Tanya's Comprehensive Guide to Feline Chronic Kidney Disease

Potassium imbalances are common in CKD cats.
Potassium helps muscles, including the heart, to function, so it is important to keep it within a healthy range.
Low potassium levels (hypokalaemia) occur in around 30% of CKD cats. The most usual treatment is an oral potassium supplement.
High potassium levels (hyperkalaemia) occur in around 13% of CKD cats, who usually have more advanced CKD. These are harder to manage, but there are a few possible treatments.

Why Potassium Imbalances Are Important Back to Page Index

Potassium is an electrolyte (body salt) which acts in concert with sodium. It is used at cellular level, and two of its most important functions are to help muscles function smoothly, and, since the heart is a muscle, regulation of the heart rhythm.

Imbalances are quite common in CKD cats. In the earlier stages of CKD, potassium levels are usually too low because potassium is lost in the increased urination and vomiting commonly seen in CKD cats. Low potassium levels are known as hypokalaemia. One study, Feline renal failure: questions, answers, questions (1992) Lulich JP, Osborne CA, O’Brien TD and Polzin DJ Compendium on Continuing Education for the Practising Veterinarian 14 pp127-153, estimated that approximately 30% of CKD cats have low potassium levels.

However, in cats whose CKD is relatively advanced (in IRIS stage 4, with creatinine over 5), the opposite problem may occur and potassium levels may become too high - this is known as hyperkalaemia. Occasionally hyperkalaemia is also seen in cats with less severe CKD. The study mentioned above (Lulich et al., 1992) found that around 13% of CKD cats have hyperkalaemia. Thomas had this problem towards the end, when his creatinine was over 7 for about a month and he did develop extremely high potassium levels during his last few days.

Low potassium levels can damage the kidneys and may make CKD progress more quickly, and may contribute to the development of both metabolic acidosis and hypertension. If your cat has low potassium levels and metabolic acidosis, it is very important to treat both conditions because, as Dr D Polzin states in Chronic Renal Failure (2001) "potassium depletion and metabolic acidosis may promote potentially fatal reductions in plasma taurine concentrations in cats."

High potassium levels may cause heart problems, which in the worst case could result in heart failure.

Therefore it is essential to monitor your cat's potassium levels regularly and to treat any imbalances which may arise.

Symptoms of Low Potassium Levels Back to Page Index

Most CKD cats with potassium imbalances have low potassium levels because potassium is lost from the body in the increased urination and vomiting commonly seen in CKD. These are the most common symptoms of low potassium levels. Rather confusingly, two of them (twitching and lethargy) may also be symptoms of high potassium levels.

Twitching, trembling or shaking

Weakness and muscle wasting

Stilted gait in the front legs

Stiff neck or inability to hold up head

Hoarseness

Increased night time urination
Constipation
Lethargy

Trouble breathing

Appetite loss

Twitching, Trembling or Shaking

Low potassium levels can cause twitching, trembling or shaking. Other possible causes include high potassium levels, high toxin levels, high phosphorus levels, high blood pressure, calcium imbalances (especially head twitching), hyperthyroidism or Vitamin B deficiency. If your cat only twitches while you are giving fluids, it is probably caused by either the type of fluid used or by giving cold (room temperature) fluids.

Pharaoh's Shakes is a video showing a CKD cat twitching.

Weakness, Especially in the Back Legs

Weakness may be seen in the back legs. This is a common symptom of low potassium levels. You may also see a plantigrade posture, where the cat walks on his/her hocks instead of his/her feet, like Ollie to the left. His back half also seemed to sway when he walked. This photo was taken a day after he came to live with us a week before his 16th birthday. He saw the vet that day and since his potassium level was at thevery bottom of the range (3.5), she started him on a potassium supplement - he had his first dose just after this photo was taken. There was improvement within 24 hours, and within 48 hours he was walking normally again.

A plantigrade stance can have other causes. It is most likely to occur in diabetic cats, caused by diabetic neuropathy. The Mayo Clinic has information about peripheral neuropathy, including that caused by diabetes. Long Beach Animal Hospital has a photograph of a cat with diabetic neuropathy doing this (click on Symptoms). Newman Veterinary has a good before and after photo of a diabetic cat with this problem, scroll down a little to Other Common Consequences, then click on Plantigrade Stance (in red font).

