High Sodium in Dogs (Hypernatremia) Causes and Symptoms

Sodium is an essential mineral for dogs. It helps keep blood and fluid volume, maintain body fluid balance (inside and outside cells), electrolyte balance, helps nerve signal transfer, heart and muscle function, and balancing body pH, among many other roles.  See sodium functions and requirements in dogs.

Whereas it is essential, dogs must maintain a narrow range of sodium ions (Na+) concentration in the blood plasma of about 140-149 mE/L (mmol/L).

If this concentration goes beyond 150 mE/L, this animal will suffer from sodium poisoning or toxicity; a phenomenon referred to as hypernatremia. Sometimes, people call it salt poisoning since the alteration of sodium accompanies a change in chloride.

On the other hand, if Na+ concentration in blood plasma goes below 140 mE/L, your dogs will suffer from hyponatremia (low sodium in blood plasma) that will be characterized by several symptoms.

Understanding hypernatremia in dogs

To understand hypernatremia, including cause and symptoms, you deserve to know that most of the sodium in dogs is restricted to extracellular fluids (total water body) made of mainly interstitial fluid and blood plasma.

Therefore, when its level goes high, water will be drawn from cells due to the higher osmotic pressure created in the extracellular fluids. As water moves out of the cells, they will begin to shrink (crenate) and result in various symptoms with serious ones, including neurological ones occurring in the case of intracranial hemorrhage.

High sodium in dogs
High sodium in dogs

Types and causes

There are three types of hypernatremia grouped in terms of whether there is an increase, decrease, or no change in fluid volume, which are:

  • Hypovolemic hypernatremia – It occurs when both extracellular fluids volume and sodium decreases, but there is more water loss than there is to Na+.
  • Euvolemic hypernatremia – In this type, their body loses pure water creating a sodium-water imbalance while total fluid volume appears to be more or less the same.
  • Hypervolemic hypernatremia – It is characterized by both rise in total body water with a more significant Na+ increase. It may result in pulmonary edema if water moves from the cell and collects at the lung interstitium.

In perfect health, while under regular commercial diet and water drinking, dogs can regulate dietary sodium without causing a rise in their body. However, for one or another reason, they may fail to control sodium leading to poisoning. Common causes of hypernatremia in dogs and they include:

  • Not drinking water due to a defective body thirst mechanisms or absence of water due to frozen water source, broken automatic waterers.
  • Salt poisoning in case your dog ingest salt, saltwater, play dough, rock salt (sodium chloride ice melts), or any other substance high in salt or sodium. Furthermore, although it doesn’t work, some people use salt to induce vomiting.
  • The administration of fluids high in sodium (hypertonic saline solution) as well as the use of IV sodium bicarbonate to resuscitate dogs.
  • Ingestion of paintball (have polyethylene glycol and sorbitol) that will cause hypernatremia
  • Central diabetes insipidus due to decreased or absence of arginine vasopressin AVP (an antidiuretic hormone) that makes it hard for the kidney to conserve water by concentrating urine, hence a lot of water is lost.
  • Nephrogenic diabetes insipidus where renal tubular are impaired or cannot respond to AVP.
  • Pure water loss via excessive sweating, lungs (in a hot climate during as the dog is breathing), heatstroke, respiratory infections, third space losses, or any other reason.
  • Crushing’s disease (hyperaldosteronism).
  • Essential hypernatremia where faulty osmoreceptors that fail to recognize a sodium rise and takes it as usual.
  • Hypertonic fluid loss via diarrhea or vomiting or any other way.
  • Foods very high in salt fed without water.


At levels of plasma Na+ levels of 154 mEq/L, your dog will start showing signs. If the amount beyond 170 mEq/L, the condition becomes life-threatening.

Symptoms of sodium poisoning will range from gastrointestinal to neurological to cardiovascular, and they will depend on the severity of the poisoning and cause. Common ones include:

  • Lethargy
  • Poor appetites, nausea, vomiting, and diarrhea
  • elevated body temperatures
  • Extreme thirst, increase water consumption and urination
  • Inappropriate vocalization
  • Headache
  • Increased heartbeats
  • Difficulties in breathing
  • Neurological symptoms like confusion, dizziness, tremors, depression disorientation, fainting, seizures, as well as muscle stiffness, shaking, and jerking (myoclonus). Also, they suffer from neurological damage and go into a coma.
  • Death
  • Other symptoms related to the underlying cause like stomach pain if much salt was ingested.


Diagnosis will involve a look at patient history, physical examination, and tests like looking at your dog’s body temperature, pulse rate, reflexes, blood pressure, respiration, as well as quick hearing, and vision tests.

Afterward, your vet will go to more definitive tests that include urinalysis, complete blood count, metabolic panel, and conduct radiographs (ultrasound, CT scans, MRI, or X-rays) to check for any organ damage, especially brain, heart, or lungs.

Also, there may be complete cardiac diagnostic such as the use of electrocardiogram (EKG) to confirm if heart impulses are ok.  

All these tests will indicate sodium level in blood and body, find the underlying cause, and if there is any organ damage.


Treatment will include the stabilization of dogs with neurological signs, fluid therapy to correct electrolyte and fluid derangement. Administration of fluids will occur slowly as your vet monitors sodium levels. Rapid blood plasma Na+ change levels may cause cerebral edema or heart attack.

In the case of cerebral edema, your vet may recommend corticosteroid like dexamethasone to minimize inflammation.

Finally, your vet will treat the underlying where applicable.

Living management

If there is no significant organ damage, including the brain, liver, or heart, the prognosis is good. However, you will need continuous monitoring of your dog for any signs of sodium poisoning and routine tests to confirm if the levels are normal.

Furthermore, depending on the cause, your vet may recommend low sodium dog food as well as ask you to avoid any salty dog treats or human foods high in sodium. Such foods include bacon, sausages, cured ham, crisps, chips, cheese, beef jerkies, table scraps, and so on.

See also

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