[10] [11] Intramuscular B12 injections (hydroxocobalamin or cyanocobalamin) bypass the digestive system, but UK product information (SmPCs) for hydroxocobalamin injections does list gastrointestinal disturbances, including diarrhoea, as possible adverse reactions, albeit rare
Sequences which could not be unambiguously assigned to a genus were labeled unclassified (Fig
So people at greatest risk for deficiency include those with low stomach acid (e.g., older adults and people on proton pump inhibitors or antacids) or low IF production (known as pernicious anemia), people on medications that interfere with B12 absorption (such as metformin), people who have had gastric surgery, those with GI conditions that impair nutrient absorption (like celiac or Crohn's disease), and people on vegan and vegetarian diets
Small observational studies have reported modest weight loss, but these typically lack adequate controls for dietary modification, exercise, and placebo effects