Back leg weakness and/or a plantigrade stance may also be caused by high phosphorus levels which interfere with the nerve messages that control the limbs, a condition known as peripheral neuropathy. Occasionally the cause is low magnesium or low calcium levels.

General weakness may be caused by anaemia, or because the cat is simply not eating enough. It is essential that cats eat, because if they do not eat, they are at risk of developing a potentially life-threatening condition called hepatic lipidosis. The Persuading Your Cat to Eat page has tips on persuading your cat to eat.

If your cat no longer jumps, this may be thought to be weakness when in fact it is an unwillingness to jump because of blindness caused by hypertension. An inability to jump or climb may also be caused by arthritis.

Stilted Gait in the Front Legs

This is usually a sign of low potassium levels.

Stiff Neck or Inability to Hold Up Head (Ventroflexion)

The cat may be unable to raise his or her head properly - in most CKD cats, this is a symptom of potassium deficiency. Very occasionally, this may be a sign of thiamine (Vitamin B1) deficiency, which is sometimes seen in cats fed too much fish.

Diagnosis and management of chronic renal failure in cats (2000) Sparkes A, has a photo on page 4 of a cat with this condition.

Long Beach Animal Hospital has a photograph of a cat with this problem - scroll down to find the photograph.

The feline patient: cervical ventroflexion (2007) Mitchell A Crystal discusses this problem and also has a photograph. If necessary, search for "ventroflexion cat" to find the relevant book and page - it should be the first one in the list.

Hoarseness

This can be caused by low potassium levels adversely affecting the vocal chords. Alternatively, this is sometimes a sign of stomach acid. If accompanied by coughing, consider the possibilities of fluid build-up and/or heart problems.

Trouble Breathing

This can be a sign of low potassium levels or metabolic acidosis. Other possible causes include fluid build-up, heart problems or anaemia.

Increased Night-time Urination

One peculiarity which you may see is nocturia, or excessive urination during the night, which may be caused by low potassium levels. If you only give your cat sub-Qs late at night, this might also be the cause.

Constipation

This may be a sign of low potassium levels. It may also be caused by dehydration or high calcium levels.

Lethargy

This may be a sign of low or high potassium levels, anaemia or hypertension. Lethargy may sometimes be a sign of heart problems, especially if it appears after giving fluids.

Loss of Appetite

Low potassium levels may be a factor in a cat having a poor appetite.

Symptoms of High Potassium Levels Back to Page Index

Cats whose CKD is relatively advanced (IRIS stage 4, with creatinine over 5) may develop high potassium levels. These are the usual symptoms. Rather confusingly, two of them (twitching and lethargy) may also be symptoms of low potassium levels.

Twitching, trembling or shaking

Seizures

Lethargy

Seizures

With high potassium levels, heart problems can arise, and short seizures may also occur, especially in end stage renal failure.

Seizures may take a number of different forms. There may be the classic jerking and loss of consciousness, but being "spaced out" or mentally absent or staring into space may also be a type of seizure. Harpsie' s website has more information on what seizures may look like.

Seizures can also be a sign of high blood pressure, high levels of toxins, metabolic acidosis or of calcium imbalances. The use of Reglan (metoclopramide) for stomach problems or Advantage for fleas may lower the seizure threshold. Other possible causes of seizures include epilepsy or a brain tumour, but the causes mentioned above are far more likely in a CKD cat and should therefore be considered first.

Twitching, Trembling or Shaking

Twitching may be related to potassium levels in the body. In early CKD, it is likely to be due to potassium levels being too low,but in cats with higher bloodwork levels, potassium levels may rise and cause twitching as happened to Thomas on his last day.

Other possible causes include high toxin levels, high phosphorus levels, high blood pressure, calcium imbalances (especially head twitching), hyperthyroidism or Vitamin B deficiency. If your cat only twitches while you are giving fluids, it is probably caused by either the type of fluid used or by giving cold (room temperature) fluids.

