B12 injections are great to maintain proper cardiac(heart) function as well as vital to neurological(brain) function. B12 helps with DNA and red blood cell production. They have also been researched to help with energy levels, mood, concentration, improve metabolism and helps with weight loss, boosts immune system and improves sleep patterns.
B12 injections are prescribed and given in the muscle.
Vitamin B12 deficiency is common and because B12 is only found naturally in animal food sources, most vegans and vegetarians are deficient. It's important to note that if you do consume meat and animal food sources, you can still be deficient if your body doesn't absorb the b12 that well.
Untreated B12 deficiency can lead to neurological issues as well Pernicious anemia(when your body doesn't have enough B12 to produce the red blood cells it needs).