Check your brake pads, but if the light are on its something the computer in your truck is detecting, which may be fluid is low! Like Brett says, the only way you can loose brake fluid is your line needs to be replaced! Do not add fluid if the line is fine, can cause more damage if you do. Check to see if you are actually loosing fluid, if you are you can add until you get the line fixed, don't add to much. Add a little then check until reaches the line on dip stick. If line is worn get fixed very quick before any accidents happen
