Fixing a loose sliding door handle is not as difficult as it may seem. The first step is to identify what type of sliding door handle you have. Depending on the type, there could be several different methods for securing the hardware and preventing further loosening. If your handle has a single screw at the back, unscrew it and check if any part of the frame or other components are damaged or worn out. If so, replace them with new ones before reattaching the screws securely into place. You can also use some lubricant such as WD-40 to reduce friction between moving parts and ensure that they fit snugly together without coming apart easily in future. Finally, inspect all hinges and latches around your sliding door to make sure that they too are working properly before attempting to close up once more.