proactive and your cat will usually need more treatments than cats with lower bloodwork values, but it is certainly worth trying to help.

  • These cats will usually need the same treatments as cats in lower stages for whatever problems may be present, e.g. for stomach acid, high phosphorus levels, constipation etc. In addition, they will usually need regular fluid therapy in the form of sub-cutaneous fluids in order to avoid dehydration.

  • Cats in IRIS Stage 4 will often have anaemia, and will need treatment for that - untreated severe anaemia can be very dangerous and can kill a CKD cat before the CKD does. Fortunately, many effective treatments for anaemia are available, meaning no CKD cat need die of anaemia. See the Anaemia page for more information.

  • Cats in IRIS Stage 4 may have metabolic acidosis, so ensure your vet checks for that and treats it if it is present.

Please see the Is There Any Hope? page for more information.





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This page last updated: 12 March 2012

Links on this page last checked: 03 December 2011