In my humble opinion, I think they work most of the time. I would put it on a sliding scale, maybe 10-20% at worst, 80-90% at best. I think it depends upon
the amount of food/water you have on your stomach when taking the pill.
how quickly your body metabolizes the capsule/pill
the excercise done afterward that would change conditions for (1) and (2)
taking multivitamins before bed, when it would be absorbed slower into the body.
This is pure speculation on my part, what do you think?