are there side effects from b12 injections Vitamin B12: Overdose and Benefits of Vitamin B12 Shots
Description
Mol Cells (2012) 34:5736

Vitamin B12 deficiency often leads to nervous system damage that damages the optic nerve leading to your eyes

Summary: Feeling worse after a B12 injection typically reflects your body adjusting to replenished vitamin levels, triggering metabolic processes that may temporarily cause fatigue, headaches, or injection site discomfort

Remember how we said there was a significant caveat to the study mentioned above
Unfortunately, singly housing is not commonly reported
Good nutrition is good business
