Comprehensive Vet Guide 2025: Vitamin K1 (Phytonadione) for Dogs & Cats 🐾💉

Written by Dr Duncan Houston, BVSc – trusted veterinarian & Ask A Vet founder 👨‍⚕️🐾

Vitamin K1 (phytonadione) is a fat‑soluble vitamin crucial for creating clotting factors (II, VII, IX, X) in the liver. In 2025, it remains the first‑line antidote for rodenticide poisoning and is vital in treating bleeding from liver disease, bile obstruction, or antibiotic‑induced deficiency. This guide covers how it works, dosing, safety, monitoring, and how Ask A Vet, Woopf & Purrz assist in managing pet bleeding emergencies. 🩺📘

1. Mechanism & Importance

Vitamin K1 enables the liver to activate clotting factors II, VII, IX, and X, essential for normal blood clotting. Without it, pets may bleed uncontrollably :contentReference[oaicite:2]{index=2}.

It is the only effective antidote for anticoagulant rodenticides (e.g., warfarin, brodifacoum) and treats bleeding related to liver dysfunction or malabsorption :contentReference[oaicite:3]{index=3}.

2. Forms & Administration Routes

• Oral tablets/chewables: best absorbed when given with fat—cream, oil, or fatty food :contentReference[oaicite:4]{index=4}.
• Injectable (SC/IM/IV): used in emergencies for rapid effect; SC or IM preferred—IV risks allergic / anaphylactic reactions :contentReference[oaicite:5]{index=5}.

3. Indications & Urgency

• Rodenticide poisoning: critical—bleeding usually starts 2–5 days after ingestion :contentReference[oaicite:6]{index=6}.
• Liver or biliary issues: support when clotting factor production is compromised :contentReference[oaicite:7]{index=7}.
• Antibiotic-induced deficiency: especially after prolonged oral antibiotics :contentReference[oaicite:8]{index=8}.

4. Dosing Guidelines

Rodenticide toxicity:
Emergency injectable start: 2.2 mg/kg SC once, then 1.1 mg/kg SC every 12 hours until bleeding stops, transitioning to oral :contentReference[oaicite:9]{index=9}.
Typical oral: 2.5–6 mg/kg once daily; up to 3 weeks guided by prothrombin time/PIVKA‑II trends :contentReference[oaicite:10]{index=10}.

Oral forms take 6–12 hours to work; injectable works in 24–48 hours :contentReference[oaicite:11]{index=11}.

5. Onset & Treatment Duration

• Injectable: Clotting resumes within 24 hours :contentReference[oaicite:12]{index=12}.
• Oral: Effects begin after 6–12 hours, though full normalization may take days :contentReference[oaicite:13]{index=13}.
• Therapy typically lasts 2–6 weeks depending on rodenticide half‑life and lab results :contentReference[oaicite:14]{index=14}.

6. Side Effects & Risks

• Injection-related: pain, swelling, bleeding; risk of allergic/anaphylaxis if IV or IM :contentReference[oaicite:15]{index=15}.
• Oral administration: well tolerated; rare allergic reactions :contentReference[oaicite:16]{index=16}.
• Overdose risk: In cats can cause red blood cell destruction and anemia—use accurate dosing :contentReference[oaicite:17]{index=17}.

7. Contraindications & Cautions

• Known allergy to phytonadione—use only if benefits outweigh risks :contentReference[oaicite:18]{index=18}.
• Avoid IM/IV routes due to risk of severe anaphylaxis—use SC if necessary :contentReference[oaicite:19]{index=19}.
• Use cautiously during pregnancy/lactation—limited safety data :contentReference[oaicite:20]{index=20}.

8. Drug Interactions

• Oral antibiotics, cimetidine, chloramphenicol, metronidazole, erythromycin: may reduce Vitamin K absorption or metabolism :contentReference[oaicite:21]{index=21}.
• Mineral oil: interferes with uptake—avoid during therapy :contentReference[oaicite:22]{index=22}.
• Warfarin-type drugs: Vitamin K reverses their effects—inform human vets if shared environment :contentReference[oaicite:23]{index=23}.

9. Monitoring & Follow-Up

• Track bleeding symptoms—nosebleed, bruising, blood in urine/stool.
• Lab checks: prothrombin time or PIVKA‑II before stopping oral therapy :contentReference[oaicite:24]{index=24}.
• For rodenticide cases, continue treatment for full expected duration of toxin presence in body.

10. Storage & Handling

• Oral tablets/chewables: room temperature, sealed, away from children/pets :contentReference[oaicite:25]{index=25}.
• Injectables: store per label, protect from light and shake before use.
• Wear gloves; avoid accidental ingestion—especially chewables :contentReference[oaicite:26]{index=26}.
• Safely dispose of used syringes and leftover pills.

11. Role of Ask A Vet, Woopf & Purrz

• Ask A Vet: Emergency dosing guidance, lab interpretation, overdose triage.
• Woopf: Dosing and lab-testing reminders, bleeding symptom logs.
• Purrz: Track pet energy, appetite, bruising, bleeding—share insights with your vet.

12. Pet Owner Experiences

Many families report visible signs of recovery—cessation of bleeding and energy return—within 48 hrs of injectable dose. Chewable tablets are often described as “treat-like” and stress-free to administer :contentReference[oaicite:27]{index=27}.

13. FAQs

🐾 Missed dose—what do I do?

Give as soon as remembered unless it's near the next dose; do not double up—call your vet if unsure :contentReference[oaicite:28]{index=28}.

🐾 Can Vitamin K1 be used long-term?

Only when underlying causes persist (e.g., liver disease or malabsorption). Monitor labs and adjust, stopping once clotting normalizes.

🐾 My pet is bleeding again after treatment—should I restart?

Return to your vet immediately—repeat labs may be needed and oral therapy restarted.

🐾 Can I give with or without food?

Best absorbed with a fatty meal—especially oral forms :contentReference[oaicite:29]{index=29}.

14. Summary Table

15. Final Thoughts from Dr Duncan

Vitamin K1 remains an essential, lifesaving therapy in 2025 for clotting crises—from rat poison to liver disease. When given promptly, monitored properly, and supported by tools like Ask A Vet, Woopf & Purrz, most pets stabilize and recover fully. Always consult your vet for tailored dosing and follow-up care. 💗🐾

For emergency guidance, lab support, or medication reminders, visit AskAVet.com and download the Ask A Vet app. Your pet’s safety matters—every moment. 🐶📱🐱