feeling worse after b12 injections Why Do I Feel My Injection Vitamin B12 deficiency signs and

These antibodies to intrinsic factor can be detected several years before the onset of symptoms of pernicious anemia.[ref] What triggers autoimmune gastritis

Cyanocobalamin (cyanocobalamin): Side effects, uses, dosage

Side Effects, Warnings, and Monitoring Most people tolerate cyanocobalamin injection, but side effects can occur

Allergic Reactions: Rare, but monitor for rash, urticaria, or anaphylaxis

The cardiovascular and respiratory side effects include chest pain, tachycardia (increased heart rate), heart palpitations, low blood pressure, and chest tightness, cough with or without production of pink frothy sputum, wheezing and difficulty breathing