Poisoning by Hypercalcemic Agents and Their Treatments in Cats

By PetMD Editorial on Apr. 6, 2009

Hypercalcemic Agent Poisoning in Cats

Of the various types of substances that are poisonous to animals, there are those that include hypercalcemic agents. Hypercalcemic agents contain vitamin D, medically known as cholecalciferol, which works by raising the calcium content in blood serum to high toxic levels, resulting in cardiac arrhythmias, and eventually, death. The condition of hypercalcemia is defined as an abnormally elevated level of calcium in the blood.

Hypercalcemic agents are popular for use in rodent poisons, since rodents do not have resistance to cholecalciferol. In most cases, poisons containing cholecalciferol must be directly consumed by an animal for it to fall ill. The exception to this is when a poisoned rodent is ingested by another animal.

Cats that have consumed hypercalcemic poisons typically will not show immediate symptoms. Symptoms of poisoning may show 18 to 36 hours after the cholecalciferol containing poison was consumed. Left untreated, a cat can die from cholecalciferol poisoning and the resulting hypercalcemia. For the cat that does survive, it will continue to have elevated calcium levels for weeks after the poisoning, and this excess of calcium can lead to secondary health problems, such as renal (kidney) failure.


  • Increased thirst
  • Frequent urination
  • Vomiting
  • Generalized weakness
  • Muscle spasms
  • Seizures
  • Fatigue
  • Elevated blood serum calcium


  • Ingestion of rodent poisons, or, ingestion of the rodent that ingested the poison
  • Any poison that contains hypercalcemic agents

The main cause of hypercalcemic poisoning is from the ingestion of rodent poison. If you suspect that your cat has come into contact with rat or mouse poison, and you are seeing some of the symptoms listed above, you will need to have your cat seen by a doctor before its health becomes critical. Keep in mind that if your cat goes out of doors at all there is the possibility that it will come into contact with rodent poisons. The poison might be in a neighbor's yard, in a trash bag, in an alleyway, or the poison might have been ingested by a rat or mouse that your cat has caught and ingested parts from. Even if you do not live in an area where rats or mice are a concern, rodent poison may be used for other common suburban pests, like raccoons, opossums, or squirrels.


Your veterinarian will perform a thorough physical exam on your cat, taking into account your cat's background medical history, onset of symptoms, and possible incidents that precipitated this condition. A complete blood profile will be conducted, including a chemical blood profile, and a complete blood count. Your veterinarian will conduct a blood test to check your cat's calcium levels and to confirm the presence of poison. If possible, you should take a sample of your cat's vomit with you to the veterinarian, so that it can also be examined for the presence of poison. If you actually have the poison that your cat ingested, you should take that to your doctor as well.


One of the side effects of hypercalcemic poisoning is dehydration, which can lead to organ failure and seizures. You will need to make sure that your cat is getting plenty of water, and that it is actually able to retain the water it is taking in (i.e., not vomiting it back up). Adding a small amount of salt to the water you are giving to your cat will encourage fluid retention, since increased salt can both help to increase or maintain body fluid, and induce normal excretion by the kidney. Your veterinarian will work on correcting your cat's body fluids, electrolyte imbalances, and calcium levels using diuretics, prednisone, and oral phosphorus binders, along with a low calcium diet.

Living and Management

Animals that have survived poisoning due to hypercalcemic agents may continue to experience long term side effects due to the high level of calcium in the blood, and in the body's organs. The kidneys are commonly damaged as a result of hypercalcemia.


The best prevention is to keep rodent poisons placed in areas that are not accessible to your cat, and to supervise your cat so that it does not get hold of a rodent that may have ingested poison containing a hypercalcemic agent. If you observe your cat with a rodent, try to get the rodent away from your cat before it is able to ingest a substantial amount of it.

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