Checking brake fluid is a quick under-hood glance that can catch worn pads or a leak early. It is different from changing the fluid - checking is about keeping an eye on the level and condition. Here is how often to do it and what to look for.
A quick check schedule
A good habit: glance at the brake fluid reservoir every month or so, and always check it at every oil change. It takes seconds - the reservoir is translucent with MIN and MAX marks, so you can read the level without opening it. Regular checks catch problems long before the dashboard warning comes on.
What the level tells you
A level slowly dropping toward MIN usually just tracks pad wear - as pads wear, fluid moves out to the calipers - see why is my reservoir low. But a fast drop, or a level below MIN, can mean a leak, which is urgent - see brake fluid leak signs. Do not just top it off without knowing why it dropped.
Also check the condition
While you are looking, note the color. Clear-to-amber is healthy; dark brown or black means it is contaminated and due for a flush - see contaminated brake fluid. This visual check hints at when a full change is needed even before the calendar interval.
Checking vs changing
Checking is monthly/at oil changes; changing (flushing) the fluid is every 2-3 years - see how often to change brake fluid. Never open the cap unnecessarily (that lets moisture in). Pair well-maintained fluid with quality pads and hardware.