Prilosec b12 deficiency. . . to treat serious heartburn for four years, I developed a severe vitamin B12 deficiency. . webmd. . . In addition to blocking absorption of thyroid hormone and increasing the risk of osteoporosis, acid blockers like Prilosec and Nexium can cause Vitamin B12 deficiency. Results for the following 2 drugs: cyanocobalamin: Prilosec (omeprazole) . Symptoms of Vitamin B12 Deficiency including 51 medical symptoms and signs of Vitamin B12 Deficiency, alternative diagnoses, ... more