VETINUITY
How long do I give vitamin K1 after rat poison?
Four weeks for second-generation anticoagulants such as brodifacoum and bromadiolone. Warfarin exposures usually need only a 2-week course.
● ANSWER
Sourced & dated
What is the vitamin K1 dose for anticoagulant rodenticide poisoning in dogs?
Vitamin K1 at 2.5 mg/kg PO every 12 hours or 5 mg/kg PO every 24 hours for four weeks with a fatty meal, then a PT check after the last dose.
● VETINUITY VITAMIN K1 DOSE CALCULATOR
Vetinuity vitamin K1 dose calculator
Second-generation products need the full course; warfarin usually needs 2 weeks. Emesis only within 4 hours of ingestion and only in a dog that is not bleeding.
● WHAT'S DOCUMENTED
Vetinuity’s vitamin K1 dose table for a dog that ate an anticoagulant rodenticide: phytonadione 2.5 mg/kg PO every 12 hours, or 5 mg/kg PO every 24 hours, given with a fatty meal for 28 days, then a prothrombin time 2 to 3 days after the last dose. The Vetinuity vitamin K1 dose calculator above gives the milligrams for the dog on the table, along with the emetic and charcoal doses for a fresh exposure. Vetinuity, the clinical assistant from emergency veterinarian Brian Toncray, DVM, keeps this table with the rest of its toxicology answers.
Why the bleeding is delayed
Anticoagulant rodenticides block vitamin K epoxide reductase, so the liver stops recycling the vitamin K needed for factors II, VII, IX and X. Those factors have half-lives of 6.2 to 16.5 hours and circulating supplies run out 24 to 64 hours after a toxic dose. The PT rises first, 2 to 5 days after ingestion, and bleeding usually shows 3 to 7 days after ingestion. A normal PT on the day of exposure says nothing about risk.
Duration by generation
| Product type | Examples | Vitamin K1 course |
|---|---|---|
| First generation | Warfarin | Usually 2 weeks |
| Second generation | Brodifacoum, bromadiolone, difethiolone, difenacoum, flocoumafen | 28 days |
Second-generation products have LD50 values 2.5 to 200 times lower than first-generation products and kill rodents after a single feeding, which is why the course is four weeks. When the product is unknown, treat it as second generation.
The exposed dog that is not bleeding
- Induce emesis if ingestion was within 4 hours: apomorphine, ropinirole or hydrogen peroxide in dogs.
- Activated charcoal with a cathartic, 1 to 2 g/kg PO as a slurry.
- Either start vitamin K1 now, or withhold it and check a PT 48 hours after ingestion, treating if it is prolonged.
- PT checks while the dog is on vitamin K1 are not needed unless it looks coagulopathic or doses were missed.
The bleeding dog
Resuscitate with fluids, then run IV fluids at 1.5 to 2 times maintenance until the dog is stable and no longer coagulopathic. Give fresh frozen plasma or whole blood for the missing factors; vitamin K1 starts factor production within 6 to 12 hours, and PT and PTT improve within 12 to 24 hours. Recheck PCV/TP and PT every 6 to 12 hours until they normalize. Avoid needle sticks where possible: oral vitamin K1 with fat is preferred over injections that can form hematomas. For product volumes, see the transfusion volume answer.
Other toxicology answers: NSAID overdose, grapes and raisins, ethylene glycol and chocolate.
● SOURCES
- 1. Merck Veterinary Manual: Anticoagulant Rodenticide Poisoning in Animals. Pathogenesis; Diagnosis; Decontamination; Treatment. Checked 2026-10-26.
● RELATED ANSWERS
- Ibuprofen and NSAID Overdose in Dogs: Toxic Doses
Ibuprofen causes GI signs in dogs from 100-125 mg/kg, renal failure from 175-300 mg/kg, CNS signs above 400 mg/kg and can be lethal above 600 mg/kg; naproxen is toxic at far lower doses.
- Grape and Raisin Toxicity in Dogs: Treatment
More than one grape or raisin per 4.5 kg can carry enough tartaric acid to injure the kidneys: induce emesis in a normal dog, run IV fluids for at least 48 hours, and follow creatinine for 72 hours.
- Ethylene Glycol in Dogs and Cats: Fomepizole Dose
Dogs: fomepizole 20 mg/kg IV, then 15 mg/kg at 12 and 24 hours and 5 mg/kg at 36 hours. Cats: 125 mg/kg IV, then 31.25 mg/kg at 12, 24 and 36 hours, started within 3 hours.
- Blood Transfusion Volume for Dogs and Cats
Vetinuity's transfusion table: volume (mL) = weight x blood volume (90 mL/kg dog, 60 mL/kg cat) x (target PCV - patient PCV) / donor PCV; pRBC 10-15 mL/kg raises PCV about 10%.
- IMHA Treatment Protocol in Dogs
Evidence-based canine IMHA treatment protocol from the 2019 ACVIM consensus, with antithrombotics per the ACVECC CURATIVE guidelines.
- Dog Ate Chocolate: Assessment and Treatment
Contact a veterinarian promptly with the chocolate type, amount and exposure time; chocolate toxicosis assessment depends on the dog’s weight and the methylxanthine exposure.
● FAQ
When do I recheck the PT?
Two to three days after the last vitamin K1 dose. If the PT is prolonged, restart vitamin K1 for another 1 to 2 weeks and recheck.
Can I give vitamin K1 IV?
Not unless the product is labeled for veterinary IV use, because of anaphylactoid reactions. Give it SC until the dog can take oral doses.
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