Pharaoh's Shakes is a video showing a CKD cat twitching.

Lethargy

This may be a sign of high or low potassium levels, anaemia or hypertension. Lethargy may sometimes be a sign of heart problems, especially if it appears after giving fluids.

Measuring Potassium Levels Back to Page Index

A bloodtest will tell your vet if your cat's potassium level is too low or too high. However, sometimes the level may look artificially high or artificially low:

If the sample is haemolysed (the blood cells in the sample have ruptured), the potassium level may look higher than it actually is, though occasionally it will look lower than it actually is.
If the sample has sat around for a while before being tested, the potassium level may look artificially high.
A cat with a very high white blood cell count, perhaps because of infection, may have artificially low potassium levels.
In a cat with metabolic acidosis, the potassium level may appear normal or high in blood tests, but may subsequently fall after the metabolic acidosis is treated.

Conversely, potassium levels may appear to be normal when in fact there is a deficiency. Dr D Polzin states in Chronic kidney disease (2006) "muscle potassium content decreased in normokalemic cats with spontaneous CKD, indicating that a total-body deficit of potassium may develop well before the onset of hypokalemia." This is because, although potassium is used in the body's cells, the regulatory mechanism of the body is actually set to maintain a certain level of potassium in the blood, not the cells. Thus, when potassium levels drop, as they tend to do in early stage CKD, the cat's body will try to maintain levels of potassium in the blood by taking potassium from the cells. This means that at the intra-cellular level where the potassium is really needed, potassium levels are too low, even though the blood levels of potassium may appear to be normal.

There are a number of tests available for humans to test potassium at the intracellular level. One is the Exa Test, which requires a buccal sample (from the cheek inside the mouth). I only know of one person who has had potassium checked at the intracellular level, but unfortunately he cannot remember which company his vet used.

Other Causes of Low Potassium Levels Back to Page Index

Cats with diabetes may have low potassium levels.

Hyperaldosteronism

Very occasionally, low potassium levels may be caused by a condition known as hyperaldosteronism. This may make the CKD progress faster, so it is important to treat it if present. It is more common in cats with hyperthyroidism.

Aldosterone is a hormone which regulates sodium and potassium levels in the blood. In hyperaldosteronism, too much aldosterone is produced (usually because of a benign tumour on the adrenal glands), so the cat will develop low potassium levels and high sodium levels which eventually lead to hypertension (high blood pressure). If your cat has low potassium levels and low magnesium levels, and the potassium does not rise even after treating the low magnesium, ask your vet to rule out hyperaldosteronism, especially if your cat has hypertension.

Treatment is the same as for CKD cats with these problems, i.e. potassium supplements and medication to control the high blood pressure, though surgery to remove the affected adrenal gland is also an option in some cases, and may completely resolve the problem for some cats.

Less common feline endocrinopathies (2004) is a presentation by BR Jones to the World Small Animal Association World Congress 2004. Scroll to the last section for information on hyperaldosteronism.

Primary hyperaldosteronism in the cat: a series of 13 cases (2005) Ash RA, Harvey AM & Tasker S Journal of Feline Medicine & Surgery 7(3) pp173-82 states that "it is recommended that primary hyperaldosteronism should be considered as a differential diagnosis in middle-aged and older cats with hypokalaemic polymyopathy and/or systemic hypertension and should no longer be considered a rare condition."

Primary hyperaldosteronism in cats - an underdiagnosed disorder (2010) Kooistra HS Presentation to the World Small Animal Veterinary Association World Congress explains more about diagnosis and treatment.

Goal for Potassium Level in Bloodwork Back to Page Index

In 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine December 2007, Dr Polzin states "Intervention to manage serum potassium concentrations is indicated in dogs and cats when the concentrations fall outside the target range of 3.5 to 5.5 mEq/L, regardless of the chronic kidney disease stage."

