Nutrition & Nutrients

Sodium in dogs: function, requirements, and hyponatremia

Sodium (Na⁺) is the most important extracellular cation and an essential macromineral. It regulates osmotic pressure, extracellular fluid volume, and acid-base balance. Together with potassium (K⁺), sodium controls nerve and muscle impulse conduction via the sodium-potassium ATPase.

Sodium in dogs: function, requirements, and hyponatremia

What is sodium in dogs?

Sodium (Na⁺) is the most important extracellular cation and an essential macromineral. It regulates osmotic pressure, extracellular fluid volume, and acid-base balance. Together with potassium (K⁺), sodium controls impulse conduction in nerves and muscles via the sodium-potassium ATPase.

Sodium enters the body through food and is excreted via the kidneys — renal sodium regulation is a central mechanism in blood pressure control. A balanced sodium status is essential for stable hemodynamics, neurology, and hydration.

Background + scientific context

NRC (2006, Nutrient Requirements of Dogs and Cats) defines sodium requirements: AAFCO minimum for adult dogs: 200 mg/kg dry matter (DM). NRC recommendation: 370 mg/kg DM. A defined upper limit for healthy dogs is difficult to establish — in the short term, healthy dogs tolerate high amounts of sodium (renal excretion), but with impaired kidney function or heart disease, excessive sodium can become clinically problematic. Sodium and chloride are regulated as an electrolyte pair — chloride deficiency also alters sodium balance.

Fascetti and Delaney (2012, Applied Veterinary Clinical Nutrition) describe nutritional therapy aspects: In heart disease and chronic kidney insufficiency, sodium-reduced food is recommended — high sodium intake increases preload and worsens heart function in dogs with pre-existing heart failure. The sodium content in commercial therapeutic diets for heart and kidney patients is significantly below the level found in standard foods. BARF diets consisting mainly of muscle meat contain sufficient sodium — specific supplementation is unnecessary.

Ettinger et al. (2017, Textbook of Veterinary Internal Medicine) describe the diagnostic significance of the sodium-potassium ratio in hypoadrenocorticism (Addison’s disease): Primary Addison’s disease causes sodium loss and potassium retention due to a deficiency of mineralocorticoid (aldosterone) — clinical picture: hyponatremia (Na⁺ < 135 mmol/l), hyperkalemia (K⁺ > 5.5 mmol/l), Na:K ratio < 27:1. This electrolyte finding is considered the diagnostic fingerprint of a dog with Addison’s disease and forms the screening basis before the ACTH stimulation test. Hypernatremia (Na⁺ > 155 mmol/l) occurs with dehydration or excessive salt intake and is less common, but potentially dangerous (cerebral symptoms).

Vitomalia position

Sodium in commercially produced food is formulated to meet requirements. Sodium becomes clinically relevant in heart disease (restriction), kidney disease (restriction), and in dogs with Addison’s disease (diagnostics). Large amounts of table salt are toxic to dogs — table salt is not a Supplement.

When does sodium become relevant?

  • Heart disease: prescription sodium-reduced food is recommended
  • Chronic kidney disease: monitor sodium in the food
  • Weakness, vomiting, collapse: rule out Addison’s disease (measure Na:K ratio)
  • BARF: never supplement table salt — animal products cover the requirement
  • Heat collapse / intense endurance exercise: check electrolyte balance incl. sodium

Practical use

Sodium status — clinical interpretation:

Finding Serum value Possible cause
Normonatremia 140–155 mmol/l Normal finding
Hyponatremia < 135 mmol/l Addison’s disease, heart failure, water intoxication
Hypernatremia > 155 mmol/l Dehydration, excessive salt intake

Addison’s screening — electrolyte pattern: - Na⁺ < 135 mmol/l - K⁺ > 5.5 mmol/l - Na:K ratio < 27:1 - Confirmation: ACTH stimulation test (cortisol response)

Sodium content in typical food sources:

Source Sodium (mg/100g) Assessment
Beef (muscle meat) 55–75 mg Sufficient
Chicken meat 70–80 mg Sufficient
Standard dry food 400–600 mg Meets requirements
Cardiac diet food 200–300 mg Reduced
Table salt (NaCl) 38,600 mg Never supplement

