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. Richard G Martin says:

    My cat is very thin because he don’t like most foods. He use to eat some dry cat food but threw up a lot. I tried all types and flavor foods, nothing worked. I finally found that he liked Gerber baby food, chicken or beef. Baby food is expensive so I stated making my own by taking cooked chicken and running through blender until it looks like soup. If any has unblended chicken or beef he will not eat it. My vet can’t find any reason for him not eating. Some cats can’t tolerate corn in the food. Hope some of this will help

    • Pat says:

      Has your cat had a VDI panel which test for inflammatory bow disease vs lymphoma. I would consider it. I regret a previous vet not offering it to me. All other bloodwork for my cat were normal. If he had offered this I would have started treating the cat with a different diet. Damage has been done for us. Good luck.

  2. Cynthia DaCosta says:

    How often can I give b12 shots? I gave one yesterday and it helped immensely. Can I give another today?

    • Jeannie says:

      I’m starting my cat on b12 injections today 🥳, and his prescription is for one shot per week! So daily sounds like too much, but ask your vet. For oral b12, daily is normally okay ✨✨

  3. I. Herz says:

    Good article. I have an eighteen year old Maine Coon that’s been diabetic for about six years. He gets two insulin injections every day, one every twelve hours when he eats. For the most part this is usually fine, but bodies fluctuate and there have been times when the dosage would change to either less or more. In the last three months he’s had two very scary hypoglycemic episodes where his glucose was as low as 53. I almost lost him twice, but was able to get him back to normal. These episodes are really tough on him and take several days to fully recuperate from. I’ve since adjusted the dosage of insulin from 3 units down to 2 units. So far so good, however, he started walking on his hocks a year ago, known as nueropothy. He can get around, but not for long distances. The cat eats perfectly well, but his water intake has crept up since the dosage change.

    This is what interested me about your article. I have known about B12 methylcobalamin for quite some time. According to research that I’ve read, the methyl B12 actually reverses the nerve damage caused by high glucose in the blood over a period of time. The problem is that I was not able to find an injectable version of Methyl B12 on the market. You mention that it could be found for $12. What I had to finally do was to find a compounding pharmacy, have my vet write the prescription and concentration – then have it made to spec. I got two 20ml bottles for $100, which is very expensive. The dosages are pretty large too at 2.5 ml.

    My goal is to try and improve my cat’s walking ability so he can have a more normal spoiled life. :-)

    My question is this: Is it necessary to have the methylcobalamin in the B12 to repair the nerve damage or will regular B12 do the same thing?

    Where is subcutaneous (injectable) B12 available?

  4. Annette says:

    Great article! My soon-to-be 16 yr old tabby has advanced renal disease and so I have her on a special diet (which she likes) and vitamin B12 shots (which she doesn’t– though it makes her feel so much better). At first, she took the shots with grace but now she gets annoyed with her every-two-weeks injection. She doesn’t react to it going in, but then if it takes longer than two seconds she fights it and just wants outta here! So I’ll be looking for a vet that does it for cheap, and if I’m stuck with doing it I’ll try practicing giving an injection to a tomato :) (just in case my technique isn’t up to par). She vacuums up treats like there’s no tomorrow, so keeping her focused on food is an issue, LOL. Any suggestions are appreciated!

  5. Jennie says:


    Your video and post are so encouraging. I knew I had to give my cat Samson a B12 shot and was terrified that I would hurt him because he doesn’t have a light of skin between his shoulders. After reading your post and watching your video, I lost my fear and realized to your point that I need to suck it up because this will make my cat feel better and they can’t do this themselves. Thank you for giving me the courage!

  6. My cat is 20 years old. She has had ups and downs for the last two or three years. She always comes back but this time she’s not eating well and has lost down to five pounds. The vet gave her a B12 last Friday and she began eating a little better bet back to square one. She still walks through the house jumps up and down off the bed but I know she feels bad. She doesn’t sleep with me anymore and stays in a spare bedroom . I don’t want her to suffer but how to determine when euthanizing is the last resort? I don’t want to give up on her but don’t want her to suffer either. Thanks so much for your help

  7. Patricia Marino says:

    My granddaughters 6 year old cat has started peeing on bedding etc., Vet said he has crystals in urine other than that couldn’t find any other reason. Said it is behavioral. Any ideas for helping?

    • Lin N says:

      My ginger boy did that. Ultimately it was because, he didn’t like the litter In the litter box or sometimes it was he was mad at me. (We have a close relationship 😅) He will now use the litter box after I tried a few different types. He likes Arm&Hammer Light. He also is an indoor/outdoor cat. He goes out in the morning and in the evening and does his thing.

    • Linda says:

      cranberry powder in her food. That worked wonders for my cat and dog. get her off
      of all dry food. you can try her on frozen raw food, duck by Raw Dynamic is what I’ve been using. Good luck

      • joy says:

        De-mannose is a white powder made from cranberries (cranberry juice isn’t good for an animal.) 1/4 teaspoon in a tablespoon of filtered water will cure any bladder infection in a few days. I put it in a shot glass & use a small feeding syringe in the side of her mouth. People can use it also .It works great. Dry food is not recommended for cats. (no matter what any vet says) I even read a report that feeding dry food can cause
        diabetes. A raw diet is best.

  8. Tina says:

    I have a kitten who has some health problems but the don’t affect his prodigious appetite. But you commented on bacon. I put a large griddle out to cook 2 pounds of bacon, got it sizzling and went to take a quick shower. When I returned, Bob, the Apprentice Kitten had hooked a nail into each of the pieces of bacon and pulled them off. One piece of bacon he hung over the edge of the stove, as a treat for the dogs. The rest of the bacon (half cooked) was piled on the counter for the cats. I’ve learned my lesson.

  9. Penny says:

    Karen I had no idea!! I had a diabetic cat for 3& 1/2 yrs and in between giving him 2 shots a day, it never occurred to me that this might help! Sad. I was taking those shots for myself for like 3 yrs. Now that I know….I’ll be helping my elderly pets!

  10. 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 :(

  11. 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.

  12. 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.

  13. 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.

    • Jodi Cantler says:

      Mira tax transdermal cream in alternating ears is what was prescribed by my vet. It is an appetite stimulant and anti nausea medicine. It has worked wonders for my cat who also lost his appetite and about 3 pounds of weight due to IBD.

  14. 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.

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