Loosing break fluid but no sign of leak. Where is it going? on 2000 Buick Century

Loosing break fluid but no sign of leak. I have to add fluid about once a month.I replaced both rear brake cylinders about 6 months ago.

Asked by for the 2000 Buick Century
2 answers
you ARE losing fluid, you just can't see it. because this is a safety issue, you need to take the car to a qualified techician ASAP. don't cause an accident due to your brakes failing!
It may leaks into the brake booster, but follow Overbys suggestion and get a shop check it throughly.

Zee