Hey , Sorry for late answer , I just saw your question now ! Allright the minoxidil should used twice daily within at least 8 hours between the two applications ! So I do not recommend to use in the evening and one before sleeping , Since the half-life of minoxidil assume 8 hours ( I know its 4.2 in wikipedia but I do not rely on that source ) , So if you can't use it in the morning its better if you just use it around 2pm in the day and then 11pm or 12 pm before sleeping , But if you can do it in the morning that would be the best choice.