Therefore, it does not necessarily imply that higher levels of serum vitamin B12 is due to a higher intake
Schedule (Once Weekly Injection) Upper limit: 12 mg per week is the highest dose used in the major published clinical trials (Phase 2 obesity, Phase 2 type 2 diabetes, and the Phase 3 TRIUMPH-4 and TRANSCEND-T2D-1 studies)
in this way, the body absorbs it quickly
Home Vitamin B12 is a powerhouse nutrient, vital for everything from producing red blood cells to maintaining healthy nerve function and keeping your energy levels stable
As to the aches and pains, breathlessness etc, this could be due to B12 needing potassium to build RBC, so I would check out low potassium symptoms and eat a banana or maybe two until you have fathomed it out
In terms of GI effects, it can cause gas, (sometimes with discharge), urgent or increased bowel movements, oily or fatty stools, loose stools, discolored stool, nausea, vomiting, diarrhea, and rectal and stomach pain