can b12 injections cause leg pain How to self-inject intramuscular vitamin - Overview When to Worry About Leg

doi: 10.1152/ajpcell.00043.2009 43 TaylorWEBhasinSArtazaJByhowerFAzamMWillardDHet al

MECHANISM CATEGORIES RESEARCH CONDITIONS SAFETY Side effects Limited human safety data Animal studies report wide therapeutic window Known interactions Methyl-donor depletion theoretical with chronic dosing (NNMT methylates nicotinamide using SAM) Contraindications Pregnancy/lactation (unstudied) REGULATORY STATUS FDA Not FDA-approved

Is it true we can actually absorb some B12 from our own microbiome

The reason is that a fixed reference dose gives a consistent, repeatable starting point: it lets supply be described accurately (how many applications a bottle provides), and gives first-time users a concrete default rather than having to research a range themselves