Does the Vitamin B-12 Shot Have Side Effects?

by Dr. Edward Group DC, NP, DACBN, DCBCN, DABFM Published on

A bottle of b-12. While the b-12 shot addresses B-12 deficiency, it may also be prescribed to boost energy and much more.

Vitamin B-12 is to the human body what gasoline is to a car; without it, you’re not getting anywhere. A diet that includes meat, fish, and dairy products can provide natural sources of B-12; however, these foods typically carry a heavy toxic load. Vegetarians and vegans can suffer from B-12 deficiency, so can meat eaters, making B-12 deficiency a common problem many people solve with supplementation or a B-12 injection.

For those who don’t care for a shot, dietary supplementation like VeganSafe™ B-12, with the two active forms of B-12, methylcobalamin and adenosylcobalamin, may be as effective as a B-12 shot.

What is a Vitamin B-12 Shot?

The shot delivers a high dose of therapeutic B-12, usually in the form of cyanocobalamin or hydroxocobalamin. For those who don’t care for a shot, oral supplementation with the two active forms of B-12, methylcobalamin and adenosylcobalamin, may be as effective as a B-12 shot. [1]

Those who cannot digest or absorb B-12 as a result of inherited genetics or damage to the stomach and small intestine require more than can be absorbed from sublingual supplementation. In situations where a high dose is needed, or where injection is the only option, the B-12 shot is used. In some cases, B-12 shots are used as an energy booster, since B-12 plays a critical role in cellular energy production.

Reasons for a B-12 Shot

Vitamin B-12 deficiency symptoms include depression and mood disorders, fatigue, memory failure, anemia, low blood pressure, and high homocysteine levels. While the shot addresses B-12 deficiency, it may also be prescribed to boost energy, as a therapy for depression, or to drive cognitive function. Researchers are also exploring its potential as a therapy for bipolar disorders, shaky leg syndrome, and autism.

Getting the B-12 Shot

Before getting the shot, make sure to inform your doctor of any allergies, nutritional supplements you may be taking, or if you’ve recently consumed large amounts of alcohol. At the appointment, the doctor or healthcare professional delivers the shot directly into muscle, usually into the thigh or upper arm, for easy absorption into the bloodstream.

B-12 Shot Side Effects

The dosage amount and the type of B-12 used appears to have some control over side effects. As a note, the common side effects of excess vitamin intake include flushing, diarrhea, nausea, and vomiting. Here are the side effects you might experience from the two common B-12 shots:


This form of B-12 is the one we find in our food. When delivered as a B-12 shot, mild side effects may include soreness at the injection site, itching, diarrhea, and swelling. Serious side effects include muscle cramping, weakness, or an irregular heartbeat. Although rare, some very serious side effects are chest pain, shortness of breath, slurred speech, sudden vision changes, and weakness on one side of the body. You should always contact your doctor immediately if you experience any of these reactions.


This is the synthetic version of vitamin B-12 used in supplements and in the B-12 shot. Mild side effects of diarrhea and swelling can occur. Serious side effects include muscle weakness, extreme thirst, confusion, shortness of breath, headache, exhaustion, reddening of the skin, and a fast or irregular heartbeat. Very serious side effects such as chest pain and difficulty breathing are rare. You should always contact your doctor immediately if you experience any of these reactions.

Contact your doctor immediately if you experience any symptoms of allergic reaction such as itching, swelling, severe dizziness, rash, or difficulty breathing after receiving a B-12 shot. The best way to protect against side effects is communication. Make sure your doctor knows all the medications and drugs (including alcohol) you may have taken prior to getting the shot. Information on your family’s medical history also helps.

Do you get B-12 shots? What has your experience been? Let us know!

Watch an In-Depth Video on
Everything You Need to Know About Vitamin B-12
References (1)
  1. Thakkar K1, Billa G2. Treatment of vitamin B12 deficiency-Methylcobalamine? Cyancobalamine? Hydroxocobalamin?-clearing the confusion. Eur J Clin Nutr. 2014 Aug 13. doi: 10.1038/ejcn.2014.165.

†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. Global Healing Center does not dispense medical advice, prescribe, or diagnose illness. The views and nutritional advice expressed by Global Healing Center are not intended to be a substitute for conventional medical service. If you have a severe medical condition or health concern, see your physician.

  • I’m getting two shots a month, I would like to start having one a week. I just wonder if that is to much? When I have the shot its the only time I feel normal or like my self,

  • What does your doctor think?

