b12 injections sore arm at Home - Safety Guide for Self-Administration Best Vitamin B12 Injection Site:

"Living with Pernicious Anaemia and Vitamin B12 Deficiency" by Martyn Hooper Has several case studies

Vitamin B12 Medicine Interactions Chloramphenicol: bacteriostatic antibiotic can interfere with red blood cell response to supplemental Vit B12 Proton pump inhibitors: omeprazole and lansoprazole, etc., slow gastric acid release and may interfere with VIt B12 absorption from food H2-receptor antagonists: cimetidine, famotidine and ranitidine slow the release of hydrochloric acid into the stomach and interfere with Vitamin B12 absorption from food Metformin: might reduce absorption of Vitamin B12 due to altered intestinal motility, increased bacterial overgrowth, etc

Basantani, M

The resulting elevated concentrations of homocysteine and MMA are often found in patients with low serum vitamin B 12 and can usually be lowered with successful vitamin B 12 replacement therapy