Giving Your Cat a Vitamin B12 Boost.

Giving your cat a B12 shot is a really inexpensive way to make a sick cat feel better quickly.  If your cat won’t eat no matter what tempting concoction you put in front of it, B12 may get your cat on course again.

Traditional Siamese cat sitting on white porch swing.

My sweet, perfect little traditional Siamese cat Cleo.

If you take your cat to the vet because they’re generally feeling blah, they’ll often give your cat a quick Vitamin B12 shot to help them feel better.   For cats with chronic diseases B12 for cats is something you can do at home once a week to stimulate their appetite.

But yes, a needle is involved.  And yes, you have to stick it in your cat.

Suck it up. They’re your cat and you love them.  True, if the roles were reversed your cat wouldn’t do the same for you but that’s only because they don’t have fingers.  Or a job to help pay for things like medicine.

B12 is also known by the name Cobalamin so don’t get confused if you see that term thrown around online.

My cat Cleo (who I had to put down after a lengthy illness with advanced renal disease) felt much better after I gave her a B12 shot and even though I knew it wasn’t curing her it made me feel better to know that I was at least making her feel better.  

The moment she was diagnosed with advanced renal disease I started to give her Subcutaneous fluids which helped with the effects of the disease immensely.  If you have a cat that has renal disease go now and read my post on how to give your cat Subcutaneous fluids.  I also gave her an anti-nauseant once a day because part of renal disease means your cat constantly feels nauseous.

That all worked fine for over a year.  And then one day out of the blue this cat would not eat.  She not only went off food, she seemed to develop an aversion to it. Just the sight of her food dish would make her start to gag. 

She could only stomach one thing.  Bacon.  So I started cooking up pounds of it and sitting on the floor with my cat, both of us scarfing down the bacon. As one does with their cat.

If your cat is at the point where it will NOT eat, try to find one thing they can stomach. It might be cat treats, bacon, tuna, cheese … whatever it is, it’s your one and only shot at getting calories into them until you can get to the vet. 

Just getting something into them is sometimes enough to trigger their appetite.

After a couple of bouts of her not eating regular food I called my vet and said I thought it was time to start giving her some B12.  We had discussed it a few visits prior.

A half an hour and $12 later I was at home giving Cleo her B12 shot.  Within 2 days she was not only eating again, she was eating more than she had eaten in the past year.   Plus, I was left with a fridge full of bacon I had to eat before it went bad, so that was a little bonus for me and a big bonus for my back fat.

The reason cats with chronic disease benefit from B12 is because their disease is preventing them from absorbing B12.

Symptoms of a B12 Deficiency in Cats

  • lethargy
  • vomitting
  • off food / weight loss
  • confused
  • trouble walking or jumping

Does Your Cat Need B12 shots?

Cats with these conditions or diseases are prone to being low on Vitamin B12 or (in the case of heart disease) needing extra.

  • Diabetes
  • IBD
  • Pancreatitis
  • Sick or unwell cats who won’t eat
  • Renal Disease
  • Hyperthyroidism
  • Heart Disease
  • (if your cat is drinking a lot for any reason it can lead to B12 deficiency)


Adequate B12 is important for a cat’s …

  • Appetite
  • Brain Health
  • Gastrointestinal system
  • Nerve system

What does B12 do for your sick cat?

For sick cats the most important thing B12 does is give them their appetite back and just generally make them feel better.  Like medical marijuana but for cats.  And not marijuana.

B12 is water soluble vitamin so there’s no worry of overdosing them with B12.  If your cat has too much B12 in them, they just pee it out.

Cat Not Eating?

  • Cats have a VERY strong instinct to eat even if they aren’t feeling well. So if they get to the point that they aren’t eating for a day or two it’s important to make an appointment with your vet right away.
  • In the meantime try to find something, ANYTHING that your cat will eat. For my cat it was bacon. Nothing else.
  • Not eating, even for a short period of time (24-36 hours) is dangerous for a cat and can lead to liver damage.
  • Sometimes a whole bowl of food is overwhelming for them, try to offer just a tiny bit of food to tempt them. 
  • Try EVERY kind of wet cat food you can find. Different brands, flavours etc. Don’t worry if it’s the cheap stuff and you only feed them the good stuff. You just need to get calories in them even if it’s in the form of Friskies. When my cat wouldn’t eat I went to the pet store and bought one can of just about everything and offered a bit from each one once every hour until she found one that didn’t repulse her.
  • Do NOT try to force your cat to eat, which is likely to create even more of an aversion to food.
  • Sometimes the smell of food will turn your cat off, but if you put a tiny bit on their lip to lick off, their appetite gets stimulated and they’ll eat.

