Why a pea-sized bite is serious for a 3 kg cat
Rodent bait blocks are concentrated to kill rodents quickly, meaning even a tiny amount like a pea can be dangerous for a small cat. The green color often attracts pets, making accidental ingestion more likely. Your cat's senior status doesn't reduce the risk—age may actually make organ damage harder to recover from.
Anticoagulant rodenticides work by preventing blood clotting, so symptoms won't appear immediately. By the time you notice weakness or pale gums, internal bleeding may already be severe. The fact your cat seems fine now is deceptive—this is when treatment is most effective.
The delayed danger of anticoagulant poisoning
Unlike other toxins that cause vomiting or drooling right away, this type works silently over 2-5 days. The bait's sweet taste masks its danger, and cats rarely show discomfort initially. That single bite has likely already begun affecting vitamin K-dependent clotting factors in your cat's liver.
Waiting for visible signs like nosebleeds or limping means waiting until blood loss is advanced. At 3 kg, your cat has minimal reserves—a tablespoon of internal bleeding could be life-threatening. Emergency vets can administer vitamin K1 (the specific antidote) before symptoms start.
Why size matters more than amount eaten
A pea-sized piece might seem insignificant, but for a 3 kg animal, it's a substantial dose. Rodenticides are calculated by milligram per kilogram of body weight—what's a lethal dose for a rat is proportionally worse for a lighter cat. The bait's formulation ensures even reluctant nibblers consume enough to be fatal.
Smaller bodies process toxins differently—their livers may not metabolize the poison as efficiently as larger animals. Your cat's weight puts her in the highest risk category, where immediate intervention is critical regardless of the amount ingested.
What to do in the next 12 hours
Contact an emergency vet immediately, even if it's the middle of the night. Time is crucial—vitamin K1 therapy works best when started early. Bring the bait packaging if possible; the active ingredient (like brodifacoum or difenacoum) determines treatment duration.
Your vet will likely recommend blood tests to check clotting times and begin vitamin K1 injections. Expect a 30-day treatment plan—this poison has a long half-life. Monitor for subtle changes like reluctance to jump or faster breathing, which can precede collapse.
The step-by-step response, from the first minute to the vet visit, is in our Anticoagulant Rodenticide Toxicity in Dogs and Cats emergency guide.