Bee, according to my Gastro guy, vitamins are OK with a couple of caveats.
First, it is DEFINITELY possible to overdose on vitamins, and your kidneys have to get rid of the excess "stuff" that your body couldn't use. Therefore, only take vitamins up to the recommended daily allowance level. The mega-dose vitamins are NOT for people with kidney, liver, or pancreas problems. It is ABSOLUTELY possible to overdose on vitamins. Therefore, read the label regarding normal doses.
Second, watch out for the substrate of the vitamin tablet. For non-chemists, a substrate in this context is what you use to mix in with something else to act as a carrier for the something else. If you have a pharmaceutical substance with microgram dosages, the pill of that chemical in pure form would be too small to pick up - but if you add a substrate to turn into a tablet, you can handle it. In some vitamins, the actual chemicals are suspended in fish oil. That was what messed up my liver, by the way. I have an oil sensitivity - not quite as pronounced as an allergy, but we still don't get along well. (Thank goodness for tuna packed in water!) The substrate is supposed to be inert, but if you are allergic or sensitive to it, it can hit you hard. And some substrates are solid, not liquid. You can often identify them when you see some phrase like "and 45% of XYZ as an inert filler." XYZ, whatever it is, is your substrate.
Third, UNLESS you have specific absorptive deficits in your stomach and intestines, or you eat really CHEAP and LOUSY food, your body can absorb all of the natural vitamins without assistance. Which is why vitamin supplements are normally not needed. If your doctor actually prescribes some kind of vitamin, you might correctly infer that either (1) s/he thinks you have a digestive deficit or (2) the vitamins are a test to SEE if you have such a deficit or (3) you have an enzyme deficiency that causes your body to be inefficient in processing the natural vitamin, so you need a higher dose to be sure you get enough of the particular vitamin.
So if you wanted to take vitamins, go right ahead. Just don't take too many.