Beware of the Rabid Coolant Monster! It Drinks Coolant! lol Yeah it could be a gasket if its overheating.... is it overheating when there actualy is coolant in the system?
its a head gasket, i have to top off my coolant with water almost every other day (depending on how much driving i have), so im burning coolant, and my mechanic friend told me its a leaky head gasket
it could be a number of things...blown head gasket, bad heater core (mine never leaked on the floor but i was losing coolant like no bodies business and couldnt even find a drip of coolant anywhere), bad radiator cap that wont hold pressure will blow out coolant when it gets too hot. check the oil and see if it looks like a milkshake because if it does than theres coolant in your oil. but you could just be burning it like custom89stang said. it could also be a combination of things like a bad thermostat that wont open and bad radiator cap. those are the easiest to check, so replace those and than bypass the heater core and if you are still losing coolant than its a head gasket, or could possibly be a water pump (on the shaft itself, and underneath at the weep hole). check everywhere that coolant flows through.