Vitamin K for Cats: Overview, Dosage & Side Effects

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Vitamin K1 (phytonadione) is most commonly used to treat cats who have eaten rat poison.

Vitamin K is a fat-soluble vitamin needed to produce factors involved in bone mineralization and normal blood clotting. If your cat does not have enough vitamin K, there can be a delay in their blood clotting. This causes a risk of spontaneous and uncontrolled bleeding.

Vitamin K for Cats Overview

Medication Type:

Vitamin

Form:

Injectable, tablets, capsules, compounded liquid

Prescription Required?:

Yes

FDA Approved?:

Yes

Brand Names:

No licensed veterinary preparations. Human preparations may have a trade name such as Konakion® or Mephyton®. Or it may just be called Vitamin K1 or Phytomenadione.

Common Names:

Vitamin K1, Phytomenadione

Available Dosages:

Injectable 10mg/ml, tablets/capsules vary

Expiration Range:

Tablets typically have a shelf life of 1-2 years when stored properly. Injectable solutions may have shorter shelf lives after opening. Always check product labeling for details.

Many mouse and rat poisons work by inducing a vitamin K deficiency, resulting in fatal internal bleeding. If your cat ingests rat poison, your veterinarian will treat them with vitamin K to counteract the poison’s effects. Luckily, if started quickly, this can be very effective.

Cats can also become vitamin K deficient if they have problems with their liver, gallbladder, or fat absorption.

Read on for everything you need to know about vitamin K and cats, including when it is prescribed, how to administer it, and what to look out for if your cat is taking it.

About Vitamin K for Cats

Vitamin K is used as an antidote for cats who have accidentally ingested mouse or rat poison.
Image Credit: Viacheslav Lopatin / Shutterstock.com

Vitamin K is an essential vitamin, meaning it isn’t made in the body and your cat must eat enough in their diet to stay healthy. If your cat eats a nutritionally complete, balanced diet, they will receive enough vitamin K. So, it isn’t something you need to supplement in a normal cat.

Because of its important role in blood clotting, cats who are deficient in vitamin K can suffer from serious bleeding disorders. The most common cause of vitamin K deficiency in cats is rodenticide poisoning, which occurs if your cat eats poison designed to kill rodents such as rats and mice. Many types of rodenticide poisons are ‘anticoagulant’ – they work by causing severe vitamin K deficiencies in the rodent, leading to fatal internal bleeding. Cats who ingest the poison are affected in the same way and can suffer from life-threatening spontaneous bleeding.

Less commonly, vitamin K deficiency can be caused by certain liver conditions, gall bladder obstructions, fat absorption problems, and chronic antibiotic use.

Vitamin K deficiency is treated by administering vitamin K medication. This replaces the lost vitamin K, allowing your cat’s blood to clot normally. It usually begins to work within 24-48 hours.

Special Precautions for Cats Receiving Vitamin K

Your cat will have been prescribed vitamin K medication because they have low levels in their body. This means they are at risk of bruising and spontaneous bleeding, so it is important to handle them gently.

Cats should be kept quiet and calm while they are receiving treatment. You should try to prevent your cat from jumping or strenuous playing, to reduce the risk of injury. This might mean confining them to one quiet area of the house for the first week or so. They should be kept inside until they are fully recovered.

Dosing Information for Cats

Note: This information does not replace a vet visit. While these are the most common dosages, you should consult with your cat’s veterinarian on the exact dose and treatment protocol

Injectable Vitamin K

Vitamin K therapy will usually start with a course of injections before being continued with tablets at home for several weeks. H_Ko / Shutterstock.com

In an emergency, such as ingestion of anticoagulant rodenticides, your veterinarian would administer vitamin K as an injection under your cat’s skin as this works faster than oral medication. The dose range is 0.25 – 2.5 mg per kg body weight.

If your cat has signs of bleeding, your veterinarian may begin with a high-dose injection. This will be followed by a lower dose every 12 hours until active bleeding has stopped. At this point, your cat will be moved onto oral vitamin K medication – usually within 1-3 days.

Oral Vitamin K

There are no licensed veterinary products containing vitamin K for cats. So, it is common to use human medications instead. This is called ‘off label’ use and must only be done under the direction of your veterinarian.

Oral vitamin K is available in tablets, capsules, and compounded liquids. It is usually given twice a day, about 12 hours apart. Your veterinarian may recommend a tapering dose – one that starts higher and is gradually reduced – to wean your cat off gently. While dosing is individual to each case, it is likely to be in the range of 0.25 – 2.5 mg per kg of body weight.

Oral vitamin K is usually continued for several weeks. Your cat may need blood tests to check the medication is working and their blood is clotting normally before stopping.

How to Administer Vitamin K to Cats

Your cat will need oral vitamin K medication for several weeks until their blood is clotting normally. Dora Zett / Shutterstock.com

Vitamin K is best absorbed when given with food, especially fatty food. You may be able to hide a tablet or capsule in a strong-flavored tasty treat. If your cat has been prescribed a liquid, you may be able to mix it into a wet food. Check with your veterinarian which food to use, as some cats may need to avoid high-fat food (for instance, if at risk of pancreatitis).

If your cat will not eat a tablet you may need to administer it directly into the back of their mouth. See this guide for How To Give Your Cat a Pill. Be sure to give them a fatty meal or treat after their medication to ensure it is absorbed effectively.

Side Effects of Vitamin K for Cats

Vitamin K tablets are usually well tolerated by cats and side effects are uncommon. However, contact your vet immediately if you notice anything unusual.

There can be side effects from vitamin K injections, including:

• Pain, swelling, or bleeding at the injection site
• Allergic reaction or anaphylaxis (very rare)

Note: vitamin K should be injected under the skin (subcutaneously) and not into the vein (intravenously) due to the risk of anaphylaxis, or into the muscle (intramuscular) due to the risk of hematoma.

Overdose and Emergencies

An overdose of vitamin K in cats can destroy their red blood cells. High doses can also cause bleeding disorders, despite being given to prevent it. So, if you are worried your cat may have taken too many vitamin K tablets you should contact your veterinarian for advice immediately.

Potential Drug Interactions of Vitamin K for Cats

Several medications may interact with vitamin K, and so should be used with caution:

• Thyroid medication
• Aspirin
• Chloramphenicol, metronidazole, or erythyromycin (antibiotics)
• Allopurinol (used to treat leishmania or bladder stones)
• Diazoxide (used to manage blood glucose levels)
• Itraconazole (antifungal)
• Cimetidine (used to treat or prevent stomach ulcers)
• Propranolol (used to treat heart conditions and high blood pressure)
• Warfarin-type drugs

All types of medication have the potential to interact, even non-prescription drugs. So, be sure to tell your veterinarian about anything you are giving your cat, even if you don’t think it’s important. This includes herbal remedies, supplements, vitamins, or over-the-counter treatments.

Mineral oils such as liquid paraffin may reduce vitamin K absorption from your cat’s gut. So, you should stop using this while your cat is treated with vitamin K to ensure it can work effectively.

How to Store Vitamin K

Vitamin K tablets should be kept at room temperature in a light-resistant container with the lid shut. Compounded medications should be stored according to the label.

As always, keep any medication out of reach and sight of children and pets.