Pernicious Anaemia Society
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Subcutaneous B12 Injections - what size needle?

I am going to start going sub cut injections with Hydrox. I've done intramuscular injections twice - the second time I'm pretty sure I hit a nerve!!! I didn't inject, took the needle out and more blood came out than usual, then I re did the injection.

I just need to know what length needle to buy for subcut? I'm done a search but can't find an exact answer, some people say 1/2 inch, some say 1/8 inch!

I am an average sized female and will be doing this in my thigh.

thank you

5 Replies

Sorry about the bad experience. Upper outer quadrant is the location to avoid the nerves.

Of the several hundred times I've now injected IM over the past 4 years - I can recall only 2 or three times with an electric shock running down my leg. So I think it is rare.

Hitting a blood vessel happens more often and I find these come with more immediate pain and are followed by some blood.

I think these injections don't last as long either as I suspect the B12 leaks into the blood vessel.

Starting over was the right thing.

Subcutaneous - I think 1/2 inch needle. But I do only IM into gluteous Maximus so 1 inch and 1.5 inch work well for me.

Better luck next time.


I have recently begun SI subcutaneous and I use half inch insulin needles. It is so easy in fact I have more trouble drawing up than actually injecting. However I go into tummy fat below navel as my thighs are not very fatty. Push needle in at 45 degrees and inject slowly. Never had any problem with bruising or bleeding. Good luck whichever way you choose.

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If drawing up is a problem could you not draw up using a nice, thick, green needle - then swap to the orange? one.


I use 30g x 8mm for sub cut. It can be slightly tricky getting b12 out of the 1ml vials as the needle is very short.


If you are using single use glass ampoules you can turn the ampoule upside down after you have snapped the top off. The liquid will not leak out. You can then draw up the B12 without having to get the needle down into the ampoule.


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