Anticoagulant rat poison is the quietest emergency on this site. A cat that ate bait 3 hours ago looks completely normal, and it will keep looking normal for another 45 hours while its clotting factors run down. Bleeding starts 48 to 72 hours after ingestion, and by then the cat may be collapsing with blood in its chest. The single test that decides everything is prothrombin time (PT), taken at 48 to 72 hours, not at hour 2.
How the poison works
These compounds block vitamin K epoxide reductase, the enzyme that recycles vitamin K1 back into its active form. Without active vitamin K1, the liver cannot finish clotting factors II, VII, IX, and X. Factor VII has the shortest half-life at roughly 4 to 6 hours in a cat, so it falls first, and PT, which the extrinsic pathway drives, rises before any bleeding is visible.
That explains both the delay and the treatment. Nothing bleeds while the clotting factors already circulating are still adequate. Vitamin K1 given by mouth restores the enzyme, but the body has to build new factors, which takes 12 to 24 hours. Plasma or whole blood is what stops active bleeding, not vitamin K1, because vitamin K1 cannot fix factors that are not there yet.
Why 48 hours is the number that matters
Signs appear 48 to 72 hours after a toxic dose, and occasionally at 5 to 7 days with small repeated exposures. A cat with a normal PT at 12 hours has proven nothing, because factor VII has only just started to fall. A cat with a normal PT at 72 hours after a known single exposure is in a genuinely low-risk group, and that result is what allows a vet to stop worrying instead of starting a 30-day course on a guess.
Do not wait for bleeding to start the workup. The cats that die are usually the ones whose owners watched for a nosebleed for 2 days and arrived with a cat that was already pale and breathing hard. Book the PT before you see a single drop of blood.
| Bait type | Example active ingredient | Latency to bleeding | Vitamin K1 course | PT recheck |
|---|---|---|---|---|
| First generation | warfarin, chlorophacinone | 48 to 72 hours | 14 to 21 days | 48 to 72 hours after stopping |
| Second generation | bromadiolone, difenacoum | 48 to 96 hours | 21 to 30 days | 48 to 72 hours after stopping |
| Second generation, long acting | brodifacoum, difethialone | 48 to 96 hours | 30 to 45 days | 72 hours after stopping, then 2 weeks later |
| Unknown bait | unlabeled block or pellet | 48 to 96 hours | treat as long acting, 30 days | 72 hours after stopping |
The arithmetic of a single meal
Rodent bait is dilute. At 0.005 percent active ingredient, 20 g of bait contains 1 mg of anticoagulant. A 4 kg cat that eats 20 g of bait has taken a dose that often sits below the threshold for clinical bleeding in a single sitting, which is why many of these exposures end with 1 blood test and no treatment. The same arithmetic cuts the other way for repeated access: a bait station the cat can reach every night turns 20 g into 100 g in a week.
There is no reliable published toxic dose for cats by bait type, so the decision rests on 3 facts you can actually supply: the product name or the label, the estimated grams eaten, and the date. Photograph the box and the station before you clean anything up.
Secondary poisoning is real but small per meal
A cat that eats a mouse killed by anticoagulant takes in the residue held in the rodent's liver, and second-generation compounds persist there for months. One mouse is a small dose. The risk rises with the number of mice, and cats usually eat the head and chest first, where the residue concentrates.
Practical translation: a cat that brings in 1 mouse a month is not a case. A cat that eats 2 to 3 rodents a week during a baiting campaign should have a PT checked 48 to 72 hours after the last one, and the mice should be removed from the floor before the cat finds them.
What bleeding looks like in a cat
Pale gums and inner eyelids are the first sign most owners can see at home, followed by bruising on the ear pinna and belly, bleeding along the gumline, nosebleeds, and black tarry stool from blood in the gut. Blood in the urine, a swollen joint, weakness after a small jump, and sudden difficulty breathing from blood around the lungs are all later stages. A cat can bleed to death internally with no external blood at all, so gum color and breathing rate are the 2 things to check every 6 hours during the watch period.
Treatment and the rules around it
Vitamin K1 (phytonadione) 凭兽医处方 is the antidote, given by mouth with a fatty meal, usually split into 2 doses a day, for the full course in the table. Never shorten the course because the cat looks fine at day 10: factors are normal because the drug is working, and stopping early causes the second bleed. Vitamin K1 is not given as a rapid intravenous bolus because of anaphylactoid reactions, and it does not reverse active bleeding, which needs plasma or whole blood.
Do not make the cat vomit at home. Do not give aspirin, ibuprofen, or any NSAID for the bruising, all of which make bleeding worse. Do not let the cat jump from height or be handled roughly while PT is prolonged. Keep the cat indoors, because a bleeding cat that gets outside is a cat you cannot find in time.
Household rules if you must bait
- Use lockable bait stations only, and count the blocks: 4 in, 4 out, every week.
- Record the active ingredient and the date on the calendar, not just on the box.
- Keep the cat indoors for the full baiting campaign plus 2 weeks after the last block is removed.
- Sweep and dispose of dead rodents daily, with gloves, before the cat finds them.
- Never place bait in a shed, garage, or crawlspace the cat can enter.
- Tell the vet the product name at the first call; warfarin and brodifacoum need different courses by a factor of 2.
When to drive now
Drive now for any of these: pale gums, a nosebleed that lasts more than 5 minutes, black stool, bruising you did not see yesterday, labored breathing, or a cat that is weak 48 to 96 hours after bait contact. Also drive if a cat was seen eating bait and the product is brodifacoum or difethialone, because the course is long and starting vitamin K1 at hour 6 is far cheaper than treating a bleed at hour 72.
For other poisons where the first hours decide the outcome, read zinc coin ingestion and vitamin D exposure, and check the toxicity lookup tool for bait ingredients before you decide to wait.
Frequently asked
My cat ate rat bait 4 hours ago and seems fine. Can I wait?
You can wait to treat, but not to test. Bleeding starts 48 to 72 hours after ingestion because clotting factors must decay first, so a normal cat at hour 4 is expected. Record the product and grams eaten, then have PT checked at 48 to 72 hours. If the bait was brodifacoum, start vitamin K1 on the vet's instruction without waiting for a bleed.
Is my cat at risk from eating a poisoned mouse?
One mouse is a small dose, and most single meals do not cause bleeding in a cat. Risk climbs with repeated meals, 2 to 3 rodents a week during a baiting campaign, because second-generation compounds persist in rodent liver for months. Have PT checked 48 to 72 hours after the last rodent and remove dead mice promptly.
Why does the vet insist on a PT instead of just treating?
PT is the only test that shows the clotting cascade failing before blood appears, and it is what separates a 1-test exposure from a 30-day course. A normal PT at 72 hours after a known single exposure means low risk. Treating blindly for a month costs money and carries its own risk, so the test decides.