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Hyperkalemia and other electrolyte changes: potassium, sodium and chloride

Hyperkalemia in a dog or cat is a potassium result above the lab's interval that most often comes from reduced urinary excretion, adrenal failure, a shift of potassium out of cells or the sample itself, and the sodium and chloride on the same panel help say which.

Reviewed by Brian Toncray, DVM ยท October 22, 2026

Electrolyte changes can kill quickly, and the underlying cause has to be found and corrected, with attention to how fast sodium in particular is moved back toward normal1. Potassium is the value that most often forces a decision in the first minutes, so it leads this page.

Potassium

High can mean
Reduced excretion through the urinary tract: urethral obstruction in male cats, where obstructive uropathy disturbs electrolytes and acid-base balance2, and a ruptured urinary tract, which should be suspected whenever azotemia, hyperkalemia and abdominal effusion appear together3. Hypoadrenocorticism: immune-mediated destruction of the adrenal cortex removes aldosterone and cortisol, producing the familiar hyperkalemia with hyponatremia; young female dogs are overrepresented4. Whipworm infection in dogs can produce electrolyte changes that look Addisonian with normal cortisol and aldosterone responses, a syndrome called pseudohypoadrenocorticism5. Potassium also moves out of cells with acidemia and with tissue damage, including reperfusion of a limb after aortic thromboembolism in cats.
Low can mean
Hypokalemia is common in cats with chronic kidney disease and is part of their routine monitoring6. Vomiting and diuretic therapy produce metabolic alkalosis in which potassium and chloride both need correcting7. Severe hypokalemia is an emergency in its own right1.
Can shift it artificially
Sample contamination and red cells. Carryover of potassium EDTA from a lavender-top tube raises potassium and lowers calcium, and a marked thrombocytosis can release potassium into serum as the sample clots. About a fifth of healthy Akitas in one study carried a high-potassium red cell phenotype with higher plasma potassium than other Akitas8. High-potassium red cells are also reported in Shibas, Jindos, other East Asian breeds and Chinese Shar Peis, where serum potassium can read high with no clinical signs of hyperkalemia9.
Next test
An ECG to see whether the heart is affected; bladder palpation and imaging in a cat that is straining or a patient after trauma; a check of breed, sample type and handling; an ACTH stimulation test when hypoadrenocorticism is suspected, which is the definitive test10; a fecal flotation in a dog with diarrhea and Addisonian electrolytes5.

Sodium

High can mean
Loss of water in excess of sodium, or salt gain, usually with restricted access to water. Signs come mainly from the central nervous system and are worse the faster the sodium rose11. In a large hospital population, hypernatremia carried a higher case fatality rate than a normal sodium in both dogs and cats, and the fatality rate climbed with severity12. Hospital care itself is a cause: among dogs and cats with moderate or severe hypernatremia in that study, half of the dogs and most of the cats developed it after admission12.
Low can mean
Hypoadrenocorticism in dogs, usually beside hyperkalemia4, and the whipworm-associated syndrome that copies it5. Whatever the cause, the speed of correction matters as much as the direction1.
Can shift it artificially
Lipemia and marked hyperproteinemia can produce a falsely low sodium on analyzers that dilute the sample before measuring (indirect ion-selective electrodes); a direct method on whole blood avoids it. Marked hyperglycemia lowers measured sodium by moving water into plasma, which is a real shift rather than an artifact.
Next test
Water access and intake history, urine specific gravity, and a planned rate of change rather than a target number1,11.

Chloride

High can mean
Hyperchloremic metabolic acidosis, which arises from chloride retention, sodium loss relative to chloride, or chloride gain relative to sodium13. A high chloride usually travels with metabolic acidosis because chloride and bicarbonate move in opposite directions14.
Low can mean
Metabolic alkalosis, most often from vomiting or diuretic therapy, in its chloride-responsive form7. A dog with months of intermittent vomiting from a partial mesenteric volvulus showed exactly this picture, a hypokalemic, hypochloremic metabolic alkalosis15.
Can shift it artificially
Water balance. Chloride moves with sodium, so a chloride change that simply mirrors sodium reflects water, not acid-base. The corrected chloride, calculated from measured chloride and sodium, separates a true chloride disorder from a water shift14.
Next test
Corrected chloride and a blood gas for bicarbonate and pH14.

Reading these values together

Hyperkalemia with hyponatremia is the textbook Addisonian pair, but it is not specific. Urethral obstruction, uroabdomen and trichuriasis can all reproduce it, and an azotemic Addisonian dog with dilute urine can be mistaken for primary kidney failure4,3,5. The reverse trap also exists: some dogs with hypoadrenocorticism lack only glucocorticoid and have normal electrolytes4. In a study of dogs with glucocorticoid-deficient disease and no electrolyte changes, a higher lymphocyte count and a lower albumin to globulin ratio discriminated best, yet no single value could rule the disease out without cortisol testing16.

Read chloride against sodium before calling it abnormal. When chloride falls further than sodium, look for vomiting of gastric contents or diuretics and expect a metabolic alkalosis; when it rises further, look for a hyperchloremic acidosis14,7,13. A potassium result that does not match the patient, in a breed with high-potassium red cells, is a sample question before it is a clinical one8,9.

