What Happens If You Inject B12 Wrong?


Written by Elite HRT on May 27, 2022

Medically reviewed by

Camille Freking, Regulatory Affairs Specialist, MEDICAL ADVISOR

Vitamin B12 shots help to energize your body, support a healthy metabolism, and minimize fatigue. They’re invaluable for people living with anemia, and they work to help people with hormone imbalances reclaim their health and vitality. 

Getting B12 shots at a doctor’s office or wellness clinic can get expensive quickly. People often spend the same amount of money on a single shot as they would if they bought an entire multi-dose vial and gave themselves B12 injections at home, which is why many people do in fact turn to this latter option.

At-home vitamin B12 injections are cost-effective and safe. Most people who have a vitamin B12 deficiency find it very easy to give themselves B12 injections at home. 

Even though it’s simple to follow the instructions, there’s still room for user error. If you’re worried that you’ve injected your B12 wrong, here’s what you need to know.

Is It Safe To Inject B12 at Home?

The short answer: yes. 

If you have real vitamin B12 prescribed by a medical doctor, and the vial has been stored properly, it’s generally very safe to inject at home. 

When they prescribe an injectable form of vitamin B12, such as hydroxocobalamin or cyanocobalamin solution, your care provider will give you all the instructions you need for safe administration. Each syringe is intended to be used once and properly disposed of in a sharps disposal container. 

If you follow the instructions to the letter, you’re generally very safe. Most people find that vitamin B12 injections are easy and relatively painless. 

If you’re trying to avoid mistakes or you’re worried that you’ve already made one, you should call your healthcare professional for medical advice. 

How To Inject B12 at Home

This section is for informational purposes only. Again, if you’re having doubts about your ability to self-administer your B12, contact your care provider for additional guidance. 

First and Foremost, Only Use Legitimate Vitamin B12 Supplements

Legitimate and safe vitamin B12 needs to be manufactured in a facility that adheres to FDA standards. It also needs to be prescribed by a doctor. You can’t buy it online without talking to a doctor, and you should never order it from outside the country.

There are lots of shady websites that make it seem easy to get vitamin B12 injections. However, you can rarely trust what they’re selling you. You’ll have no way of knowing whether or not the product is contaminated or expired. You won’t even have a way to be sure that the vial actually contains vitamin B12. 

If your vial of vitamin B12 wasn’t prescribed by a doctor and dispensed by a legitimate pharmacy, dispose of it. Don’t risk injecting an unknown substance. 

Preparing To Inject Vitamin B12

The first step should always be thoroughly washing your hands with warm water and antibacterial soap. Some people feel safer when they wear medical-grade gloves before giving themselves injections. Even if you do wear gloves, you should wash and dry your hands before putting the gloves on. 

Next, follow these steps to finish prepping:

  • Sterilize the injection area by wiping it thoroughly with an alcohol prep pad. 
  • Remove the cap from your single-use syringe, and pull back on the plunger to fill the syringe with air up to the measurement line of your B12 dosage (i.e. if your dose is 1 CC of 1000 mcg B12 solution, fill the syringe with air up to the 1 CC line). 
  • Flip the vial upside down, and stick the needle-end of the syringe into the top of the vial.
  • Push the air into the vial — this will help prevent a suction effect when you draw the actual solution out. 
  • Adjust the needle so it’s sitting in solution, and pull the plunger back to draw up the amount of vitamin B12 your doctor recommends.
  • Remove the syringe from the vial, and recap the vial. 
  • Ensure the syringe is pointed up toward the ceiling, and slowly press the plunger down to push all excess air out of the syringe, including any air bubbles you see in the solution. 

Giving Yourself a Vitamin B12 Injection

Vitamin B12 injections are intended to go into a muscle (aka they are intramuscular shots). For most people, the easiest spot to access is the muscle at the top of the thigh or the side of the hip. 

Some people also find that using their dominant hand to inject their non-dominant bicep works perfectly fine. For example, if you’re right-handed, you can inject your vitamin B12 into your left bicep. 

