Vitamin B12 and vitamin B2 are both water-soluble vitamins from the B-complex family. They do not interfere with each other's absorption, metabolism, or excretion. Instead, they have a synergistic relationship; vitamin B2 is actually required to help convert vitamin B12 into its active form so the body can use it properly.
This is a companion discussion topic for the original article at https://de.patient.info/medication-interactions/vitamin-b12-and-vitamin-b2-interaction