Hannah Zulueta Canine Nutrition / Kidney Disease
Potassium
The number that decides whether the heart beats
Too much potassium can stop a dog’s heart. Too little takes her strength away slowly, over months. Neither one shows on the outside until late, so the only way to know is a blood test.
The one thing
A dog can sit at 6.2 and look like nothing is wrong
Seventeen pounds, asleep on the couch, looking exactly the way she looked the week before. No cough, no limp, no vomiting, nothing you could photograph and send to the vet. There is a line on a lab report, and if it keeps climbing, the first outward sign can be the last one.
This is not a mineral you manage by watching your dog. It is a mineral you manage by reading her bloodwork, and by knowing which direction hers is drifting.
Start here
Almost none of it is in the blood
Roughly ninety-eight percent of a dog’s potassium lives inside the cells. The blood carries the small remainder, and that remainder is what a serum chemistry panel measures.
So the number on the report is not telling you how much potassium your dog has. It is telling you how much has leaked out of her cells into her blood.
Here is why that leak is dangerous. Every cell keeps potassium inside itself and pushes sodium out. That difference turns the cell into a tiny battery, and the charge on that battery is what fires a nerve and squeezes a muscle. Every heartbeat your dog has ever taken ran on it.
The charge only works if there is far more potassium inside the cell than outside. Let potassium build up in the blood and the gap closes, and the battery goes flat. Let it fall too low and the gap stretches too wide, and the signal turns weak and unreliable. Either way the muscles stop firing properly, and the heart is the one muscle that cannot afford that.
Potassium charges the battery in every cell. Change how much is in the blood, and you change how every nerve and every muscle in your dog fires, all at once.
Which dog is yours
The same diagnosis, two opposite problems
Choose the picture that matches your dog’s last panel.
Above about 5.5 mEq/L. Hyperkalemia.
This is a heart problem, even though it usually starts in the kidney. It is almost always a failure to get rid of potassium, not too much coming in. Food only starts to count once the kidney has stopped clearing it.
Standard renal diets add potassium. For this dog, the food she was prescribed may be pushing up the exact number that is already too high.
Below about 3.5 mEq/L. Hypokalemia.
This is the more common electrolyte problem in chronic kidney disease, and the one that gets missed, because it comes on slowly. Weak back end, stiff gait, poor appetite, sluggish gut, more drinking and more urinating.
For this dog, a well-formulated renal diet is working with her. The added potassium in the bag is a feature, not a flaw.
Roughly 3.5 to 5.5 mEq/L. Normal for most labs.
A healthy dog with working kidneys and a working adrenal gland excretes potassium generously, with a wide margin. You could not feed a normal dog into a dangerous number using food.
Worth knowing where in the range she sits, though. In a dog whose kidneys are failing, a potassium sitting at the top of the range is a different situation from one sitting in the middle, even though both get called normal.
Too high
The heart stops being able to reset
When potassium builds up in the blood, the battery runs down. At first the heart cell sits closer to firing, which sounds like it should make the heart quicker to respond. It does, briefly. Then the tiny gates that start each beat get stuck open and stop resetting, and the cell can no longer recharge between contractions.
The electrical signal slows down. It normally runs from the top chambers of the heart to the bottom ones in a clean order. Now it smears. On an ECG the changes arrive in this order.
In dogs those ECG changes track the potassium number loosely rather than precisely, so a normal-looking tracing is not reassurance. But the order tells you which way things are heading, and it explains why high potassium is a heart emergency, not just a bad kidney result.
Labs differ. Always read against the reference interval printed on your own report.
The one sign worth memorizing: a slow heart rate. A dog who is sick and has a heart rate in the fifties or sixties is a dog whose potassium needs checking that day. Most sick dogs run fast. A sick dog running slow is a different problem. Weakness in the back end, reluctance to move, a dog who lies down and stays down, and collapse all belong on the same list.
Where high potassium comes from
Kidneys that cannot excrete
Acute kidney injury, and the late stages of chronic kidney disease where urine output falls off. There is also a specific pattern in chronic kidney disease where the kidney stops responding to the aldosterone signal and holds potassium even while other functions look stable.