However, the bicep or upper arm is generally not recommended since a slight miscalculation can cause significant shoulder pain. 

  • Push the needle straight down into the injection site. You’ll feel the needle as a pinching sensation as it pushes past the skin, but it should only feel mildly uncomfortable. If you feel a shooting or radiating pain, gently but immediately pull the needle straight out.  
  • Slowly push the plunger down on the syringe until the entire injection has been administered. 
  • Pull the needle straight out. 
  • Place the cap back on the needle and dispose of the entire syringe in a sharps container

Important Note: You should never just throw needles into the garbage, as they’re considered biomedical waste. When your sharps container gets full, your local health department will take it. Some pharmacies also have take-back programs for sharps containers. 

What Happens If You Inject B12 Wrong?

Most people don’t have a hard time injecting vitamin B12. If you inject B12 wrong, here’s what you can expect and how to handle common problems. 

You Won’t Experience the Benefits

Vitamin B12 can be injected intramuscularly (into the muscle) or subcutaneously (into the fatty layer of tissue under the skin). Intramuscular injections are absorbed more quickly since muscles have more blood vessels and better circulation, which generally means your body can use the B12 faster and more efficiently.

If you miss the muscle and inject the B12 into the subcutaneous fat, nothing bad will necessarily happen. Your injection should still work, but the benefits and effects will likely be less noticeable. If that’s what you did, you usually have no reason to worry. If you find the thought bothering you, you can always call your prescribing provider for guidance. 

Soreness at the Injection Site

If you inject at an angle or too aggressively, the injection site may remain sore for a few days. This is generally normal, and it usually heals on its own. Over-the-counter pain relievers like ibuprofen or acetaminophen can make the discomfort a little more manageable. 

Remember, you should always inject at a perfect 90-degree angle. You want the needle to go straight down into the muscle. You should also push the plunger down slowly, rather than attempting to inject all of the vitamin B12 in one fast pass. 

In the meantime, avoid injecting again near the sore site. Switching arms or legs may also help. Give the area some time to heal. If you can’t reach another injection site, have someone else help you. 

Most importantly, remember that injections can cause a pinching sensation or mild residual muscle soreness, but they should never cause stabbing, radiating, or sharp pain — if this is the case, contact your prescribing provider immediately for additional guidance. 

Abscesses Under the Skin

An abscess is a buildup of blood, pus, and bodily fluid that occurs as a result of a bacterial infection. Abscesses are extremely rare but can occur when injections are administered improperly.

Abscesses often begin as sore red spots that may be warm to the touch. They quickly grow in size and become more tender. Eventually, abscesses rupture and leak fluids. 

Reusing needles, using contaminated vitamin B12, injecting with dirty hands, or injecting into an improperly prepared site can cause abscesses to form under the skin

Abscesses are serious, and the longer they go untreated, the more serious they’ll become. If you suspect an abcess, make sure to seek medical care right away.

What To Do If You Injected B12 Wrong

If you aren’t experiencing any side effects and there are no signs of an abscess, you generally don’t need to do anything. You might want to speak with your doctor for further help or instructions for administering the injection properly. 

If you believe you’re developing an abscess or if you currently have an abscess, seek immediate medical attention. Your doctor needs to treat the area and drain the abscess. You’ll likely be prescribed antibiotics to help your body fight off the infection. The area may also require special medical dressings that need to be changed according to your doctor’s instructions.

Using Vitamin B12 Injections Safely

The Elite HRT team is composed of experienced hormone therapy and nutraceutical wellness doctors. We’ll work with you to medically evaluate your candidacy for vitamin B12 injections. If applicable, we’ll write you a prescription for vitamin B12 for you to fill through your pharmacy of choice to help increase your level of B12.

We’ll also give you instructions for safe injection to guide you through the process from start to finish. 

If you ever have any questions or concerns, our team is always here for you. Contact us to get started


How To Give Yourself Intramuscular (IM) Injections | UW Health

Abscess | MedlinePlus

Best Way To Get Rid of Used Needles and Other Sharps | FDA