Add risers to the legs of the platform. If your bed's platform is the style that has four thin, distinct legs, you can purchase risers for the bed. These are small pieces that slip right over the bed's legs and add a few inches of height to your bed.
Place cinder blocks or large pieces of wood underneath larger legs. Some platform beds have wide legs and you cannot purchase traditional risers for this style. Instead, place something larger than the leg, such as a cinder block or piece of wood, to increase the height.
Use a box spring with your mattress. Platform beds do not require the use of a box spring, but this doesn't mean that you can't use one. Adding a box spring can add between 5 and 9 inches to the height of your bed.