Older injection technique s taught pulling back the plunger to check for blood before injecting
Proceedings of the Society for Experimental Biology and Medicine, 167(2), 283-286
You may also be more likely to develop vitamin B12 deficiency if you have: Atrophic gastritis, in which your stomach lining has thinned Pernicious anemia, which makes it hard for your body to absorb vitamin B12 Conditions that affect your small intestine, such as Crohn's disease, celiac disease, bacterial growth, or a parasite Immune system disorders, such as Graves' disease or lupus You can also get vitamin B12 deficiency if you follow a vegan diet (meaning you don't eat any animal products, including meat, milk, cheese, and eggs) or you are a vegetarian who doesn't eat enough eggs or dairy products to meet your vitamin B12 needs
Cold injections are more uncomfortable and may cause increased injection site reactions