In fact, there is no indication to use vitamin B12 shots at all when you are not currently deficient in vitamin B12
Evidence-based management of anti-arrhythmic medications in the emergency department
This synthesis of vitamin B 12 is of no practical consequence due to its length, taking 72 chemical steps and giving an overall chemical yield well under 0.01%
By supporting nerve repair and reducing vascular inflammation, methylcobalamin and L-5-MTHF can help restore the sensitivity and function of these crucial autonomic sensors, potentially improving orthostatic tolerance
Kwatra S, Taneja G, Nasa N (2012) Alternative routes of drug administration- transdermal, pulmonary & parenteral
These two delaying factors are why patients with low B12 levels are often prescribed B12 shots instead of oral supplements