it's safe to assume it is balanced as long as the wires aren't shorted to one another inside the cable. open up one end of it and check the colors that are connected to the pins. for example White might be connected to pin 3, red to pin 2 and the ground connected to pin1. make sure the other side of the cable has corresponding colors on the same pins.
it's techincally possible for a company to sells unbalanced cable, but not common. you can also use a DMM to check the cable to see if it's wired properly.