http://www.livestrong.com/article/471331-are-mens-multivitamins-good-for-you/The most important difference is the amount of iron. You'll be fine because men's vitamins have less iron in them, women's have more.
If this were the reverse, someone on T still wanting to take the women's vitamins for whatever reason, I'd say absolutely don't (unless there is NO iron in it). Because after you're on T, your iron goes right where it should be from the increased red blood cells. So any more iron than that could be quite dangerous. If you ever got way too much while being on T (exactly what taking women's vitamins would do to you over a period of time), the only way to get rid of it quickly enough would be bloodletting (or taking some units out of you)... wouldn't be nice.
Actually, come to the heart of the matter, I don't feel a good vitamin for either gender should have iron in it at all. That should be a prescribed thing only if you actually don't have a regular amount... because too much really is very dangerous. Even when I wasn't on T, despite my excessive... female problems (I mean like the whole month kind of problems)... my iron was always normal, and without me taking multivitamins.
