Hypokalemia (low potassium) is a common and often under-recognized issue in cats with chronic kidney disease (CKD), and it can significantly affect strength, hydration status, and quality of life.
Hypokalemia means that the potassium level measured in the blood is below normal, usually under about 3.5 mmol/L. What’s important to understand is that blood potassium only tells part of the story. More than 95% of a cat’s total potassium lives inside cells, not in the bloodstream, where it plays a critical role in maintaining normal nerve and muscle function. Because of this, a cat can have a “mildly low” or even normal blood potassium level while still being significantly depleted overall.
In healthy cats eating a balanced diet, potassium intake is usually more than adequate, and excess potassium is eliminated through the kidneys. The hormone aldosterone tightly controls this process. When blood volume drops, aldosterone levels rise, causing the kidneys to retain sodium and excrete potassium. Potassium itself also influences aldosterone release - high potassium stimulates aldosterone, while low potassium suppresses it.
Acid–base balance adds another layer of complexity. Acidosis tends to raise blood potassium, while alkalosis lowers it, both by shifting potassium in and out of cells and by increasing urinary potassium loss.
Most cases of hypokalemia are caused either by actual potassium loss or by potassium shifting from the bloodstream into cells. Poor dietary intake alone is rarely the cause, although acidifying diets that are low in potassium have been linked to significant potassium depletion in cats. Mild hypokalemia is common and often overlooked, but it can still reflect substantial total-body depletion. Once potassium drops below about 3.0 mmol/L, treatment becomes important, and levels below 2.5 mmol/L are a true medical emergency.
Potassium loss can occur through the gastrointestinal tract or the kidneys. Vomiting and diarrhea remove potassium directly, and conditions like gastric outflow obstruction can worsen hypokalemia by creating metabolic alkalosis, which drives potassium into cells and increases urinary losses. Kidney-related potassium loss is especially relevant in cats with chronic kidney disease. Even though the kidneys normally regulate potassium well, CKD cats often lose excessive potassium in urine, particularly if they are polyuric. Post-obstructive diuresis, certain renal tubular disorders, and rare conditions like primary hyperaldosteronism can also cause profound potassium wasting.
Medical treatment itself can contribute. Cats receiving IV fluids without added potassium, especially if they are anorexic, can become progressively depleted. Diuretics can also increase urinary potassium loss.
Low potassium has real, visible consequences. As potassium drops, muscle cells become less excitable, leading to weakness. In cats, this often shows up as difficulty jumping or the classic cervical ventroflexion posture, where the head hangs downward. Hypokalemia also interferes with the kidney’s ability to concentrate urine by impairing the response to antidiuretic hormone, which can worsen excessive urination and thirst. Severe hypokalemia can progress to generalized muscle paralysis, including the muscles responsible for breathing, and can be fatal if not corrected.
Although chronic hypokalemia has been shown in experimental studies to affect kidney structure and blood vessel formation, low potassium itself is not currently considered a driver of CKD progression in cats. Still, it clearly worsens quality of life and complicates disease management.
Evaluating a hypokalemic cat means looking beyond the potassium number. History, physical exam findings, kidney values, urine concentration, blood pressure, acid–base status, and sometimes hormone testing are all important for identifying the underlying cause. Treatment depends on severity. Mild cases can often be managed with oral potassium supplementation, while more severe cases require carefully monitored IV potassium replacement. Refractory cases may need magnesium supplementation, since magnesium deficiency can prevent potassium from being retained even when supplementation is aggressive.
The key takeaway is that hypokalemia is common, multifactorial, and often under-recognized — especially in cats with CKD. Even mild decreases in blood potassium can mask significant total-body depletion, and careful monitoring and thoughtful supplementation with your veterinarian’s guidance are essential to prevent serious complications.
