How long does it take for vitamins B12 and d to get into ones system and start to work?

Depends. If you are taking vit d for bone issues, it can take quite a long time. If for other reasons like chronic pain or soe of the other claimed benefits, ther eis no definitive time period. As far as b12, if for anemia, red blood manufacturing cycles may take a bit of time as well befor eyou see results. Dont let this stop you as long as you andsd your physician agree on the dosages.