A blocked or ruptured bladder
A male dog straining unproductively is an emergency for exactly this reason. So is a bladder rupture after trauma, where urine sits in the abdomen and the potassium is reabsorbed straight back into circulation.
Addison’s disease
Without aldosterone the kidney cannot dump potassium or hold sodium. The classic pattern is a high potassium sitting next to a low sodium, which is why sodium should always be read alongside it.
Medications
ACE inhibitors such as benazepril and enalapril, ARBs such as telmisartan, spironolactone, and NSAIDs layered on top of any of them. The same mechanism that protects the kidney and reduces protein loss also reduces potassium excretion. This is a conversation with your vet about balance, not a reason to stop a drug.
Acidosis and cell breakdown
Metabolic acidosis, crush injury, or any event causing massive cell breakdown pushes potassium out of the cells and into the blood. The total body amount has not changed. Its location has.
Diet does not cause high potassium in a dog whose kidneys and adrenal glands work. Food only starts to count once the kidney has stopped clearing it.
Before you panic, check the tube
A hemolyzed blood sample releases potassium out of ruptured red cells and falsely raises the result. So does a sample that sat too long before being spun. Akitas, Shiba Inus, and several other Japanese breeds carry unusually high potassium inside their red cells, which makes them especially prone to a falsely high reading. Very high platelet or white cell counts can do it too. A single surprising potassium in a dog who looks and acts fine is worth repeating on a clean sample before anyone changes anything.
Too low
Too little is slower, and easier to miss
Below 3.5 mEq/L is hypokalemia. Below 2.5 is severe.
Nothing dramatic happens at 3.2. That is exactly the problem. Low potassium wears a dog down slowly, and by the time an owner brings it up, it has usually been going on for weeks.
- Generalized muscle weakness. The dog walks like the ground is further away than it used to be.
- Ventroflexion of the neck. Head carried low, chin toward the chest. Textbook in cats, less common in dogs, unmistakable when you see it.
- A stiff, short, shuffling gait. Exercise intolerance that gets blamed on age.
- Constipation and sluggish gut motility, because smooth muscle needs potassium the same way skeletal muscle does. Paralytic ileus in the worst cases, which owners describe as bloating.
- Increased drinking and increased urinating, because low potassium damages the kidney’s ability to concentrate urine.
- In severe cases, muscle breakdown, weakness of the breathing muscles, and arrhythmias. The arrhythmia risk climbs sharply if the dog is also on digoxin.
Two loops that make it worse
Low potassium injures the kidney tubules. The injured kidney wastes more potassium. That circle is well documented, and it is why a mild number left alone for months is not benign.
The second loop runs through appetite. A dog with kidney disease feels nauseated and eats less. Less food means less potassium coming in, while the renal losses continue at the same rate. The number drops, the dog gets weaker, and the weaker dog eats less again. In chronic kidney disease, appetite often moves potassium more than any ingredient choice does.
Where low potassium comes from
- Chronic kidney disease, through tubular wasting
- Vomiting and diarrhea
- Furosemide, torsemide, and thiazide diuretics. Any dog on long-term furosemide for heart disease is a dog whose potassium should be tracked
- IV or subcutaneous fluids given without potassium, which dilute what is there while flushing more out
- Insulin therapy, and the treatment phase of diabetic ketoacidosis, which drive potassium back into cells
- Alkalosis, which does the same thing
- The diuresis that follows relief of a urinary obstruction
Adding potassium-rich foods often does not fix a low potassium, and here is why.
A low number is usually a loss problem, not an intake problem. The kidney is leaking potassium faster than the bowl can replace it, and the leak is what needs attention. Magnesium is the most commonly missed reason for that leak. Magnesium is what the pump needs in order to hold potassium inside the cells. When magnesium runs low, the kidney lets potassium go regardless of how much you feed. A low potassium that will not come up is the classic sign that magnesium was never checked. Months of adding potassium to the bowl can pass with the number never moving.
Two other reasons food alone stalls out. Boiling and draining vegetables removes the potassium you were trying to add. And if your dog’s appetite has dropped, a richer bowl she eats less of does not deliver more.
