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Lump three months after home B12 injection

post #1 of 8
Thread Starter 

Sometime around June, I gave my cat a B12 injection. She had been having stomach/digestion problems since at least January (clearly in pain after eating, intermittent diarrhea, avoiding food, barely moving...) and I wanted to make sure that an inability to absorb B12 in her irritated intestines wasn't preventing her from healing. Maybe it was a coincidence, but she seemed to get over her issues pretty quickly after that, and a couple weeks later she was knocking stuff off my desk and chasing it around and begging me for food when she finished eating. You know, normal healthy cat stuff.


This morning when I was petting her, I noticed a small lump between her shoulder blades, right about where I injected the B12. It's almost a centimeter long and skinny, maybe a millimeter or millimeter and a half at the thickest. I don't think it's infected, because she didn't seem to have any problem with me touching it. I didn't actually get a good look at it, though, because I could only find it when she was curled up on my stomach in bed and when I moved to find some light she wouldn't get in a position where I could see it. (It basically disappears between her shoulder blades in any position besides curled up in a ball.)


Has anyone else seen something like this from B12 injections? Should I be worried? I've heard of injection site cancers from vaccines, but not B12. I'm hoping it's just scar tissue because I wasn't very dexterous with the needle (I had to jab her twice), but now I'm wary about giving her any more.

post #2 of 8

Is she microchipped?  It's possible what you felt is actually her chip. 


I know it's possible for ANY injection to cause a sarcoma, but highly unlikely.  Vaccine related sarcomas are actually uncommon, but they are the most common of injection site sarcomas. I've never heard of any cats having any lump issues (especially after all time) from a B-12 injection, but I guess anything is possible.  Could you call you Vet and ask if there could be an issue.  And maybe next time you give it,  move over a little bit.  I guess you're giving it in her scruff area?  That's a big area, so you could move over to the side a bit, just in case the chip is close to the surface. 


We give our cat shots 3 times a week, probably using the same size needle you use for the B12 (insulin size) and so that we don't create scarring, we move all around her scruff area and come in from different angles.  She never even notices when she's getting the shots because she always gets them during a petting session :)

post #3 of 8
Thread Starter 

Ohhhhh maybe it IS the microchip! I didn't even think of that. Thanks for pointing out that (very likely) possibility. :)

post #4 of 8
I agree it's probably the microchip with the way you described it!
post #5 of 8

I read your question on the forum about giving b12 injections and wondered where you obtained the vitamin and syringes.

I am in the UK and have tried a couple of places, but I have been told unsuitable for a cat.

Please could you advise me as we have been taking our cat to the vet- 15 miles away- the cat is about 18 and of course does not like going, so if I could do them at home it would be ideal.

Best wishes to you and your kitty.
post #6 of 8
Thread Starter 

The B12 I got from an online pharmacy. But I could have most likely gotten it over the counter at a pharmacy here in Germany, it was just cheaper online. The needles are BD insulin syringes. Both are made for humans, I don't think they make special cat B-12. There is a difference between the kind that supposed to be injected and the kind you drip under your tongue, though, maybe they meant they only had the oral kind and it wasn't suitable for cats? Or whoever you talked to only studied human pharmacy and doesn't want to be liable for you killing your cat on their advice so is giving you the most conservative advice possible.


The kind for injection (it might be labeled for intramuscular injection, but you can use it subcutaneous, too) is sterile and doesn't have the irritating (or possibly cat poisonous) additives (flavorings, sweetener, possibly preservative) that sublingual drops would have.


Here's what I got:


When I run out, I'll get something different, though. The problem with this one is it's 2 ml and in a glass ampule that needs to be used all at once. I can reliably get about 0.7 ml into my cat before she starts squirming, so there's no way I'd get two syringes full in her in one sitting, and it wouldn't be sterile to leave out (plus it's inactivated pretty quickly if it sits out or is exposed to light). So next time I'd go for a more concentrated version, possibly a multi-dose vial if I can find it.


The ingredients in this example are:

Hydroxocobalamin acetate
    Active ingredient    1.044 mg equivalent to Hydroxocobalamin 1 mg
Acetic acid 99%
Sodium chloride



More commonly used are cyanocobalamin and methylcobalamin. Cyanocobalamin is generally cheapest and least active (but still effective!) because it has to be converted. Methylcobalamin and hydroxocobalamin are both already in biologically active form already. I think one of them stings a bit, maybe it was methylcobalamin? I couldn't find very much info on hydroxocobalamin in cats, but I think it was the most active form in humans.

post #7 of 8
Thread Starter 

Oops, got the syringe type wrong. It's Braun Omnican 40 (, but any insulin syringe would work. They have very thin needles and are made for small volumes. If you get a multi-dose vial, though, it might be easier to get syringes that don't have the needle already attached, because you'll want to change the needle between filling the syringe and injecting your cat. (Jabbing the rubber stopper on the vial will dull the syringe and make it harder to inject the cat.) The syringes I have are a real pain to remove the needle. Any needle size between 20 G and 30 G should be fine. (30 G is about as small as you can go, hurts less but takes longer to inject. I'm not sure if they measure needles by gauge or mm where you're at...)

post #8 of 8
Hello Samus and owner

Thank you for the information about vitamin B12 injections.

I am going to investigate your suggestions.

Happy New Year to you both.

J on behalf of Cadillac Tommy
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