If you’ve tried everything take your vet to the cat and also ask them about B12

How to Give Your Cat a B12 Shot

Don’t give your cat a B12 shot without consulting your vet first.


1. Get your B12 and appropriate needles from your vet.  They’ll tell you the proper dosage which corresponds with your cat’s weight. This tiny little $12 bottle will last for months.

Hands holding a vial of vitamin B12 and syringe.


2. Peel back the paper on the syringe package and remove the needle. Everything is all together, you don’t need to do anything other than remove it from its packaging. The needle is teeny, tiny.  So small that most cats won’t even feel it going in.

Opening small syringe package.


3. Turn the bottle of B12 upside down, insert the clean needle into the rubber seal and withdraw the required dosage.

Withdrawing red B12 from vial.


4. Make a tent out of the skin at your cat’s scruff.  You want to inject right in that tent so the needle will be going into an air pocket between the skin and the muscle.  Just into air really.

Cat's neck scruff being pulled upwards to create a tent of skin at her neck.


5. Pierce the skin with the needle and inject the B12 into the cat.

Injecting Siamese cat with B12 at her scruff.

Giving Your Cat a Vitamin B12 Boost.

Giving Your Cat a Vitamin B12 Boost.

A step by step guide to giving your cat a B12 injection.

A $12 bottle will provide enough B12 for many injections.


  • B12
  • Injection needle*


  1. Get your B12 and appropriate needles from your vet.  They’ll tell you the proper dosage which corresponds with your cat’s weight. This tiny little $12 bottle will last for months.
  2. Peel back the paper on the syringe package and remove the needle. Everything is all together, you don’t need to do anything other than remove it from its packaging. The needle is teeny, tiny.  So small that most cats won’t even feel it going in.
  3. Turn the bottle of B12 upside down, insert the clean needle into the rubber seal and withdraw the required dosage.
  4. Make a tent out of the skin at your cat’s scruff.  You want to inject right in that tent so the needle will be going into an air pocket between the skin and the muscle.  Just into air really.
  5. Pierce the skin with the needle and inject the B12 into the cat.


Remember to inject into the air pocket between the skin and the muscle.

Be careful with the needle, it's very sharp and you can easily accidentally puncture yourself.

*the appropriate size of needle will be given to you by your vet

Need a video?  Here you go.  

If you have a cat, they are very good at hiding any symptoms of feeling unwell so if you aren’t sure if your cat is sick read this post on the signs of how to identify a sick cat and do what you can for them. You can always count on them to make you feel better.  So they should always be able to count on you for the same.


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Giving Your Cat a Vitamin B12 Boost.


  1. Santagesha says:

    Anyone whose cat received this shot at the vet, did your cat violently throw up? Like projectile vomit??? I have to call the doctor back tomorrow morning because it was bad and out of nowhere. I’m so nervous for my fur baby. I just want him okay :(

  2. Leslie says:

    When I was a kid in the 1960s, we usually adopted dogs from the Humane Society (this was when it was not ‘cool’ to announce to total strangers that your dog was a ‘rescue.’ It was decidedly uncool to have a ‘mutt.’)
    I have had many mixed breeds over the years plus a few dogs that I bought from breeders. Because I wanted a dog whose history and providence I knew. When my kids were young, I usually had Labradors because I trusted them around kids.
    Sharing your life with a pet is a big responsibility and often a decade or two commitment. I do not think people should apologize when they buy a breed of animal that they really have thought long and hard about and want, considering this is a life commitment.
    I also thinking adopting strays, rehomed animals, etc. is good. Although I’m sick to death of people bragging about it, as if shopping and paying a lot of money from a ‘rescue’ operation makes them a savior.
    In general, do-gooders shouldn’t brag about it.

    • Dusty Cat says:

      Leslie, it isn’t bragging as the meaning most of us are familiar with.

      It is ‘saying out loud’ that they love animals enough to take an actual STEP to save their lives AND to let the world know that ‘perhaps’ they should ‘consider’ saving animals too.

      And, no, it is not a statement against those who want a specific kind of pet – and those who would feel any kind of ‘apologetic guilt’ would have their own internal reasons.

      Live and let live…

    • Stevie says:

      Whoa, where did your comment even come from? Not making much sense.

