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With a full night’s rest (8 hours of sleep or more), you recover 1 hit point per character level. Any significant interruption during your rest prevents you from healing that night.
If you undergo complete bed rest for an entire day and night, you recover twice your character level in hit points.
Various abilities and spells can restore hit points.
Healing Ability Damage
Ability damage is temporary, just as hit point damage is. Ability damage returns at the rate of 1 point per night of rest (8 hours) for each affected ability score. Complete bed rest restores 2 points per day (24 hours) for each affected ability score.
Stable Characters and Recovery
On the next turn after a character is reduced to between –1 and –9 hit points and on all subsequent turns, roll d% to see whether the dying character becomes stable. He has a 10% chance of becoming stable. If he doesn’t, he loses 1 hit point. (A character who’s unconscious or dying can’t use any special action that changes the initiative count on which his action occurs.)
Healing that raises the dying character’s hit points to 0 makes him conscious and disabled. Healing that raises his hit points to 1 or more makes him fully functional again, just as if he’d never been reduced to 0 or lower. A spellcaster retains the spellcasting capability she had before dropping below 0 hit points.
A stable character who has been tended by a healer or who has been magically healed eventually regains consciousness and recovers hit points naturally. If the character has no one to tend him, however, his life is still in danger, and he may yet slip away.
Recovering with Help
One hour after a tended, dying character becomes stable, roll d%. He has a 10% chance of becoming conscious, at which point he is disabled (as if he had 0 hit points). If he remains unconscious, he has the same chance to revive and become disabled every hour. Even if unconscious, he recovers hit points naturally. He is back to normal when his hit points rise to 1 or higher.
Recovering without Help
A severely wounded character left alone usually dies. He has a small chance, however, of recovering on his own.
A character who becomes stable on his own (by making the 10% roll while dying) and who has no one to tend to him still loses hit points, just at a slower rate. He has a 10% chance each hour of becoming conscious. Each time he misses his hourly roll to become conscious, he loses 1 hit point. He also does not recover hit points through natural healing.
Even once he becomes conscious and is disabled, an unaided character still does not recover hit points naturally. Instead, each day he has a 10% chance to start recovering hit points naturally (starting with that day); otherwise, he loses 1 hit point.