arm sore after b12 injection Why do I feel worse a injection? Is intense whole arm pain

Less Common Side Effects

[1] Because intrinsic-factor-dependent uptake in the distal ileum can be absent in conditions such as autoimmune gastritis, pancreatic insufficiency, or bariatric surgery, the intramuscular or subcutaneous route bypasses gastrointestinal barriers and reliably restores serum concentrations

Now, some people can be more at risk of developing vitamin B12 deficiency

Delivered under clinician guidance, it focuses on supporting how the body maintains energy levels and physiological balance over time

By blocking NNMT, it shifts intracellular NAD+ and S-adenosylmethionine (SAM) levels, two cofactors tied to energy metabolism, redox balance, and gene regulation in laboratory models

The heavy consumption of ethanol for greater than 2 weeks has been reported to reduce the absorption of Methylcobalamin, vitamin B12