power - microcontroller low battery indicator

I am powering a board and circuit with a 9V battery (those alkaline ones). And I would like to read the 9V battery to keep track of how much power it has left. I have read that I can do this with a voltage divider since most ADC input on uCs take 5V max. That's good but wouldn't the voltage divider itself draw power and make the battery drain faster? I am not going to constantly measure battery level.