Death Saving Throw. Whenever you start your turn with 0 hit points, you must make a special saving throw, called a death saving throw, to determine whether you creep closer to death or hang onto life.
  • Roll a d20. This saving throw isn't tied to any ability score, but can be aided by spells and features that improve your chances of succeeding on a saving throw.
  • If the result is 10 or higher, you succeed. Otherwise, you fail. A success or failure has no effect by itself.
  • On your third success, you become stable. On your third failure, you die. The successes and failures don’t need to be consecutive; keep track of both until you collect three of a kind.
  • When you roll a natural 1, it counts as two failures. If you roll a natural 20, you regain 1 hit point and thus are no longer unconscious. 
Additional rules on death saving throws:
 
  • The number of successes and failures is reset to zero when you regain any hit points or become stable. 
 
  • If you take any damage while unconscious and stable, you stop being stable and must start making death saving throws again.
Instead of gambling for survival via death saving throws, you can heal or at least proactively  stabilize the creature with zero hit points.