there aren’t too many side effects associated with common use of vitamin b12. the side effects that we are aware of especially at high doses are diarrhea peripheral vascular thrombosis itching transitory exanthema and urticaria. gastrointestinal side effects associated with parenteral cyanocobalamin or vitamin b12 given by injection have included dyspepsia nausea vomiting and mild transient diarrhea. these side effects are very mild or not present at all with oral vitamin b12. again the side effects can occur but usually at higher doses.
is nausea a side effect of taking vitamin b12?