can b12 injections cause stomach issues

According to British Society for Haematology (BSH) guidelines and NICE Clinical Knowledge Summaries (CKS), the primary beneficiaries include: Key patient groups who may require B12 injections include: Pernicious anaemia patients – requiring lifelong hydroxocobalamin 1mg intramuscularly every 2–3 months following initial loading doses Patients with gastrointestinal disorders – including those who have undergone gastrectomy or ileal resection, and patients with conditions affecting B12 absorption such as Crohn's disease or coeliac disease Strict vegans and vegetarians – though oral supplementation is usually sufficient unless malabsorption is present Elderly patients – who may have reduced gastric acid production affecting B12 absorption Patients taking certain medications – including metformin (MHRA advises monitoring B12 levels in long-term users, particularly those with risk factors or symptoms), proton pump inhibitors, and H2-receptor antagonists long-term [6] Individuals with neurological symptoms – such as paraesthesia, ataxia, or cognitive impairment related to B12 deficiency Pregnant women – with confirmed deficiency (hydroxocobalamin for malabsorption BPC-157 and Blood Pressure: Effects on Cardiovascular Health Pyridoxine BACTERIOSTATIC WATER:10ml Cyanocobalamin injection https://americanhistory.si.edu/sites/default/files/blog_files/a/6a00e553a80e108834017d3cc62156970c-800wi.jpg