Common mistakes & myths

  • “A little salt in the food won’t hurt.” Occasional small amounts of table salt are not an acute problem for healthy dogs. Regular addition or large amounts — especially in small breeds, or dogs with heart or kidney disease — is harmful. Excess sodium increases thirst and puts strain on the kidneys and heart.
  • “BARF contains too little sodium.” Muscle meat contains sufficient sodium for dog supplies. Additional table salt in BARF is contraindicated, not recommended.
  • “You notice Addison's disease straight away.” Chronic Addison's disease can progress for years with non-specific symptoms (lethargy, vomiting, weight loss). Addisonian shock (Addisonian crisis) is an acute emergency. Regular electrolyte checks are advisable for predisposed breeds.

State of research 2026

Sodium metabolism in dogs is well characterized. Diagnosing Addison's disease via the Na:K ratio is a veterinary standard. Current debates concern optimal sodium limits in cardiac diet foods — overly strict restriction can be counterproductive if the renin-angiotensin-aldosterone system is stimulated by low sodium intake. Dietary recommendations for heart disease are reviewed regularly.

Frequently asked questions

Is table salt toxic to dogs?

Yes, in large amounts — sodium chloride can cause hypernatremia, water loss from nerve cells, and neurological symptoms in dogs. Occasional contact (one salty chip) is harmless, but regular addition or large single amounts are dangerous.

What does a low sodium level mean in dogs?

Hyponatremia (Na⁺ < 135 mmol/l) combined with a high potassium level is a warning sign of Addison's disease. Other causes include chronic heart failure, severe diarrhea, and water intoxication. Veterinary assessment with an ACTH stimulation test is recommended if Addison's disease is suspected.

Does my dog need low-sodium food?

Only for specific diseases: heart disease (especially congestive heart failure) and advanced kidney disease. Healthy dogs do not benefit from sodium reduction — standard complete foods are correctly formulated.

Related terms

Sources & further reading

  1. National Research Council (NRC). (2006). Nutrient Requirements of Dogs and Cats. National Academies Press. ISBN 9780309086288.

  2. Fascetti, A. J., & Delaney, S. J. (Eds.) (2012). Applied Veterinary Clinical Nutrition. Wiley-Blackwell. ISBN 9780813815688.

  3. Ettinger, S. J., Feldman, E. C., & Côté, E. (Eds.) (2017). Textbook of Veterinary Internal Medicine (8th ed.). Saunders. ISBN 9780323312110.

Wissenschaftliche Einordnung

NRC (2006, Nutrient Requirements of Dogs and Cats) defines sodium requirements: AAFCO minimum for adult dogs: 200 mg/kg dry matter (DM). NRC recommendation: 370 mg/kg DM. A defined upper limit for healthy dogs is difficult to establish—healthy dogs tolerate high sodium levels short-term (renal excretion), but excessive sodium can become clinically problematic with impaired kidney function or heart disease. Sodium and chloride are regulated as an electrolyte pair—chloride deficiency also alters sodium balance.

Fascetti and Delaney (2012, Applied Veterinary Clinical Nutrition) describe nutritional therapeutic aspects: For heart disease and chronic renal insufficiency, reduced-sodium food is recommended—high sodium intake increases preload and worsens heart function in pre-existing heart failure. Sodium content in commercial diet foods for heart and kidney patients is significantly below standard food content. BARF with predominantly muscle meat contains sufficient sodium—specific supplementation is unnecessary.

Ettinger et al. (2017, Textbook of Veterinary Internal Medicine) describe the diagnostic significance of the sodium-potassium ratio in hypoadrenocorticism (Addison's disease): Primary Addison's disease leads to sodium loss and potassium retention due to mineralocorticoid (aldosterone) deficiency—clinical picture: hyponatremia (Na⁺ < 135 mmol/l), hyperkalemia (K⁺ > 5.5 mmol/l), Na:K ratio < 27:1. This electrolyte finding is considered a diagnostic fingerprint of an Addisonian dog and forms the basis for screening before an ACTH stimulation test. Hypernatremia (Na⁺ > 155 mmol/l) occurs with dehydration or excessive salt intake and is rarer but potentially dangerous (cerebral symptoms).