How to give a b12 injection

Updated November 21, 2016

Vitamin B12, a large molecule stored in muscle and other organs, is obtained primarily by eating animal and dairy products, although our bodies make a small amount of it in the gastrointestinal tract. To absorb B12, we need a "helper molecule" (technically, a glycoprotein dubbed "intrinsic factor," secreted by the stomach lining). While some people have a gene that prevents them from making this intrinsic factor, others lose that ability as they age. This lack of B12 absorption results in pernicious anaemia. There are two main ways to get B12 absorbed into our systems--through an intranasal spray and by intramuscular injection. While the idea of giving someone (or yourself) an injection may seem frightening at first, it is not difficult.

Wash your hands thoroughly. Unwrap the syringe if it is sealed in plastic. Set it (with needle cover on the needle), the B12 vial, a cotton ball and the container of alcohol on the counter.

Wet the cotton ball with alcohol and wipe the rubber top of the B12 vial well. Pick up the syringe, remove the needle cover and pull back on the plunger to allow an amount of air in that is equivalent to the amount of B12 you will be injecting.

Hold the syringe in your dominant hand, being careful not to allow the needle to touch anything. Hold the B12 vial in your non-dominant hand, and push the needle into the rubber top. Inject the air from the syringe into the B12 vial while the vial is still upright.

Invert the B12 vial with the needle inside the fluid. Pull back on the plunger and watch the marks on the syringe to see the amount of B12 that you have transferred to the syringe. Stop when you get to the appropriate amount. Tap the side of the syringe to force any bubbles up and out of the syringe and into the vial. Withdraw the needle from the vial and put the vial on the counter. Recap your needle (only recap clean, unused needles) and set the syringe aside. Be sure to triple check your dosage before giving it.

After locating the appropriate intramuscular injection site using appropriate landmarks, use a second cotton ball wet with alcohol to cleanse the skin. Pull the skin taunt where it was cleaned. With your dominant hand holding the needle, aim the needle at the cleansed area and with a quick motion like you are throwing a dart, plunge the needle into the muscle.

There are specific areas in which to give intramuscular injections such as B-12. Be sure to discuss thourghly with your health care provider where to give your injection and how to find the site accurately. Giving the injection in the wrong site can lead to complications with absorption. You may also be more likely to hit bone, nerves and blood vessels if you are not in the correct site.

Pull back slightly on the plunger and look to see if you pull any blood back into the syringe. If all is clear, push down on the plunger until all the B12 has been transferred from the syringe to the muscle. It is important that there is no blood aspirated into the syringe--if there is discontinue the injection and begin again. If blood is aspirated into the syringe, it is likely you are in a blood vessel and will be giving the medication via intravenous method rather than intramuscularly which will change the absorption rate.

Pull the needle out of the muscle quickly and immediately apply the cotton ball with the alcohol on it. Have the individual press down hard on the cotton ball for a minute or two. Apply a bandage to the injection site.


This is an intramuscular injection, so the needle must go deep into the muscle, as opposed to a subcutaneous injection, such as an allergy shot, that goes just below the skin. If you must give yourself a B12 injection, it is easier to do it in the upper thigh muscle, slightly toward the outside. Be sure to clarify the exact muscle site with your heatlh care provider before injecting.


If you see blood when you pull back on the plunger, you have probably hit a vein or artery. Withdraw the needle and begin again with a new needle, new dosage of medication and a new site. For your own safety, have a professional nurse or doctor instruct you on the proper method of giving a B12 injection and have her watch you do it the first time. If you give an injection in the buttock, make sure it is high and on the outside of the buttock, as the sciatic nerve runs down the centre of the buttock, and you do not want to injure that main nerve.

Things You'll Need

  • B12 vial
  • Syringe
  • Alcohol
  • Cotton balls
  • Band-aid
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