NEVER!!! If you don't want to end up like Kojak after six months.
Well, the only possibilty is to decrease the concentration very, very slowly, and simultaneously to jump on a strong anti-androgen (dutasteride) that should keep your hair alive, if you encountered some "mishap".
If you abruptly jump from 15% to 5%, you will go through a disastrous shed. And only a part of the lost hair (those hairs that you wouldn't have normally lost without minoxidil) will grow back. If you used dutasteride and if you encountered such a terrible shed, you should (in theory) keep virtually all your hair alive, but only if you return back to the previous concentration.
