Rat (Rodenticide) Poisoning in Cats

Rat and mouse poisoning occur when the cat either directly ingests rat poison or indirectly ingests it after catching and consuming a rodent that has itself ingested poison. Many rat and mouse poisons contain anticoagulants which inhibit the coagulation of blood. Internal bleeding occurs due to the poison which blocks the body’s production of clotting factors.

What causes internal bleeding?

Blood vessels are tubes that transport blood around the body; endothelial cells line the vessel walls which help blood travel efficiently through them. If the blood vessel breaks, three mechanisms occur to slow and stop the loss of blood.

  • Vasoconstriction: Small muscles in the blood vessel wall constrict which reduces the amount of blood flow, reducing blood loss.
  • Primary hemostasis: Platelets are circulating cells are activated, which clump together and bind to the site on the damaged blood vessel, to form a plug.
  • Secondary hemostasis (also known as coagulation cascade): The liver manufactures coagulation factors which are proteins that help to control bleeding. A complex set of chemical reactions occurs involving coagulation factors, converting factor 1 (fibrinogen) into fibrin, long thin strands which entangle the platelets.

Rat poison depletes the body of Vitamin K which is necessary for the formation of certain blood clotting factors.

Types of rat poison:

  • First-generation rat poisons have a shorter half-life, which is the time it takes for the poison to decrease by half. The active ingredient in first-generation rat poisons is Warfarin. Poisoning occurs after several repeated exposures.
  • Second generation rat poisons are considerably more potent and. The active ingredients in second-generation rat poisons are usually bromadiolone or brodifacoum. A single dose is enough to kill a cat.


The poisons do not affect clotting factors already in circulation, so there will be a lag of 1-3 days before these clotting factors run out (and are not replaced) and symptoms occur.

Not all cats who have ingested rat poison will display symptoms.


A history of exposure to rat poison, if possible. Bleeding from several places will also suggest to your veterinarian there is a blood clotting problem.

Your veterinarian may wish to perform some tests, which include blood tests to determine blood clotting time ACT, PT, and APTT tests.


If you suspect your cat has ingested rat poison, take your cat to a veterinarian immediately. If possible, bring along the packet to help with identification of the toxin.

Treatment will include:

  • If ingestion has occurred recently, then your veterinarian will induce vomiting and pump the stomach.
  • Activated charcoal binds to the toxin, preventing further absorption.
  • Vitamin K injection will help to form clotting factors.
  • If bleeding is severe, your cat may require a blood transfusion.
  • Once your cat is stable, he will be sent home with an oral dose of Vitamin K the cat will take for 30-45 days.
  • Supportive care such as intravenous fluids and nutritional support.

Julia Wilson is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. She enjoys photography, gardening and running in her spare time. Full author bio Contact Julia