Anticoagulant rat bait does not make a cat bleed on the day it eats it. The latency is 3 to 5 days, sometimes 7, because the poison works by blocking vitamin K recycling and the clotting factors it starves out have their own half-lives. That gap is why an owner sees a normal cat on day 1 and a pale cat on day 5. Any known exposure means a call to the vet or a poison service the same day, not a wait for symptoms.
Why nothing shows up for 3 to 5 days
Second-generation anticoagulants such as brodifacoum, bromadiolone, difenacoum, and difethialone inhibit vitamin K1 epoxide reductase. Without recycled vitamin K, the liver cannot finish factors II, VII, IX, and X. Factor VII has the shortest half-life at roughly 4 to 6 hours, so the prothrombin time starts to drift within 24 to 48 hours, but the cat does not bleed until factor levels fall far enough to break the clot, which lands at day 3 to 5. Brodifacoum also has a tissue half-life measured in weeks, so a single meal can keep the liver blocked far longer than the bait was on the floor.
PT at 2 times normal is the line that matters
Prothrombin time (PT) is the test to ask for. A PT prolonged beyond 2 times the upper normal limit, roughly 24 to 30 seconds against a 12 to 15 second reference, supports anticoagulant exposure and is the value most vets treat on. Timing matters more than the number: test at 48 hours after the last known exposure, repeat at 72 to 96 hours, and treat if either draw crosses 2 times. A normal PT at 48 hours is good news, not a discharge — one more test at 96 hours catches the slow cases.
Three steps for secondary poisoning
A cat that eats a poisoned mouse is a secondary poisoning case, and the math is not obvious because the dose depends on the mouse. Step 1: pin down the product. Read the bait station label for the active ingredient and its concentration, usually 0.0025 to 0.005 percent for second-generation anticoagulants. Step 2: pin down the meal. A cat that ate a whole fresh carcass, gut included, took in far more than one that mouthed a dried tail; gut contents carry the highest load. Step 3: set the monitoring plan from steps 1 and 2, with a PT at 48 and 96 hours, activity restriction, and prescription vitamin K1 if the PT crosses the line.
Compare the four common bait types
| Bait type | Typical label strength | Signs appear | Key test | Vitamin K1 helps |
|---|---|---|---|---|
| Anticoagulant, 2nd generation | 0.0025 to 0.005 percent | 3 to 5 days | PT over 2 times normal | Yes, by prescription |
| Cholecalciferol (vitamin D3) | 0.075 percent | 12 to 36 hours | Calcium and phosphorus | No |
| Bromethalin | 0.01 percent | 2 to 24 hours | Neurologic exam | No |
| Zinc phosphide | 1 to 2 percent | 1 to 12 hours | Vomit, breath, blood gas | No |
What bleeding looks like at home
Watch for bruises on the belly and inner thighs, blood on the gums after a chew toy, nosebleeds that stop and restart, black tarry stool, red urine, pale gums, fast breathing at rest, a limp from bleeding into a joint, and a cat that sleeps more than usual. Weight the check to the 3 to 5 day window. A cat that is fine on day 2 can be in trouble on day 4, so a daily 60 second gum-and-skin check for 7 days costs nothing and catches the turn early.
Confine for 2 weeks
Restrict the cat to one room or a large cage for 14 days after a confirmed exposure. Two reasons: any knock, jump, or scuffle during a low platelet window turns into a bleed, and confinement keeps the cat away from the bait station and from hunting the mice that are still dying. Keep food and water within 1 meter, a litter box within 2 meters, and no cat trees for the 2 weeks. Bleeding cats should not be carried around or given injections unless the vet has the PT in hand.
Autumn bait season, by the numbers
Mice move indoors when the night temperature holds below 10 degrees C for 3 nights running, which in most temperate zones lands in the last 2 weeks of October. Peak activity sits in the 2 hours after dusk and again 2 hours before dawn. Bait stations belong against walls every 8 to 10 meters, and pellet or block baits go soft and unpalatable above 70 percent relative humidity, so a damp garage floor is where bait gets ignored and mice keep coming. Check stations every 48 hours and log what was taken.
Make the house boring to mice instead
Snap traps inside tamper-resistant boxes, no poison, remove the problem. Seal gaps over 6 mm, since a mouse passes a 6 mm hole, store dry food in bins with gasket lids, and clear spilled birdseed within 24 hours. If bait is unavoidable, use a locked station and count blocks in and out weekly. Dried leaves, mold, and standing water in gutters matter too; the autumn leaf and plant hazards piece covers the plant side, and the toxicity lookup tool screens a product name in under a minute.
Five steps after a suspected exposure
- Photograph the bait label and note the hour the cat was last seen near the station.
- Call the vet or poison control the same day; do not wait for a bruise to appear.
- Do not induce vomiting and do not give any human vitamin product at home.
- Book PT at 48 and 96 hours, and confine the cat for 14 days.
- Vitamin K1 (phytonadione) only by veterinary prescription, with the course length set by repeat PT.
Terms mentioned in this article
Frequently asked
My cat ate a mouse that may have been poisoned. What now?
Call the vet or a poison service today and note the hour. Read the bait station label for the active ingredient and strength, then say whether the cat ate the whole carcass or just part of it, since gut contents carry the highest load. A PT test at 48 hours and again at 96 hours decides whether treatment starts, and the cat stays confined for 14 days.
How long after exposure should the PT test be done?
At 48 hours after the last known exposure and again at 72 to 96 hours. Factor VII falls first, so an earlier test can look normal while the clotting cascade is still draining. A single normal PT at 48 hours is not a discharge; the second draw at 96 hours is what catches slow metabolizers and the long tissue half-life of brodifacoum.
Can I give vitamin K1 at home?
No. Vitamin K1 (phytonadione) is a prescription product, and the dose and course length depend on body weight, the specific bait, and repeat PT values. Giving it without a PT result can hide a progressing bleed and delay the test that would have shown it. Keep the cat confined, skip human vitamin products, and let the vet set the plan.