vitamin b12 injections how often to take B12: Frequently Should I Get It? B12 Shot - IV Concierge

Individuals who have had gastrointestinal surgery, such as weight loss surgery, may also have fewer cells through which to secrete stomach acid and intrinsic factor, inhibiting B12 absorption

J Comp Pathol 163, 1-5

Heavy smokers and drinkers can also have low levels of B12

Also, make sure you're giving any medications as prescribed by the vet

Prolonged stress causes the sympathetic nervous system and may raise the level of mast cell degranulation and, as a result, trigger inflammatory reactions and histamine levels

This means that livestock can be sold for slaughter even the day immediately after treatment, should market prices suddenly increase