Ask for magnesium on the next panel before you spend a season feeding into a leak.
Sub-Q fluids
If your dog is on fluids, this changes
Subcutaneous fluids are the most common intervention in canine kidney care, and almost nobody thinks of them as an electrolyte decision. They are one.
What comes out of the bag has a potassium concentration, and it is low. Lactated Ringer’s carries roughly 4 mEq/L. Normosol-R and Plasma-Lyte carry about 5. Plain saline carries none at all. All three sit at or below the bottom of a healthy dog’s serum range, which means the fluid going in is more dilute than the blood it joins.
For a dog already running low, that is a double hit. The fluid dilutes what is circulating, and the increased urine output that follows carries more potassium out the other end. A dog sitting at 3.6 before fluids can be at 3.1 after a few weeks of them, with no change to the food and no change to the disease. I have watched owners get told their kidney values improved and their potassium dropped, and hear those as two unrelated pieces of news. They are one piece of news.
For a dog running high, better hydration usually helps, since perfusion drives excretion. That only holds if the dog is producing urine. Fluids given to a dog who has stopped making urine put volume into a system with no exit.
Ask your vet before starting, and again if the schedule changes
Which fluid is in the bag, and what is its potassium concentration. Whether potassium should be added to it, and at what concentration. When to recheck electrolytes after starting, or after any change in frequency or volume.
Potassium can be added to a fluid bag, and for a chronically low dog it often should be. That is a prescription decision and a compounding decision, and it is not one to make at your kitchen counter. Concentrated potassium chloride is dangerous handled wrong, and added potassium stings going in under the skin, which affects whether your dog will tolerate the treatment at all. Both of those belong to your veterinarian.
The short version: if the fluid schedule changes, the potassium gets rechecked. Fluids are a treatment, and treatments move numbers.
The finding
Why every commercial renal diet adds potassium
Look at the ingredient panel of a therapeutic kidney diet, whether it is a prescription kibble or a fresh cooked renal formula. Somewhere in the list you will find potassium chloride, or potassium citrate, or both.
That is deliberate, and for most dogs it is correct. The typical chronic kidney disease patient wastes potassium, eats poorly, and runs acidotic. Added potassium replaces the renal losses. Potassium citrate does double duty by buffering the metabolic acidosis, since citrate converts to bicarbonate. If you were designing a food for the average kidney dog, you would add potassium too.
The dog these products do not fit is the one running high. She is being fed added potassium every day by a food that is otherwise right for her disease. The phosphorus control is right, the protein quality is right, and one ingredient is quietly pushing up the number that is already too high. I have not found a commercial product that gives you the renal phosphorus restriction without the potassium addition, which is why these cases end up formulated at home.
This has been studied
Segev and colleagues looked at dogs with chronic kidney disease whose potassium ran high while they were eating commercial renal diets. Moving them to a home-prepared diet with the potassium reduced brought the number back down. The study is small, and it is the reason I stopped treating a renal label as automatically safe for every kidney dog.
Fixing a high potassium can go too far. Potassium cannot go to zero.
AAFCO sets a minimum for a reason, and a dog on a binder, a diuretic, and an aggressive low-potassium bowl can be walked straight from one end of the range to the other. In the case that sent me down this road we held potassium in the moderate range rather than flooring it, precisely because there were three other forces already pulling downward. The target is the middle of the range, not the bottom of it.
The bowl
Where potassium hides in a home-cooked meal
For a dog whose kidney can clear normally, none of this needs managing. For a dog who cannot, here is the map. Values are milligrams per 100 grams, and every row says whether the food is raw or cooked.
Raw and cooked are not the same number, and the gap is large. Cauliflower is the clearest example. Raw it runs around 300mg per 100g. Boiled and drained it drops to about 140. Same vegetable, half the potassium, and the difference is only the cooking water you poured down the sink.
Which direction it moves depends on the method. Boiling pulls potassium out into the water. Roasting and steaming drive water off and leave the potassium behind, so the number per 100 grams goes up. If you compare a value here against one somewhere else and they disagree, check which state each is describing before assuming one is wrong.