  3. R. Wise says:

    My vet suggested this for my cat today. Your article highlights several of the key points my vet made. Additionally, if you have a cat that won’t eat anything try baby food. They tend to go for the smelly stuff so Ham, Turkey or Chicken. I hope the tip will help someone.

  4. Laura says:

    Brilliant post!!! This our second bout of starvation …1st just before Christmas, literally spent a whole week hand feeding and praying for our 11 year olds appetite to come back. Yes took her to vets no temperature but they couldnt hold her to take bloods, took her home and next day she was eating again…PHEW…but then 4 weeks later here we are again…vet gave her a b12 shot and shes right as rain scoffing like no tomorrow even asking for 2nds and 3rds…relief…vets suggested a urine test instead of putting through sedation so hoping we find out just what’s going on as vet has no idea has her heart and all her internals feel fine to the feel…..shes a sphynx so within 3 days of not eating the effects are quite visual. Thanks for the post, I can now kind of see where we are going now. And will definately ask vet possibility of renal disease.

  5. board says:

    Unlike vitamin B complex, injectable vitamin B12 (which is a pinky red colour) does not sting, so some people give this to their cats during or immediately after sub-Qs.

  6. Laura Bart says:

    Thank you for your post and for showing all the comments – great info. I just gave my 9-year old cat her B12 shot (my first time, her second) and she reacted very positively almost immediately. My imagination? I had a witness so I don’t think so. Maybe it was the Temptations treats she got as a reward. I’m hopeful. She has issues keeping her number-twos in the litter box, possibly due to an old injury to her colon. We added a second litter box, started the B12 and she gets probiotics daily with a new canned food (Royal Canin Selected Protein) Progress! 😻

  7. Darwin.cone says:

    Does b12Have to be refrigerated?

    • Cathy says:

      We just started giving our cat B12 injections. She has small cell lymphoma in her Jejunum and IBD in her duodenum. The vets office told us the liquid does not need to be refrigerated, but it is very sensitive to and can be degraded by light. Keep it wrapped up or in something to protect it from light exposure.

  8. Diane Berwick says:

    My vet recommended B12 shots monthly after my cat had a very serious attack of pancreatitis at which time I thought my cat was going to die. She has done so well on the B12 — so far, no more pancreatitis.

  9. Gigi Sittmann says:

    Thank you for this page. My niece in the States sent me the link after I told her that my cat had been diagnosed with CKD and I had lost all hope of being able to help her when she stopped eating. I live in Ontario so links in the US often contain information on products not available here so I am doubly grateful that I found you and your common sense approach.

    • Karen says:

      Hi Gigi! Good luck with your little kitty. I also gave her subcutaneous fluids every other day for over a year and that helped immensely. Best of al the B12 is really cheap! ~ karen

  10. Kathy says:

    Can I give my cat a B12 pill & if so how much?

    • Judy says:

      B12 isn’t adsorbed properly in the GI tract by cats who need supplementation, so it has to be given by injection, just like in humans with pernicious anemia.

  11. Paula Clark says:

    We lost our cat, Bob, to renal disease last November. We fought the loss of appetite for four years with changes in food, giving him anything he could or would eat, fluids and B12 shots. He just finally said that’s enough. He was 13 and the best cat ever. We are dog rescuers and he loved checking out all the foster dogs like he was the boss of the house. We miss him greatly. He was found in our back yard as a barely alive tiny kitten and we had not intentions of keeping him. But we did and we loved him.

  12. Pam'a says:

    Just please, please don’t keep any creature alive if it’s suffering. They weren’t meant to languish, and as hard as it is, good pet parents know when to let them go, and that it’s an act of love… I firmly believe we’ll see them again.

  13. Jody says:

    You’re such a good soul…

  14. Stefanie Barrett says:

    I can’t thank you enough for this post! My 4 year old siamese looking cat was recently diagnosed with diabetes. Even though we have regulated his glucose, he still seems sluggish and uninterested in even his treats. We visit the vet weekly and I will certainly ask about B12.

    Thanks again!

    Stefanie in Memphis

  15. judy says:

    Mandy-thanks for the info-sadly the minute I say he weighs 175 lbs and is not trusting of people except for my son,his owner, the vet office suggests we try another vet. I am going to inquire of the vets I found through Karen’s suggestion of vets who specialize with dogs that are fearful. thanks again-it’s so nice when people reach out to help one anoth

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  17. judy says:

    Thanks Karen for the info re: our Rottie,I will follow up with local Vet recommendation

  18. Sue says:

    I’ve been through the administering sub-cutaneous fluid route before but, like another reader, B-12 was never mentioned by the vet. Good to know. Thank you. My mother gave herself B-12 injections for the last 5+ years of her life–doctor authorized–and they really helped her with her energy level.

