@tinaesims Supplements, multi-vitamins and probiotics are 3 different issues, I think.
Probiotics do seem to help me with the digestive issues while I am on the big 3. The flood of antibiotics is so devastating to the normal flora in the GI tract that I see a difference. If I lay off them for a week, it seems like I have constant, watery diarrhea. If I take them 3-5 times a week, alternating 2 different formulas, I just have frequent, loose stools. Live culture yogurt does seem to help, but less than the probiotic.
Multi-vitamins are the ones the docs think just mostly go out the liver and kidneys.
Specific supplements are targeted to an individual's specific needs. I take a divided dosage of calcium, magnesium and zinc because I am at high rick for osteoporosis and actually had too-low levels. The levels have stabilized and I am not showing any bone loss after doing this for over 10 years - I am doing well compared to my same-age cousins who don't take calcium. I also take a magnesium supplement to help regulate my (slightly) elevated blood pressure in lieu pf blood pressure meds I do not tolerate well. These both must be taken far from the time I take my antibiotics to avoid diminished effectiveness of the antibiotics, so I take them with breakfast and dinner. (I take my antibiotics at bedtime.)