Brake Question

I have noticed that over the past 8 months that my brake fluid is going down slightly, I tend to lose about 1/2 " of fluid over the span of about 8 months, can anyone tell me if this is normal and can just a sign of the brake pads wearing down or if would be a leak somewhere, and if it is a leak where would the trouble spots be, I dont see any kind of leaks around the master cylinder or around the calipers.Thanks