A loose and lagging door hinge is a problem on your door frame. It means the door isn't properly sealed, leading to wasted energy and higher energy bills, and it will cause food and drinks within the refrigerator to spoil more quickly than they should. You can tighten the hinges to make the door level again, but the problem might also lie in the refrigerator itself not being level.
Unplug the refrigerator and clear out all items within it. If you can't preserve the items in coolers filled with ice, or if they have already spoiled, you will need to dispose of them.
Open the refrigerator and prop it up using a small stool or similar object that will fit underneath the door. Make sure the door is flush against the refrigerator; you may need a second person to hold it up.
Pry off the caps that cover up the door hinge fasteners, if such caps are equipped, using a flat blade screwdriver. There is usually a cap on at least the top hinge.
Tighten the fasteners on the door hinge. The fasteners can vary depending on the model; they may be screws requiring a screwdriver or bolts that need a small wrench.
Check the level of the refrigerator itself if you know the hinges are secure yet still lag, placing a level on top of the refrigerator. The air bubble within the level needs to be in the centre.
Turn the two screws that are at the bottom of the refrigerator's grille using a Philips screwdriver, giving each screw a full counter-clockwise turn. Do this until the air bubble in the level is centred.