Quick question about hair dye, easy 10 points?

my natural hair color is a light brown, for the past year I have been dying it a light blonde (not platinum) but a fair bit lighter with cheap $10 boxes from loreal. It works pretty well and i color it every 3-6 weeks to touch up roots and all. The thing is, i'm a bit sick of being blonde and I want to go darker brown, darker than my natural color. What would happen if I used a loreal brunette shade, would it not come out correctly? Because I know it's advised not to change shades drastically like that. What do I do? Do I wait? get it done professionally? Any and all answers are appreciated, thanks