The most common way that your character gets hurt is to take lethal damage and lose hit points.
What Hit Points Represent
Hit points are a manifestation of your ability to take heavy hits and keep on going.
Effects of Hit Point Damage
Taking damage doesn’t start to hinder you until you reach 0 hit points, at which you become disabled. If you take any additional hits you gain the Dying 1 state and go unconscious.
Disabled (0 Hit Points)
When your current hit points drop to exactly 0, you’re disabled.
You can only take 1 action per turn, and if it is more strenuous than simply moving you take fall unconscious and gain the dying state. Any healing applied reduces the dying state by 1 for every 5 points of healing.
When your character’s current hit points would drop to below 0 you begin dying. A dying character immediately falls unconscious and can take no actions. At the beginning of your turn you have Dying 1 or greater make a fortitude save with the DC equal to your level of Dying +10, if you fail you gain an additional level, if you pass you become stable. Upon reaching Dying a level of dying equal to 5+ your constitution modifier, you die.
When your character reaches a Dying level equal to 5+ their constitution modifier, they are dead. Characters can also be killed from having their constitution modifier reduced to -5.
Stabilizing and Recovery
At the beginning of your turn you have Dying 1 or greater make a fortitude save with the DC equal to your level of Dying +10, if you fail you gain an additional level, if you pass you become stable. You can keep a dying character from gaining a higher dying level by making them stable with a DC 15 Heal check. If any healing is applied to the dying character it immediately makes them stable and for every 5 points of healing received his dying state is reduced by 1. This healing must be applied all at once to remove a level of dying. For example a spell that only heals 4 damage would stabilize the character but not remove a dying level. Healing that raises the dying level to 0 makes him conscious and disabled. Healing that raises his hit points to 1 or more restores them to full capacity. A stable character will eventually regain consciousness and recovers hit points naturally. Characters can not be made stable if they are currently in a dangerous terrain or environment.
Recovering with Help
One hour after a character has been made stable, any other characters then attempt a DC 15 Heal check to make them conscious. They do not lose any of their Dying levels until they have either rested or obtained magical healing.
Recovering without Help
A wounded character left alone usually dies.
One hour after a character has been stable, they may attempt a DC 20 fortitude save to become conscious. They do not lose any of their current dying levels and are Disabled at 0 hit points. If they fail this save they gain another level of dying and may attempt a new check in one hour.
After taking damage, you can recover hit points through natural healing or through magical healing. Any hit point healing cannot go above your maximum hit points unless otherwise stated.
With a full night’s rest (8 hours of sleep or more for most characters), you recover 2 hit point per character level. Any significant interruption during your rest prevents you from healing that night. If you rest for a full 24 hours you instead recover 4 hit points per level and double the amount of ability damage.
There are many abilities and spells that can restore hit points.
Maximum Hit Points
You can never recover more hit points than you have lost, and you can never gain more hit points than your maximum.
Healing Ability Damage
Ability damage heals at a slower rate than hit points. Ability damage returns at the rate of 1 point per attribute for a night of rest. If you instead rest for a full 24 hours the amount increases to 2 points per attribute.
Temporary Hit Points
Certain effects give a character temporary hit points. Temporary hit points are used before regular hit points when calculating damage. In general, temporary hit points are not permanent and expire after a set duration.
Increases in Constitution Score and Current Hit Points
Increasing a characters constitution score grants 1 permanent hit point per level and increase their dying level capacity by 1. Any damage to constitution does the reverse.
Dealing Nonlethal Damage
Certain attacks, environmental effects and spells can cause non lethal damage. Unlike Lethal damage you track this damage separate from your hit points. When you have taken an amount of non lethal damage equal to your current hit points, you become disabled except you do not gain the dying condition if you take a strenuous action. If the amount of non lethal damage you take exceeds your current hit points you fall unconscious. Any further attacks against you become lethal damage.
Nonlethal Damage with a Weapon that Deals Lethal Damage
You can use a melee weapon that deals lethal damage to deal nonlethal damage instead, but you take a -4 penalty on your attack roll.
Lethal Damage with a Weapon that Deals Nonlethal Damage
You can use a weapon that deals nonlethal damage, to deal lethal damage instead, but you take a -4 penalty on your attack roll.
Healing Nonlethal Damage
You heal nonlethal damage at the rate of 1 hit point per hour per character level. When a spell or a magical power cures hit point damage, it also removes an equal amount of nonlethal damage.