Ask Dr. Debra: Hypernatremia in Senior Cats

This Week’s Question:

Our 14-year-old cat has been diagnosed with hypernatremia. He has always liked drinking from the faucet, but now he wants to do it almost every 30 minutes, and even wakes us up at night to turn the faucet on for him. He will not drink from a water bowl or fountain.

Two vets don’t know why he has excessive sodium in his blood, and we know for a fact that he has not gotten into anything.

Is there anything else we can do for him? What would cause this?

Lisa Caputo

Dr. Debra’s Answer:

Hi Lisa,

Thanks for your question about high blood sodium level (hypernatremia) in senior cats.

I’m so sorry you are dealing with this complicated problem. Sodium is an electrolyte and considered elevated if above 155 mEq/L. A general article about low and high sodium levels can be found here.

There are several different reasons cats can have high blood sodium. The most common reasons don’t seem to fit with your cat’s situation, which include salt poisoning, decreased water intake or lack of access to water, high sodium intake, complications from fluid or drug therapy, or sodium loss from vomiting, diarrhea, or excessive urination.

Other Potential Causes of Hypernatremia

There are various regulating systems that balance electrolytes in the body very closely. When any part of the system is broken, electrolytes like sodium can be altered. One possibility for your cat’s problem would be diabetes insipidus (DI), although this is an uncommon disorder in cats. This isn’t the “high blood sugar type” of diabetes, but a type that results from inadequate production or release of a substance called ADH (antidiuretic hormone). In this disease, either the ADH isn’t being produced or the kidneys don’t respond to it correctly. It is such an uncommon problem (but it does happen) that we only have an article on DI in dogs.

Other possible causes for hypernatremia include some brain-related issues, including central nervous system lymphoma, hydrocephalus, and hypothalamic granulomatous meningoencephalitis.

It sounds like your veterinarian has worked hard to get you a diagnosis. At this point, it might be worth visiting a veterinary internal medicine specialist. Being a specialist means that after veterinary school, they went through 4 to 5 more years of training to help diagnose complex situations, like your cat’s. They also have access to specialized equipment to help evaluate kidney function and look for brain disease, such as ultrasound, MRI, CT, and much more.

Best of luck to you and your pet! Please let me know what happens.

With warm regards,

Dr. Debra

Please note: Dr. Debra’s guidance should not be considered veterinary advice like that provided by your veterinarian, since she is unable to personally examine your pet. If you have an immediate concern or emergency, contact a veterinarian or local veterinary hospital about your specific situation.