Pernicious Anemia (Rare Cause of Vitamin B12 Deficiency) Causes, Symptoms, Diagnosis, Treatment B12 Injection Frequency: How Often Should You Get a B12 Shot? Liv Hospital Pernicious Anemia and Other B Vitamin Deficiencies Struggling with B12 injection frequency? Here's what you need to know If you have Pernicious Anaemia (PA) or B12 deficiency due to autoimmune gastritis, NHS guidance is clear: You should