Example: a panel worked through

Example. A 4-year-old spayed female mixed-breed dog has vomited on and off for two weeks and is now weak. Potassium is above the lab's interval, sodium and chloride are below it, BUN and creatinine are above it, USG is not concentrated and the lymphocyte count is at the top of the interval despite the illness.

This panel fits hypoadrenocorticism, and the dilute urine with azotemia is the pattern that makes it look like kidney failure4. An ECG comes first because of the potassium, then an ACTH stimulation test10. A fecal flotation goes in the same afternoon, since whipworm infection can produce this electrolyte picture with a normal adrenal axis5.

Frequently asked questions

What causes high potassium in a dog?

Reduced urinary excretion from obstruction or a ruptured urinary tract, hypoadrenocorticism, and occasionally a whipworm-associated syndrome that mimics it. A sample or breed effect is the other possibility2,3,4,5.

Can a high potassium be a lab artifact?

Yes. Akitas, Shibas, Jindos, other East Asian breeds and Shar Peis can carry red cells rich in potassium, giving a high serum result with no clinical hyperkalemia8,9.

Do normal sodium and potassium rule out Addison's disease?

No. Some dogs lack only glucocorticoid and keep normal electrolytes, and cortisol testing is needed to rule the disease out4,16.

What does a low chloride mean?

Usually metabolic alkalosis from vomiting or diuretics, once a simple water shift has been excluded with a corrected chloride7,14.

Sources

  1. Schaer M. Therapeutic approach to electrolyte emergencies. Vet Clin North Am Small Anim Pract. 2008; 38(3):513-33, x. PMID: 18402878. DOI: 10.1016/j.cvsm.2008.01.012.
  2. Bartges JW, Finco DR, Polzin DJ, et al. Pathophysiology of urethral obstruction. Vet Clin North Am Small Anim Pract. 1996; 26(2):255-64. PMID: 8711861.
  3. Stafford JR, Bartges JW. A clinical review of pathophysiology, diagnosis, and treatment of uroabdomen in the dog and cat. J Vet Emerg Crit Care (San Antonio). 2013; 23(2):216-29. PMID: 23470168. DOI: 10.1111/vec.12033.
  4. Klein SC, Peterson ME. Canine hypoadrenocorticism: part I. Can Vet J. 2010; 51(1):63-9. PMID: 20357943.
  5. Graves TK, Schall WD, Refsal K, et al. Basal and ACTH-stimulated plasma aldosterone concentrations are normal or increased in dogs with trichuriasis-associated pseudohypoadrenocorticism. J Vet Intern Med. 1994; 8(4):287-9. PMID: 7983625. DOI: 10.1111/j.1939-1676.1994.tb03234.x.
  6. Sparkes AH, Caney S, Chalhoub S, et al. ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease. J Feline Med Surg. 2016; 18(3):219-39. PMID: 26936494. DOI: 10.1177/1098612X16631234.
  7. Rabelo RC, Autran de Morais H. Quick Reference on Metabolic Alkalosis. Vet Clin North Am Small Anim Pract. 2026; 56(1):27-32. PMID: 41136256. DOI: 10.1016/j.cvsm.2025.09.023.
  8. Conrado FO, Oliveira ST, Lacerda LA, et al. Clinicopathologic and electrocardiographic features of Akita dogs with high and low erythrocyte potassium phenotypes. Vet Clin Pathol. 2014; 43(1):50-4. PMID: 24405428. DOI: 10.1111/vcp.12112.
  9. Battison A. Apparent pseudohyperkalemia in a Chinese Shar Pei dog. Vet Clin Pathol. 2007; 36(1):89-93. PMID: 17311201. DOI: 10.1111/j.1939-165x.2007.tb00188.x.
  10. Klein SC, Peterson ME. Canine hypoadrenocorticism: part II. Can Vet J. 2010; 51(2):179-84. PMID: 20436864.
  11. Guillaumin J, DiBartola SP. A Quick Reference on Hypernatremia. Vet Clin North Am Small Anim Pract. 2017; 47(2):209-212. PMID: 28164834. DOI: 10.1016/j.cvsm.2016.10.002.
  12. Ueda Y, Hopper K, Epstein SE. Incidence, severity and prognosis associated with hypernatremia in dogs and cats. J Vet Intern Med. 2015; 29(3):794-800. PMID: 25996661. DOI: 10.1111/jvim.12582.
  13. Martiny PM, de Morais HA. A Quick Reference on Hyperchloremic Metabolic Acidosis. Vet Clin North Am Small Anim Pract. 2026; 56(1):33-38. PMID: 41136257. DOI: 10.1016/j.cvsm.2025.09.005.
  14. Ueda Y. A Quick Reference on Chloride. Vet Clin North Am Small Anim Pract. 2026; 56(1):57-65. PMID: 41087250. DOI: 10.1016/j.cvsm.2025.09.008.
  15. Spevakow AB, Nibblett BM, Carr AP, et al. Chronic mesenteric volvulus in a dog. Can Vet J. 2010; 51(1):85-8. PMID: 20357947. DOI: 10.4141/cjas71-011.
  16. Reagan KL, McLarty E, Marks SL, et al. Characterization of clinicopathologic and abdominal ultrasound findings in dogs with glucocorticoid deficient hypoadrenocorticism. J Vet Intern Med. 2022; 36(6):1947-1957. PMID: 36326216. DOI: 10.1111/jvim.16564.