I've heard 18 is when you should start, but I also agree you should go sooner if you're sexually active at a younger age. Not only that, but even if you're not sexually active, it's still good to make sure everything's working right. You can be a virgin and get a yeast infection, for instance. But you'll have symptoms, so don't worry you've got a yeast infection if you don't itch or burn (or smell)!