This may be the case for pregnant or breast feeding women and vegan or vegetarians

You should contact your GP if: You have been found to have elevated B12 levels on blood tests, particularly if levels exceed 1000 ng/L (approximately 740 pmol/L, though laboratory reference ranges vary) and you are not taking high-dose supplements You develop new symptoms after starting B12 supplementation, including persistent skin rashes, significant gastrointestinal disturbance, or unexplained symptoms You have underlying liver disease, kidney problems, or blood disorders and are considering B12 supplementation You are taking B12 supplements without medical supervision and have not had your levels checked, particularly if taking doses exceeding 2000 micrograms daily You experience symptoms that might indicate underlying disease, such as unexplained weight loss, persistent fatigue, jaundice, or abdominal swelling Call 999 or go to A&E if you develop severe allergic reactions following B12 injections, including difficulty breathing, facial swelling, or widespread rash, as these may indicate anaphylaxis, though this is extremely rare

The body regulates B12 absorption through intrinsic factor, a protein produced in the stomach that binds to B12 and facilitates its uptake in the terminal ileum
Can I use this if I have an autoimmune condition
This biological fact has led to a logical but oversimplified concern: if BPC-157 promotes blood vessel growth, could it help tumors grow too