Dangers of vitamin B12 deficiency

Vitamin B12 deficiency can occur in all kinds of individuals. It may be of particular concern if you are following a vegan or vegetarian diet, or taking medications that reduce your absorption ability of vitamins. This video looks at what exactly a vitamin B12 deficiency can lead to and the ways in which you can obtain vitamin B12 through your diet or by taking B12 supplements.

This video was created by Demystifying Medicine students Dhruvika Joshi, Prabhjot Khabra, Minahil Jabeen and Vanessa Lombardo.

Copyright McMaster University 2017


1. Bruins Slot, W., Merkus, F. W., Deventer, S. J. H. V., & Tytgat, G. N. (1997). Normalization of plasma vitamin B12 concentration by intranasal hydroxocobalamin in vitamin B12-deficient patients. Gastroenterology, 113, 430-433.

2. Daily Intake. (2017). Canadian Food Inspection Agency. Retrieved 30 October 2017, from http://www.inspection.gc.ca.libaccess.lib.mcmaster.ca/food/labelling/food-labelling-for-industry/nutrition-labelling/information-within-the-nutrition-facts-table/eng/1389198568400/1389198597278?chap=6

3. Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B b6 s, folate, vitamin B b12 s, pantothenic acid, biotin, and choline. (1998) (pp. 306-356). Washington, D.C.

4. Ermens, A., Vlasveld, L., & Lindemans, J. (2003). Significance of elevated cobalamin (vitamin B12) levels in blood. Clinical Biochemistry,36(8), 585-590. doi:10.1016/j.clinbiochem.2003.08.004

5. Ganeson, S., Thanawala, N., & Hussain, N. (2013). Vitamin B12 deficiency: a treatable cause of developmental delay in infancy. J Paediatric Child Health, 49(4): E348-349. doi: 10.1111/jpc.12158

6. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism: Fourth Edition. Boston, MA: Wadsworth (2004).

7. Hashim, O. H., & Adnan, N. A. (1994). Coenzyme, cofactor and prosthetic group β€” Ambiguous biochemical jargon. Biochemical Education,22(2), 93-94. doi:10.1016/0307-4412(94)90088-4

8. Hvas, A., & Nexo, E. (2006). Diagnosis and treatment of vitamin B12 deficiency. An update. Haematologica, 91(11), 1506-1512.

9. Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. (1998). Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. National Academies Press (US).

10. Kwong, J. C., Carr, D., Dhalla, I. A., Tom-Kun, D., & Upshur, R. E. (2005). Oral vitamin B 12 therapy in the primary care setting: a qualitative and quantitative study of patient perspectives. BMC family practice, 6(1), 8.

11. . Langan, R. C., & Goodbred, A. J. (2017). Vitamin B 12 Deficiency: Recognition and Management. American Family Physician, 96(6).

12.. Miller, A., Korem, M., Almog, R., & Galboiz, Y. (2005). Vitamin B12, demyelination, remyelination and repair in multiple sclerosis. Journal of the Neurological Sciences,233(1-2), 93-97. doi:10.1016/j.jns.2005.03.009

13. MΓΈllehave, L. T., Skaaby, T., Simonsen, K. S., Thuesen, B. H., Mortensen, E. L., Sandholt, C. H., … & Linneberg, A. (2017). Association studies of genetic scores of serum vitamin B12 and folate levels with symptoms of depression and anxiety in two danish population studies. European Journal of Clinical Nutrition, 71(9), 1054-1060.

14. National Heart, Lung, and Blood Institute (2011). What are the signs and symptoms of pernicious anemia? Retrieved from https://www.nhlbi.nih.gov/health/health-topics/topics/prnanmia/signs

15. Niculescu, M., & Zeisel, S. (2002). Diet, Methyl Donors and DNA Methylation: Interactions between Dietary Folate, Methionine and Choline. The Journal of Nutrition,132, 2333-2335.

16. Oh, R., & Brown, D. (2003). Vitamin B12 Deficiency. American Family Physician, 67(5), 979-986. Retrieved from http://www.aafp.org.libaccess.lib.mcmaster.ca/afp/2003/0301/p979.html

17. Osimani, A., Berger, A., Friedman, J., Porat-Katz, B. S., & Abarbanel, J. M. (2005). Neuropsychology of vitamin B₁₂ deficiency in elderly dementia patients and control subjects. Journal of geriatric psychiatry and neurology, 18(1), 33-38.

18. Vogiatzoglou, A., Smith, A. D., Nurk, E., Berstad, P., Drevon, C. A., Ueland, P. M., … & Refsum, H. (2009). Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study. The American journal of clinical nutrition, 89(4), 1078-1087.

19. Whitney, E., Rolfes, S., Hammond, G., & Piche, L. (2011). Understanding Nutrition (1st ed., pp. 332-334). Toronto: Nelson Education Ltd.


