Unless you have a specific health problem, it's a waste of time and money. If you eat a varied balanced diet, you have no need for a multivitamin. Now if you happen to have a specific health problem, like iron deficiency then a supplement of iron would be in order. Now it can be unhealthy to take multivitamin as some accumulate in your system and can cause problem Hypervitaminosis A (too much vitamin A) and in some cases too much of a vitamin just mean you're excreting it. Vitamin C in high doses will pass out of your system without being used at all.
Eat right and unless you have a specific health problem the can be addressed with vitamins, save your money.