  • gene

    this formula of B-12 by dr group is the shiznitz, meaning very, very good.

  • Kongingh12

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  • Tersia

    Same with me how many can you get in a month??

  • Jaime Jensen

    What about reactions to b12. Allergies.

  • Mols

    I have experienced the symptoms of B12 deficiency after I received my B12 shot. Shaky Keg, Confusion, Sensation in My Leg. B12 level was 167. My Dr told me it could not be from the shot and it is probably psychosomatic because the B12 level was not very low in the begining. When I had it, it worked like 4 sleeping pills. Was such reaction normal? Can I take Oral supplement while I receive a B12 shot per month?

  • Jan

    Are side effects such as shortness of breath more likely to occur just the day of the injection, or anytime between shots?

  • Brendan Devitt

    167 serum b-12 level is very low. I was 219 pg/ml and could barely walk or function in Jan 2016. After finding Facebook support group for Pernicious Anemia/B-12 Deficiency, I received two injections from my doctor. I started self-injecting hydroxocobalamin 1 mg daily in early March. Today is day 71 and I have life back. For me, after about 4 injections, my b-12 deficiency symptoms got worse for about a week. This is thought to be because the body is waking back up and nerve damage is starting to repair, along with increased red blood cell production which caused me strong bone pain. Check out the FB support group and you’ll find hundreds of stories much like mine. I also take 5600 mcg methyl folate sublingual daily (critical to methylate the hydroxocobalamin, which enables our body to take it up into cellular level), vit D-3, magnesium, and potassium-rich foods. Best wishes for feeling better soon!

  • Lorri Nowell

    I do have Hashimotos I am taking synthroid 50 micro daily. Extremely tired so had a b12 test results were 256 Dr.put me on cyanocobalamin 1000mcg 4 weeks then once monthly. After watching video am I taking something useless?

  • mouse

    I had a B12 injection last evening. I didn’t sleep well and have a headache this morning. I rarely have headaches so I’m concerned.

  • sam

    Do you have mercury fillings in your mouth?
    Vitamin B12 is very VERY toxic when you have mercury burden in your body. I found out the hard way

  • Christina Scott

    I want to know why the b12 shots and pills cause me within hours to be extremely fatigued like I can’t hold my eyes open tired. I see where there are others that have experienced this but there’s no clear answer as to why this happens! I recently was diagnosed with Ehlers-Danios syndrome and kerataconos and also scoliosis and back degeneration all started early on and I can’t help but think that the link to all of them is a protein problem and a genetic defect of not being able to produce proteins.

  • Julie

    Judy, im wondering what ever happened with your story (your post is from 2 years ago), however, I started b-12 injections weekly for 6 weeks then went tomonthly for a while & because my levels werent increasing, we went back to weekly. Been on injections 14 months! I started having trouble with my legs in February and it was diagnosed from everything from akathesia to restless less syndrome to spondyloarthritis. From February till mid July, it progressed so fast, I could hardly walk at all. I would fall. Lose balance, I was in such pain, I coukdnt eat or keep anything down, ive lost 40 lbs in 8 months & I was pretty small to start. My hair was falling out because I was deficient in EVERYTHING! My sister & a friend found that it “could be” the form of B-12 injection (cyano…). Your body has to convert that kind into another form to be absorbed & clearly MY body cant (#’s havent budged after a yr of injections & daily supplements!). Found a spray that u spray under your tongue, hiold in mouth for 2 min or so (tasty). Itd B12 Organic Spray. Vegan Methylcobalamin. Everything is organic: beet, brocoli, carrit, kale, every vegetable, every fruit, etc. Compared to the corrosive hydrochloric acid, alluminum, Sodium Chloride, Benzyl Alcohol, Sodium hydroxide & hydrochloric Acid for preservatives. Cyanocobalamin appears as dark red crystals or as an amorphous or crystalline red powder. After doing my own research, I found that all of my symptoms ARE side effects. I am an educated consumer, I know it may not mean 100% that it was the injection. I also must say im not a wholistic, all natural, type of person, I always popped a pill for anything. But last week I thought I was going to be wheel chair bound at 35. I needed assistance walking. I started taking turmeric for inflammation (thinking it was the arthritis), and 2 days ago started this B12 spray and I am 95% better. Im sorry this is long but if I could help just one person… I had never been more scared in my entire life, thinking I’d be a paralyzed single mom with a 5 year old. Hope this helps. I know I wont ever just pop whatever pill my doctor tells me ever again. If anyone has any similar experiences, PLEASE let me know. I hope im on the right track & it wasnt just a flare up that has passed for the meantime. Thanks!

