b12 injection side effects urine Vitamin B12: All You Need to Know Compounded Methylcobalamin (Vitamin B12) Injection,

For individuals sourcing either compound from unregulated online vendors, additional risks include contamination with unknown substances, incorrect dosing due to inaccurate labelling, and the use of non-sterile injection equipment, which can lead to serious infections including abscess formation or sepsis

PMID: 35337625

Worsening macrocytic anemia : B 12 deficiency may also cause a macrocytic (megaloblastic) anemia BUT, in the presence of folate supplementation, this anemia may be masked so that B 12 deficiency may present with exclusively neurologic features

Treating true deficiency can improve deficiency-related symptoms (including anemia-related fatigue and neurologic issues) (see the NIH ODS Vitamin B12 fact sheet )

Tests like vitamin B12 levels and blood counts help guide the dosing