WebMD recommends that a cut receive stitches if it is more than 0.25 inch deep, has jagged edges or gapes open. Any wound that extends past the skin and into deeper tissue may require stitches in order to aid in healing and to prevent infection.
Additionally, WebMD states that wounds to the face or those that may leave scarring should be stitched. Any wound over a joint or an area of the body that moves should receive consideration for stitches, as movement may impede the healing process. Lighter wounds, such as puncture wounds and cuts less than 0.25 inch deep, usually do not need stitches.