  1. C Mac on April 10, 2020 at 9:38 am

    Suchinyl?? Lmao

  2. hunati31 on April 10, 2020 at 9:39 am

    Spirulina is not a sea algae. It is a fresh water algae. More here:

  3. moog Dome on April 10, 2020 at 9:42 am

    Excellent informative video. Thank you so much.

  4. Hema Raj on April 10, 2020 at 9:42 am

    If thevitamin B12 increses what is the effect

  5. El autor on April 10, 2020 at 9:43 am

    Great video, it would help a lot if you speak louder or increase the volume somehow, also there’s a lot of oportunity for you to make the video simpler and easier to understand. Lots of love, thanks for the vid.

  6. Yuppers on April 10, 2020 at 9:44 am

    Your volume output is to low.πŸ‘Ž

  7. Sam Cav on April 10, 2020 at 9:44 am

    Excellent video thank you. Ive had tingling in my hands and arms for two years now and heart palpitations and extreme fatigue and its from having low b12 as im vegan and have been so for 4 years. My doctor has only just figured out that this is the cause of all of it. Im so happy to have an answer as this has been playing havoc with my life

  8. rachina gosai on April 10, 2020 at 9:45 am

    Does deficiency of B12 cause vitiligo?

  9. Ansh Thakur on April 10, 2020 at 9:47 am

    Plz mujhe koi bta sakta he mujhe yah saare symptoms the or mujhe boht jyada mental problem hone laga like health related sochta rehta tha kya yah iske hi symptoms he

  10. Sam Eer on April 10, 2020 at 9:48 am

    Areh mere phone ka speaker kharap hogaya kiya πŸ€”πŸ€”πŸ€”πŸ€”πŸ‘‚πŸ‘‚πŸ‘‚πŸ€³πŸ€£πŸ€£

  11. Mary May on April 10, 2020 at 9:49 am

    For only Three months, my very own daily episode of sleeping disorders has ultimately gone. The sleep treatment β€œFΞ±ntΟ…gΞ± FΞ±zΞ±m” (Google it) I used had saved me costs from obtaining prescription medication. Before all these, I can just get Three to four hours of excellent rest. Yet soon after adhering to this program, I managed to get Seven straight great resting hours. A year had passed, I could say that in many years these recent good sleep are the best I ever have. .

  12. Ella Mikaela on April 10, 2020 at 9:52 am

    How does the microwave kill vitamin B12? Is it not overcooking or heating food that results in less nutritional food?

  13. Krithika E on April 10, 2020 at 9:54 am

    what is normal level? i am at 174 pg/ml. having all the worst symptoms.

  14. Bill Kellum on April 10, 2020 at 9:55 am

    Yes, volume is way too low, and that is with high quality speakers.

  15. Kiran M on April 10, 2020 at 9:55 am

    First u should get vitamin b 12 such a lousey voice u should like someone forced u to work for this when ur suffering from high fever

  16. anthony walker on April 10, 2020 at 9:56 am

    Please fix the audio in this video!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  17. Cr0wnzzZ on April 10, 2020 at 9:57 am

    Vit B12 is produced by a special kind of bacteria. The animals are just fed with Vit B12. Thats why there is B12 in animal products
    But anyway great Video

  18. Kasha on April 10, 2020 at 9:58 am

    I never knew that about the microwave

  19. Enrique Rick Ramirez on April 10, 2020 at 10:00 am

    I’ve Become A vegan And I’m Having A hard time getting b12

  20. Erin on April 10, 2020 at 10:06 am

    I had an energy drink with B12 in it and it increased my mind’s clarity. I was looking into a possible deficiency.

  21. Gilgamesh Of Sumer on April 10, 2020 at 10:06 am

    my b12 deficiency was so bad that my fingernails were turning blue because of the lack of blood cells getting to them.

  22. Mohammed Azamshakib on April 10, 2020 at 10:06 am

    u voice is too 1stoo u should be take it out the B12

  23. LIZZY HUNTER on April 10, 2020 at 10:08 am

    Hi, thanks, so much for the help i never anyone show me how it works and what you need to help you , i have the B 12 need a shot cause my gut won’t take it , but now i know how it works and how i can help me in living better thanks, GREAT VIDEO , I CAN HEAR YOU FINE don’t know what they saying, you just speak softly cause your a girl is all , thanks

  24. omar meza on April 10, 2020 at 10:08 am

    i need ma daily vitamin T H C

  25. Artjoms Pugacovs on April 10, 2020 at 10:09 am

    Man sperm is rich in B12. That’s how I get my vegan wife to have oral sex.

  26. Gollammeister on April 10, 2020 at 10:10 am

    I’ve just been informed my folate levels too low I’m not gonna fret as there’s way worse stuff out there

  27. aavash simkhada on April 10, 2020 at 10:13 am

    i can’t walk till now properly , i used vitamin tablets,injections of B12 vitamin for 5 days but after 5 days i still can’t walk properly .plz help me

  28. Rhea on April 10, 2020 at 10:13 am

    This may also be helpful

  29. PdoubleEWdoubleE on April 10, 2020 at 10:13 am

    everything i need to know in one vid! greatly put together, thanks!

