Pernicious anemia and vitamins: Best types and how to get enough Vitamin B 12 3000 mcg Injection, 100 mL Petco Vitamin B12 Deficiency Vitamin B12 deficiency happens when the body does not have enough vitamin B12. Vitamin B12 is important for making healthy red blood cells and keeping nerves Vitamin B12 Injections: Vital Therapy for Pernicious Anemia Pernicious Anemia (Rare Cause of Vitamin B12 Deficiency) Causes, Symptoms, Diagnosis, Treatment