Thus Dr Polzin recommends starting treatment if potassium is outside the laboratory range. However, because of the problems in measuring levels of potassium in the cells accurately, and since hypokalaemia may damage the kidneys and make the CKD progress more quickly, and may contribute to the development of both metabolic acidosis and hypertension, it may be appropriate to supplement potassium in CKD cats when it falls below the middle of the normal range. For most laboratories, this would mean supplementation for cats whose potassium level is below 4.0 mmol/L/l (US: 4.0 mg/dl). The reason for this is that if it is impossible to raise the levels in the blood to the middle of normal, it must be because the cells are depleted to such an extent that they cannot release any more potassium into the blood.

My Ollie had a potassium level of 3.5 at diagnosis, which was technically within range. However, he could barely walk (see the photo above). My vet started him on a potassium supplement and within two days he could walk normally again.

In Chronic renal failure in the cat (2006) Sparkes A, Presentation to the World Small Animal Veterinary Association World Congress Dr Sparkes states "Potassium concentrations should be monitored regularly in cats with CKD and if they fall below 4 mmol/l, supplementation with potassium salts is recommended."

In 11 guidelines for conservatively treating chronic kidney disease (2007) Polzin D, Veterinary Medicine December 2007, Dr Polzin himself states on page 3 "The goal of therapy for hypokalemia is to bring the serum potassium concentration above 4 mEq/L."

Treating Low Potassium Levels (Hypokalaemia) Back to Page Index

Diet and fluids
Potassium supplements

Diet and Fluids

Prescription renal foods contain additional potassium, as do some types of sub-Q fluids, and for mild hypokalaemia either or both of these treatments may be enough to resolve the problem. If additional treatment is necessary, the usual treatment for low potassium levels is an oral potassium supplement. Occasionally potassium is added to the sub-Q fluid bag instead, but this can sting.

Pet Place discusses hypokalaemia in cats.

Cornell University College of Veterinary Medicine has some information about low potassium levels.

Penn State University College of Medicine has some information on low potassium levels in humans.

Potassium Supplements Back to Page Index

Types of supplement
Dosage
Sources

Types of Supplement

There are three main types of potassium supplement:

potassium gluconate - this is what most people use.
potassium citrate - this can be helpful for cats who also have metabolic acidosis.
potassium chloride - the oral form is not recommended, but the injectible form is used when potassium is added to sub-Qs.

Unfortunately, oral potassium supplements can make some cats vomit more - after all, potassium is a type of salt, and salt would give anyone a stomach upset if taken neat. Supplements may also cause diarrhoea in some cats. The solution is to try to spread them out more and mix them in with foods. Most people find the powder form or crushed pills easiest to use, because the daily dose can be spread over several meals. If the problem persists, ask your vet about changing the brand and/or formula you are using in case that helps.

ACE inhibitors such as benazepril (Fortekor) may make potassium levels rise; so if your vet has prescribed Fortekor, as many British vets do, your vet should monitor potassium levels carefully and adjust the dose as appropriate.

In terms of monitoring, Dr D Polzin recommends in Renal disease (2006) that cats with severe symptoms (such as multiple muscle weakness) should be monitored every 24-48 hours when first beginning to supplement, and that all cats should be checked every 7-14 days until the appropriate maintenance dose is established.

Never administer potassium supplements without your vet's approval - an overdose of potassium can cause heart failure. It is not recommended to give potassium to a cat with a high creatinine level (above 500, USA above 6) without the cat being monitored closely by a heart specialist. Cats with creatinine at this level often have high levels of potassium and do not require a potassium supplement anyway. Potassium should also never be given to a cat who cannot urinate.

Combined Supplements

If you are in the UK, you may be offered a product called Kaminox. This is a combination of B vitamins, iron and potassium gluconate. Alfamedic provides a list of the ingredients.

In the USA there are two products available containing potassium and B vitamins, Renal K+ made by Vetoquinol, and Amino B & K from Emerson Ecologics.

Potassium Gluconate

Dosage

In Renal disease (2006) Dr D Polzin recommends "Depending on the size of the cat and severity of hypokalemia, potassium gluconate is given initially at a dose of 2 to 6 mEq per cat per day." He further recommends that potassium levels should be monitored every 24-48 hours when first beginning to supplement for cats with severe symptoms, and thereafter every 7-14 days. Do not supplement potassium without your vet's knowledge and approval, because not all CKD cats have low potassium levels, and giving potassium to a cat who does not need it can be very dangerous. Potassium should never be given to a cat who cannot urinate.

