What conditions require B12 injections?

Additionally, taking B12 supplements is not advised if you have lupus, Crohn's disease, celiac disease, graves' disease, certain cancers, pernicious anemia, or certain infections. Antacids and some type 2 diabetes medications, among other prescription medicines, can lower the body's B12 levels.
How do you feel now that you've received a B12 injection?
injecting oneself The drug is injected into the muscle (known as an intramuscular B-12 Injection). You may experience some discomfort, bruising, or itching where the injection was administered. The majority of the time, this is mild and will pass quickly.