Egg white deserves a note, because it gets oversold. Its real advantage in renal cooking is phosphorus, which is remarkably low for the protein it delivers. Its potassium is moderate rather than negligible. Useful, not magic.
Three of the highest-potassium greens carry a second problem. Swiss chard runs about 1,008mg of oxalate per 100g. Spinach about 750. Beet greens about 610. For a dog already forming calcium oxalate stones, or predisposed to them, that is a reason to leave these out even before you count the potassium.
I have not found clinical work setting an oxalate ceiling for dogs with kidney disease, so I treat this as a reason for caution rather than a rule with a number attached. I put the full potassium and oxalate figures for green vegetables in a separate table here.
Three places it gets in without anyone noticing
Salt substitutes
Lite salt and every no-sodium salt alternative is potassium chloride. A quarter teaspoon carries several hundred milligrams of potassium. It should never go anywhere near a dog who is running high.
All-in-one supplement premixes
Many balancers carry potassium chloride or potassium citrate in the mineral blend, listed in small print near the bottom. Bone meal and eggshell calcium do not carry potassium. Blended balancers often do. Read the full ingredient list before adding a premix to a renal recipe.
Treats
Dried sweet potato chews, banana slices, jerky, coconut water. On a seventeen pound dog, treats can be ten percent of the day’s intake, aimed at exactly the wrong mineral.
A technique worth learning. Potassium is water soluble. Dicing vegetables small, boiling them in a large volume of water, and discarding the water removes a substantial fraction of the potassium, well over half in the case of diced potato. The same applies to meat, though less dramatically, and boiling meat costs you some of the water-soluble B vitamins along with it. This is standard practice in human renal kitchens and it transfers cleanly to a dog’s bowl. It also runs in reverse: if you are trying to raise a low potassium, boiling and draining is working against you.
Formulation
Protein and phosphorus are two of about a dozen
Search kidney disease in dogs and you will find protein and phosphorus, and then you will find protein and phosphorus again. Both are real. Phosphorus restriction has the strongest evidence in the whole field for slowing progression, and protein quality and quantity decide whether your dog holds her muscle. I formulate for both, every time.
They are also two lines on a longer sheet. What a formulated bowl is holding at once:
- Phosphorus, and the calcium that has to be balanced against it
- Protein, set by amount and by biological value, which are separate decisions
- Potassium, set from your dog’s labs rather than from her diagnosis
- Sodium, because hypertension travels with kidney disease
- Magnesium, which the failing kidney clears poorly and which nobody looks at until it is high
- Copper, if there is anything going on with the liver
- EPA and DHA, which have real evidence behind them in proteinuric disease
- The acid load of the whole diet, since these dogs trend acidotic
- Fat, calories, and moisture, because a renal diet the dog will not eat is not a renal diet
Two dogs with the same stage of kidney disease can need opposite potassium targets. One is wasting it. The other cannot clear it. Feed either one the other one’s food and you make her worse.
There is no way to guess which dog is in front of you. The label on the bag cannot know it. Only the bloodwork knows it, which is why the bloodwork comes before the recipe, and why the recipe gets revisited every time the bloodwork moves.
Commercial diets are built for the average dog
A prescription renal diet is a good product. It has to work for thousands of dogs at once, so it is built for the dog in the middle: losing potassium, running acidic, losing muscle, needing phosphorus held down. For that dog it is the right answer, and I would not try to beat it at home.
The trouble starts when your dog is not that dog. Her potassium runs high instead of low. Her liver numbers change what you can do with copper. A history of pancreatitis caps how much fat she can have. She is on three drugs that each pull on a different mineral. There is no bag on the shelf built for her, because there are not enough dogs like her to make one for.
And you cannot fix it by picking a better ingredient, because the ingredients do not cooperate. Look at what is highest in potassium: spinach, chard, sardines, salmon, beef liver, lentils, sweet potato. Now look at what those same foods carry. Phosphorus, in almost every case. So an owner told her dog’s potassium is low reaches for exactly the foods she has been avoiding since the day of diagnosis. She fixes one number and breaks the other, and nothing on the label warned her the two were connected.