  • AP

    I’ve been taking the shots for a couple weeks now and really like the effects. I feel the energy and alertness. Placebo? Maybe. None the less I’m a proponent.

  • Charmaine Taaffe

    im sitting here with the tears rolling down my cheeks, last year i was on my 3 monthly injections but then nov last year i took so weak i felt i was going die, i thought it was a bad flu i didnt relate it to my shots, but then i decided right try another way off taking this my body started to get a little better, i had started to walk a little better, but last wk I thought I maybe need to try this injection again as i felt so tired again, worst idea ive ever had 1 wk on and im back to square one the pain ripping through me then feeling dizzy and sick, now its like every muslce in my back is in spasms, then tonite i feel like my legs are a ton weight and im finding it hard to walk again, Ive cried buckets today cause i feel so stupid for getting this injection again, I feel like ive just jumped back till last year again 🙁

  • Cynthia

    The above stories are very interesting. Sorry though for your complications and pain. My mother has had two B-12 injections and she too seems to be having effects from the 2nd one more than the 1st one. Her arm where the injection was put in has been sore for over 2 months now and the whole arm now is getting very painful, plus she is having bad back pain as well. I was wondering, Julie, could you share the company and name of the B-12 organic spray on here, please. And how quickly did the turmeric start working for you? What dosage did you take? Thanks.

  • d Brad

    I bought vitamin b12 at a Mexican pharmacy they actually call it Tribedoce, they have a version that contains lidocaine it somehow lidocaine helps at the time of injection, it feels less of a “burn” with it. Anyway, I been having this injection Because I suffer from horrible stabbing back pain is hard to continue doing whatever is that I’m doing constantly, because is so painful but I got my life back recently because of these b12 injections. I get so happy that I run! Is amazing to wake up with no pain. My pain is due to a herniated spinal disc on L5 it hurts really bad I Been taking muscle relaxers which make me so incredibly sleepy living with pain is no life if I have to give myself an injection every other day for the rest of my life in exchange to actually be able to walk for over 20 minutes or to dance so be it. I apply lidocaine lotion on the injection site (my butt cheeks) it aids with the pain of the needle since is not such a small needle. I know the medicine is working because instead of excruciating pain I get like a nice tingling sensation throughout my legs and buttocks, I gave myself a shot (yes, I self inject) every other day, got 10 shots I was supposed to take another set of ten injections 3 months later but the pain came back at a week later so I’m doing them again. Like I said I will take an injection any day over having no life! I’m turning 30 years old and I have felt like I’m 120 years old. Depressing really. I hope this helps someone. Last year I started with an oral solution which I break off the glass dark vile pour it on a cup, add little water to get all of the vitamin out and that did the trick for me past year, I have tried it again but I didn’t succeed so I went with the injection because I couldn’t take this anymore. I have bought this b12 at the Mexican border, a pharmacy called “farmacias similares” don’t know if other Mexican farmacies carry this I know they have discounts on mondays so I stock up on their medicine whenever I can. I don’t work for this farmacies or anything like that at all. I just don’t want back surgery and I found this solution. By the way I found a box of the oral viles is called quimtetril I paid about 100 pesos for 10 viles which is like 5 dollars and is taken every other day, I have felt great with these viles that there was no pain and so I stopped taking them but the pain came back and when I retook them they were probably expired, I bought them again but I had more results with the injections. Good luck if you suffer from back pain this has given my life back I will try to exercise more and more because strong back is also beneficial. oh the injections as cheap too. 60 pesos for 5 injection with lidocaine. (Besides I apply lidocaine lidocaine lotion 20 minutes B before my shot) 60 Mexican pesos is like 3-4 dollars.

  • Dawn Buchanan

    I also suffer headaches with B12 injection. I have had to stop taking then. If you do not have a deficiency then taking the shot could be a little much

  • linda

    I have Hashimotos too plus pernicious anaemia with test result of 190. After taking vit b12 injections once a month for 6years i now have b12 results of 627. I have so much more energy and feel so much more brighter and alert mentally. You are def not taking some thing useless I now take shots ever three weeks and will do for life. I havnt watched the video.

  • artrat

    Rice Bran and Bee Pollen.

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