  30. lolo xoxo on April 10, 2020 at 10:14 am

    i been living with ibs since sep 2018 and jan 2019 i had the first insomia for a one night then i try to manage my ibs C by controlling my diet then hit by insomina again on august for 2 nights then whole november i was like zombie i cant sleep. i was so scared and finally went to doctor to check up that i have very less vitmain b12 . i so sad right now. i want my normal life back…

  31. Isobella Parsons on April 10, 2020 at 10:14 am

    My B12 deficiencies have always manifested as psychosis. Can you explain why this is a problem for me?

  32. Miss Alaana on April 10, 2020 at 10:15 am

    Thank you.

  33. Susie Bella on April 10, 2020 at 10:15 am

    Can’t hear properly πŸ™ your voice is too low !

  34. Srinivas Rao on April 10, 2020 at 10:15 am

    thanks a lot for the video.Taking enough vitamin B 12 now

  35. The Natural Health Blogger on April 10, 2020 at 10:17 am

    Home Active Vitamin B12 Test – Now available thanks to Forth with life.

    Check your active vitamin B12 levels with our quick, easy-to-use home blood test kit. You take a simple finger prick test and we’ll analyse your sample at one of our UKAS accredited labs in the UK.

    This B12 blood test kit measures the active form of B12 specifically (as opposed to total B12). This is the most accurate way to measure your available level of vitamin B12 and is the best early indicator of any possible deficiency.

    BUY NOW FROM FORTH LIFE AT: https://www.biomarkertracking.com/nhblog

  36. Scorpion Season on April 10, 2020 at 10:21 am

    Evrybody commenting about the volume need new headphones or to turn up the volume or buy a better phone with high quality speakers because I hear her just fine. And my volume is not all the way up. Thank you for this info !

  37. will on April 10, 2020 at 10:21 am

    no sound

  38. what ever on April 10, 2020 at 10:22 am

    thank you so much for this. the way you illustrated and explained everything made it very easy to understand. and never mind the negative comments about your voice,you have a lovely voice,you are just too soft spoken for some, maybe because of what they may be watching the video on,the volume levels might have been too low for some to hear your clearly.

  39. Gene Lariv on April 10, 2020 at 10:23 am

    I get my daily dose of vitamin B12 πŸ™‚

  40. It’s me Beth D on April 10, 2020 at 10:26 am

    Does it help with anxiety

  41. Kyle Leggat on April 10, 2020 at 10:30 am

    Is extremely low energy irrationality and headaches symptoms

  42. nisansala dilrukshi on April 10, 2020 at 10:31 am


  43. Srinivas Rao on April 10, 2020 at 10:32 am

    great video

  44. Joseph Stokes on April 10, 2020 at 10:32 am

    Yeah, she sounds like she has a bus to catch and is really in a hurry! LOL Question! What about sublingual B-12? I’m old and apparently my body cannot digest B-12 but I do get a monthly shot. Thanks for the video!

  45. Ansh Thakur on April 10, 2020 at 10:32 am


  46. Goldn Messi on April 10, 2020 at 10:32 am

    My whole 40 yrs of life doctors failed to recognize VitaminB12 mild, last 4 yrs extremely SEVERE deficiency..Hospital Emergency FAILED too, but charged me $5000. Finally current doctor (nurse practitioner) very first visit diagnosed B12 Def.. FEEL SUPER HAPPY, NORMAL, NERVES COMING BACK, SLEEP IS BACK. I can’t thank her enough.. Saved my life.. Severe case, Nerves all kinds of problem, memory loss, confusion, imbalance, headaches, dizziness, head spin (DANGEROUSLY LOW B12).. Yes, I was lifelong vegetarian, lactose INTOLERANT. Last 4 yrs, I didn’t sleep, tired, crash, head hung, body brains desperately sleeping giving up, but hear nerves keeps me painful awake deeply, it’s like zamby ghostly living with head nearve..No sleep created it’s own host of severe problem, aging, losing hair, gray hair etc… THANKS TO THE NEW Nurse practitioner & DOC, it was as simple as injecting B12 (3 inject one a week, 3 more to go, one monthly. So total 6 B12 inject). My whole life every doctor missed it..

  47. The Great Arkanum on April 10, 2020 at 10:33 am

    Great video very informative but very low volume hard to hear still thumbs up πŸ‘πŸ»

  48. Avinash Pardeshi on April 10, 2020 at 10:36 am

    The speaker has a deficiency for sure.. barely can we hear her!! πŸ˜†

  49. M R on April 10, 2020 at 10:36 am

    This video needs to be updated. A maintenance injection given only every 1 -3 months are for people who have a very *mild* form of genetic B12 deficiency. Moderate to severe cases require maintenance doses ranging from 1x per month, or 1x every two weeks, or even 1x per week depending on the severity. Please make sure you have your information together before stating something so careless that it could kill someone who relies on this info. Thank you.