Cycles and breaks

There is no cycle and no break. This is replacement of a vitamin your body cannot build, so stopping simply lets the shortage return at the speed your gut is failing to absorb. Liver stores hold roughly two to five years' worth when full, which is why a shortage takes years to appear and why a break of a month changes little. If the cause is temporary, such as a course of acid-lowering medicine, the monthly dose can stop when the cause does, and the level is checked a few months later.