  19. Bev Bennett says:

    My elderly cat has been getting B12 shots for quite a few months now after discovering he had kidney issues and was not feeling well. I am not as brave as Karen to do it myself so I go to the vets and the charge is not expensive Jack is feeling so much better since getting his shot I want one myself
    See you at the vets Karen
    Jack & Bev

  20. linda says:

    Wonderful information! My elderly cat could use anything to make her feel healthier…. But she’s just old. I will definitely check into getting B12 for her. I took it my self when dieting as part of the program- gave myself the shots once a week. EZ peasy!

  21. judy says:

    could you describe how to get a blood sample from a dog. I am so worried about our 175 lb Rottweiler having heartworms. He seems lethargic,pants and just does not seem well to me. He is only 4 years old but he is overweight- no vet will see him because of abuse when he was young he is very leery of people. He reared around with our vet when he tried to examine his ear and the vet had to put a muzzle on him. He won’t see him again. I am afraid to just give him heartworm meds because if he does have them the medicine will cause him harm?

    • Leslie says:

      Judy, drawing blood from pets is tricky for professionals sometimes, it’s probably not something you want to DIY – it could be dangerous for you and damage your dog’s trust in you. There are also specialized containers for blood collection and accurate heartworm tests are generally not available over the counter. A vet should be able to give you some medicines to help with your boy’s anxiety before vet visits (I also have a dog who gets anxious about the vet). Another idea would be to find a certified Fear Free veterinarian. This training goes beyond the basics of animal handling and means that the vets and technicians who are certified are working hard to make veterinary visits as pleasant as possible for your pet. Here’s a link to the directory:

    • Manda says:

      It is admirable that you want to help you pet and thank you, but please get them to a vet ASAP. It could be a host of other things (potentially serious) and a blog is not necessarily the best place to diagnose your pet. As mentioned, Karen had already taken her pet to the vet for a diagnosis. I can speak from experience on having to have your dog muzzled. Mine has to be as well for any vet visit–nails, bloodwork, shots etc. as well as being given anxiety medicine before the appointment. It’s for the dog’s safety and the staff. If that particular vet won’t see your dog again, you can try another vet. There is a big difference between an aggressive dog and one that is only fear aggressive based on situation. I wish you luck at your next vet appointment!

  22. Kiara says:

    For diabetic cats, B12 reverses diabetic neuropathy. My cat was walking really funny (on his hocks) and that was one reason I brought him to the vet. Cats are sneaky – they hide illness really well.

    Anyway, I gave him the oral B12 which I got online from a human pharmacy (I bought a special sugar and sugar alcohol free version safe for diabetic cats – Americans can purchase Zobaline but I had to get a human diabetic version) and that, combined with insulin, got him walking normally in just days.

    Now he’s doing great and barely even needs insulin anymore, but I’m wondering if the old silver fox wouldn’t benefit from a B12 injection every few weeks for good health.

  23. Kate says:

    Thank you for sharing this! I’m sure this is our near future. One of our cats has kidney disease AND is diabetic. I was totally freaked out when the vet said i was going to have to inject insulin twice a day!!! But for some reason (thankfully), it hasn’t been too bad. He does most those things you’ve listed but he still eats, for now. I think I should eat bacon with him anyway, just to cover all our bases! :)

  24. Shawna says:

    Wonderful news for all those suffering senior cats (and people)! All these years with all my cats and I’ve never tried this – amazing! Of course, I’ve never sat on the floor eating bacon with my cats either, so there you have it! Always something to learn. :)

  25. Gillian Thompson says:

    Dear Karen,

    Thank you for sharing this video!! I have 5, count ’em 5 cats, 2 of which are seniors, so I know at least one of them will have to have this done at some point. I had no idea about the B12 shots, not even from a Vet. This gives us all hope for all of them. Thank you thank you thank you!!!
    Maybe I should give myself a B12 shot, LOL

    • Karen says:

      “Maybe I should give myself a B12 shot, LOL” … When the vet told me everything the B12 shot could do I said the same thing myself, lol. ~ karen!

    • Tracey DeCredico says:

      I get B12 shots every 4 to 6 weeks at my Primary care. Keeps me running on all cylinders. If I miss, I know.
      Give it a “shit” you won’t B sorry😂

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