Sources:
Evaluation and Management of the Hypokalemic Patient
Retrospective study of the efficacy of oral potassium supplementation in cats with kidney disease - PubMed
Dietary Management of Feline Chronic Renal Failure: Where are We Now? In What Direction are We Headed? - PMC
Hypokalemia in Feline Chronic Kidney Disease
Hypokalemia means that the potassium level measured in the blood is below normal, usually under about 3.5 mmol/L. What’s important to understand is that blood potassium only tells part of the story. More than 95% of a cat’s total potassium lives inside cells, not in the bloodstream, where it plays a critical role in maintaining normal nerve and muscle function. Because of this, a cat can have a “mildly low” or even normal blood potassium level while still being significantly depleted overall.
In healthy cats eating a balanced diet, potassium intake is usually more than adequate, and excess potassium is eliminated through the kidneys. The hormone aldosterone tightly controls this process. When blood volume drops, aldosterone levels rise, causing the kidneys to retain sodium and excrete potassium. Potassium itself also influences aldosterone release - high potassium stimulates aldosterone, while low potassium suppresses it.
Acid–base balance adds another layer of complexity. Acidosis tends to raise blood potassium, while alkalosis lowers it, both by shifting potassium in and out of cells and by increasing urinary potassium loss.
Most cases of hypokalemia are caused either by actual potassium loss or by potassium shifting from the bloodstream into cells. Poor dietary intake alone is rarely the cause, although acidifying diets that are low in potassium have been linked to significant potassium depletion in cats. Mild hypokalemia is common and often overlooked, but it can still reflect substantial total-body depletion. Once potassium drops below about 3.0 mmol/L, treatment becomes important, and levels below 2.5 mmol/L are a true medical emergency.
Potassium loss can occur through the gastrointestinal tract or the kidneys. Vomiting and diarrhea remove potassium directly, and conditions like gastric outflow obstruction can worsen hypokalemia by creating metabolic alkalosis, which drives potassium into cells and increases urinary losses. Kidney-related potassium loss is especially relevant in cats with chronic kidney disease. Even though the kidneys normally regulate potassium well, CKD cats often lose excessive potassium in urine, particularly if they are polyuric. Post-obstructive diuresis, certain renal tubular disorders, and rare conditions like primary hyperaldosteronism can also cause profound potassium wasting.
Medical treatment itself can contribute. Cats receiving IV fluids without added potassium, especially if they are anorexic, can become progressively depleted. Diuretics can also increase urinary potassium loss.
Low potassium has real, visible consequences. As potassium drops, muscle cells become less excitable, leading to weakness. In cats, this often shows up as difficulty jumping or the classic cervical ventroflexion posture, where the head hangs downward. Hypokalemia also interferes with the kidney’s ability to concentrate urine by impairing the response to antidiuretic hormone, which can worsen excessive urination and thirst. Severe hypokalemia can progress to generalized muscle paralysis, including the muscles responsible for breathing, and can be fatal if not corrected.
Although chronic hypokalemia has been shown in experimental studies to affect kidney structure and blood vessel formation, low potassium itself is not currently considered a driver of CKD progression in cats. Still, it clearly worsens quality of life and complicates disease management.
Evaluating a hypokalemic cat means looking beyond the potassium number. History, physical exam findings, kidney values, urine concentration, blood pressure, acid–base status, and sometimes hormone testing are all important for identifying the underlying cause. Treatment depends on severity. Mild cases can often be managed with oral potassium supplementation, while more severe cases require carefully monitored IV potassium replacement. Refractory cases may need magnesium supplementation, since magnesium deficiency can prevent potassium from being retained even when supplementation is aggressive.
The key takeaway is that hypokalemia is common, multifactorial, and often under-recognized — especially in cats with CKD. Even mild decreases in blood potassium can mask significant total-body depletion, and careful monitoring and thoughtful supplementation with your veterinarian’s guidance are essential to prevent serious complications.
Sources:
Evaluation and Management of the Hypokalemic Patient
Retrospective study of the efficacy of oral potassium supplementation in cats with kidney disease - PubMed
Dietary Management of Feline Chronic Renal Failure: Where are We Now? In What Direction are We Headed? - PMC
Hypokalemia in Feline Chronic Kidney Disease