It can be rather tricky calculating potassium doses because there is a difference between potassium and elemental potassium, which is what dosages are based on.

Plumb's Veterinary Drug Handbook (6th Edition) states that 1 gram (1000mg) of potassium gluconate contains 4.3 mEq of potassium, which is approximately 168 mg of elemental potassium.

Tumil-K contains 468mg of potassium gluconate, which means it contains 78mg of elemental potassium. The atomic weight of potassium is 39 which means this is 2 mEq of elemental potassium. The manufacturer recommends 2 mEq per 10 lbs (4.5kg) body weight twice per day. This is contained in one caplet, half a teaspoonful of gel or a quarter of a level teaspoon (0.65g) of the powder. I used this dosage for Ollie on my vet's advice and Ollie's symptoms improved within two days, but be guided by your vet as to an appropriate dose for your cat.

Potassium supplements for humans are widely available in health food shops without prescription, often very cheaply, for US$4 or so for 100 pills, so many people use these with their vet's approval. Most human potassium gluconate tablets contain more elemental potassium than Tumil-K because Tumil-K is flavoured (the flavourings take up room). However, the amount of elemental potassium in an over the counter supplement in the USA cannot exceed 99mg, so most potassium gluconate tablets for humans contain 99mg of elemental potassium, which is 590mg of potassium gluconate and 2.53 mEq. This means that 0.79% of this strength of tablet is the equivalent of Tumil-K, so to obtain 2 mEq you would give three quarters of a tablet. The NOW brand of powdered potassium gluconate is stronger than this: it contains 650 mg of potassium gluconate in 1/4 tsp, which is 135mg of elemental potassium or 3.45meq. In other words, an eighth of a teaspoon of the NOW brand powder is equal to a bit less than the usual Tumil-K dose of half a teaspoon.

Tumil-K is a veterinary formula stocked by many vets. It is rather expensive, but is a good choice because it does not contain phosphorus. It comes in powder, caplet or gel form. Drugs has some information about it.

Potassa-Chew is a chewable form of potassium gluconate. The manufacturers claim over 60% of cats will eat this willingly as a type of treat.

Renakare is a generic version of potassium gluconate which comes in tablet, powder or gel form.

Drugs has some information about potassium gluconate.

Potassium Citrate

This is a good choice for cats who also have metabolic acidosis. In fact, Dr D Polzin says in Renal disease (2006) that other treatments for metabolic acidosis in cats who also have low potassium levels may only be of limited use. He recommends Polycitra-K in syrup form. He states that a common starting dose is 40 to 60 mg per kg of cat per day (18 to 27 mg per pound of cat) divided into 2 or 3 doses.

Potassium citrate must be given at least two hours apart from any phosphorus binders containing aluminium, because citrate may increase the absorption of aluminium. Potassium citrate is not recommended for use in cats who are prone to forming struvite crystals in the urine. However, this means it may be suitable for cats with calcium oxalate stones.

Urocit-K. is one brand.

Drugs has some information about potassium citrate.

Potassium Chloride

Some vets recommend potassium chloride because it is cheaper. Few people use potassium chloride in the oral form because it may contribute to metabolic acidosis, but if you want to give potassium by adding it to your cat's sub-Q fluids, this is the type you would use.

Injectible Potassium Chloride

This is available in a 2 mEq/ml strength, in either 10ml or 20 ml vials. If your vet adds the 10ml strength vial to your bag of 1000ml sub-Q fluid, the bag now contains 20 mEq of potassium. If you are giving 100ml a day of fluids, you are giving 2 mEq of potassium each day, or the equivalent of one Tumil-K caplet a day. If you give potassium in this way, be aware that it can sting.

Slow-K is one brand.

Drugs has some information about potassium chloride.

Supplies

Thriving Pets sells a variety of potassium supplements. If you enter the word "tanya" (without the ") in the promotional code box, you will receive a 10% discount on orders over US$55. Shipping is free for orders over US$55 after the discount.

