Tingling Sensation in the Hands and Feet
According to doctors at Mayo Clinic [11], consumption of high doses of vitamin B12 may cause tingling sensations in the hands and feet. While this is true, be careful about this. If you have tingling sensations in your hands and feet, it is more likely that it is caused by other underlying health conditions than vitamin B12 supplements. Get evaluated by a doctor.
Difficult, Rapid Breathing, Wheezing, and Difficulty Swallowing,
In very rare cases, vitamin B12 supplements may cause severe allergic reactions [12] that lead to anaphylaxis. This potentially life-threatening situation is often marked by symptoms such as swelling of the face and difficulty breathing and swallowing caused by swelling of the tongue and throat. If you experience this, call 911 immediately.
Conclusion
Vitamin B12 is a water-soluble vitamin. It dissolves in water and is easily passed out of the body as urine. This is one of the major reasons it is not toxic and rarely causes side effects. The body does not keep vitamin B12 it does not need. Most people do not experience side effects when they use vitamin B12. For those who do, the symptoms are short-lived and rarely serious. If you have any serious side effects when you take vitamin B12, you should seek urgent medical care. While extremely rare, vitamin B12 supplements may trigger bad allergic reactions in certain people.
References:
[1] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[2] https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
[3] https://lpi.oregonstate.edu/mic/vitamins/vitamin-B12
[4] https://www.drugs.com/sfx/vitamin-b12-side-effects.html
[5] https://www.drugs.com/sfx/vitamin-b12-side-effects.html
[6] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[7] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[8] https://www.drugs.com/sfx/vitamin-b12-side-effects.html
[9] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[10] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[11] https://www.mayoclinic.org/drugs-supplements-vitamin-b12/art-20363663
[12] https://www.healthline.com/health/food-nutrition/vitamin-b12-side-effects#side-effects