You can take the Help action to try to stabilize a creature with 0 Hit Points, which requires a successful DC 10 Wisdom (Medicine) check. A Stable creature doesn’t make Death Saving Throws even though it has 0 Hit Points, but it still has the Unconscious condition. If the creature takes damage, it stops being Stable and starts making Death Saving Throws again. A Stable creature that isn’t healed regains 1 Hit Point after 1d4 hours.