Potassium Gluconate

Many people simply buy over the counter human brands of potassium gluconate at their local health food store without prescription for US$4 or so for 100 pills which they can then crush and add to their cat's food. Be very careful about the dosage if you do this, because human potassium supplements are stronger than most veterinary supplements.

Thriving Pets sells a 200g jar for US$19.95. If you enter the word "tanya" (without the ") in the promotional code box, you will receive a 10% discount on orders over US$55. Shipping is free for orders over US$55 after the discount.

KV Vet Supply sells 100 tablets for US$21.95.

Lucky Vitamin sells the NOW brand in powder form at US$8.48 for 1 lb with flat rate shipping.

Potassa-Chew is a chewable form of potassium gluconate. The manufacturers claim over 60% of cats will eat this willingly as a type of treat. It is available from California Veterinary Supply.

Renal K+ (with Added Vitamin B)

Renal K+ Fact Sheet gives more information about the product, but does not specify the precise amounts of B vitamins contained in it.

Thriving Pets sells 100g in powder form for US$12.95. If you enter the word "tanya" (without the ") in the promotional code box, you will receive a 10% discount on orders over US$55. Shipping is free for orders over US$55 after the discount.

Amazon sells 100g in powder form for US$15.20 with free shipping.

Vetscriptions sells 100g of Tumil-K powder for £32.99.

Treating High Potassium Levels (Hyperkalaemia) Back to Page Index

It is important to understand that not all CKD cats need potassium supplements. Some cats never have low potassium levels, particularly if the CKD is relatively advanced (IRIS stage 4, creatinine over 5). Thomas's creatinine was not that high, yet he never needed potassium. Feline renal failure: questions, answers, questions (1992) Lulich JP, Osborne CA, O’Brien TD and Polzin DJ Compendium on Continuing Education for the Practising Veterinarian 14 pp127-153) found that around 13% of CKD cats have high potassium levels. Therefore you should not supplement potassium without a bloodtest and your vet's approval.

If your cat has high potassium levels (over 6), this is potentially very dangerous, and may cause seizures and even a heart attack. But don't panic: quite often bloodwork may indicate high potassium levels when in fact it is an error caused by a haemolysed blood sample or by leaving the blood for a while before testing it. Your vet will probably re-run the test to be sure that you really are dealing with high potassium levels.

If, however, your cat does indeed have high potassium levels (which is relatively common in cats with creatinine over 5), it is important to try to reduce them. Unfortunately it is not always easy to control hyperkalaemia, particularly if your cat is no longer urinating much or at all. The first thing to do, of course, is to stop all potassium supplements. Increased fluid therapy may help but you would probably need to use saline fluid rather than lactated ringers solution, which contains potassium. Using benazepril (Fortekor) may increase potassium levels, so you may need to reduce or stop this treatment, although you should only do this with veterinary approval and you may need to reduce the drug gradually rather than suddenly.

For really high potassium levels, sometimes insulin may be administered in conjunction with dextrose or sodium bicarbonate, which work together to move potassium intra-cellularly. If your cat has oliguria (reduced urination), diuretics such as Lasix (furosemide) may be suggested by your vet in an attempt to get urine flowing again. Pet Place reports that albuterol, a bronchodilator commonly used to help open the airways during asthma attacks, has also been used in treating hyperkalaemia associated with CKD.

In extreme cases, your vet may choose to use a potassium exchange resin: I heard from one person who successfully used a human drug called sodium polystyrene sulfonate (potassium kayexolate) which has apparently been used to a limited extent in dogs but I do not know of anybody else who has used this for a cat. Potassium levels need to be monitored daily when using this treatment.

Doyle Medical has information on the use of these drugs in human emergency medicine, scroll down to Treatment of Hyperkalaemia Using Insulin.

PetMD discusses high potassium levels.

Cornell University College of Veterinary Medicine has some information on hyperkalaemia.

Medline discusses high potassium in humans, but the basic principles are similar for cats.

E Medicine is a human site with information on hyperkalaemia.

Endocrine Emergencies is a presentation by Dr MS Wallace to the Atlantic Coast Veterinary Conference 2001.

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This page last updated: 08 November 2011

Links on this page last checked: 08 November 2011