That is what formulation is for. Not because software is clever, but because when four minerals have to land inside four different windows at once, you need to see all four move every time you change one ingredient. Add the sweet potato, watch the phosphorus climb in the same window. Magnesium sits on that same sheet, so if it is low you find out before you spend three months feeding potassium into a leak.
A commercial diet answers the average question. Your dog may be asking a different one.
TCM Dietetics
The picture behind the number
Neither number appears in a classical text, and I am not going to pretend otherwise. What appears is the picture the number produces.
The low-potassium dog reads as Spleen qi deficiency, often with a yang deficient edge. Weak limbs, no push behind the movement, sluggish bowel, poor appetite, no transformation happening in the center. The direction there supports the center’s ability to transform and transport rather than reaching for more raw input, because a center that cannot transform will not use what you add.
The dog holding potassium she cannot clear reads as a failure of the Kidney’s separation of the clear from the turbid. What should be sent out is staying in. That picture asks for warmth and movement in the lower burner and a bowl that does not add to the load, rather than tonification piled on top of retained turbidity.
Both readings point the same direction as the bloodwork, which is a good sign the plan is aimed correctly.
Rechecks
Ask your vet how often, and write the answer down
There is no universal recheck interval, and any article that gives you one is guessing about your dog. The right cadence depends on how far out of range the number is, how fast it got there, and what is being changed. That is a conversation with your veterinarian, and it is worth having as an explicit question rather than assuming someone will raise it.
Ask it in this form: given where her potassium is right now, how often do you want to see her, and what would make you want to see her sooner.
The second half of that question is the one people forget to ask. Then ask again every time something changes, because the interval that was right at diagnosis is rarely still right three months later.
- A number further from the reference range
- Any change to an ACE inhibitor, an ARB, spironolactone, or a diuretic
- Starting sub-Q fluids, or changing the volume or frequency
- A change of diet
- Any stretch of vomiting, diarrhea, or reduced appetite
- A dog who is symptomatic, regardless of what the last number said
- A full chemistry with electrolytes, not a screening panel that leaves them off
- Sodium reported alongside potassium. High potassium next to low sodium is the Addison’s pattern and needs its own workup
- Magnesium, particularly in chronic kidney disease, and particularly if a potassium problem is not responding to what you are doing about it
- Whether the sample was hemolyzed, which you have to ask about because it will not always be flagged
An ECG belongs in the conversation any time potassium runs above the moderate range, or any time the heart rate is slow in a dog who is unwell.
Scope
All prescribing and all dosing sits with your veterinary team, including any decision about potassium supplements, binders, or what goes into a fluid bag. My work is the bowl. What I need from you is the labs, and what I need from the labs is the actual numbers rather than the word normal, because a potassium at the top of the range in a dog whose kidneys are failing is a different situation from one in the middle, even though both get called normal.
Where this leaves you
She slept through all of it
The number moved, the drug came off, the food changed, and she slept through every part of it on the same cushion in the same square of sun.
Nothing about her told me her potassium was 6.2. Not her coat, not her appetite, not how she got off the couch. The bloodwork told me, and the bloodwork is the only thing that ever will.
If your dog has kidney disease and you have never been told which way her potassium is drifting, that is the next question to ask. If you already know, and the commercial options are not fitting her, the recipe can be built around her actual numbers instead of around her diagnosis.
Ranges and food values are given for orientation and vary by laboratory, by source, and by whether the food is raw or cooked. Read your dog’s results against the reference interval printed on her own report, and make all treatment decisions with your veterinary team.
Hannah Zulueta obtained her Certificate in Canine Nutrition from CASI Institute. She is also studying for her Doctorate in Acupuncture, Traditional Chinese Medicine, and Herbalism from the esteemed Pacific College of Health and Medicine. If you’re as keenly interested in health for yourself, visit her website for human health: Satori Acupuncture and Herbs.
She resides in San Diego with her three dogs, Maggie, Orbit, and Mr. Higgins.
She is available for one on one consultations. She develops evidence-based recipes that meet both NRC and AAFCO nutritional standards while integrating the therapeutic food principles of Traditional Chinese Veterinary Medicine into her formulations.
Additionally, you can find her sharing free content on Instagram.
