SRD:Loss of Hit Points

Loss of Hit Points
The most common way that your character gets hurt is to take lethal damage and lose hit points

What Hit Points Represent
Hit points mean two things in the game world: the ability to take physical punishment and keep going, and the ability to turn a serious blow into a less serious one.

Effects of Hit Point Damage
Damage doesn’t slow you down until your current hit points reach 0 or lower. At 0 hit points, you’re disabled.

At from –1 to –9 hit points, you’re dying.

At –10 or lower, you’re dead.

Massive Damage
If you ever sustain a single attack deals 50 points of damage or more and it doesn’t kill you outright, you must make a DC 15 Fortitude save. If this saving throw fails, you die regardless of your current hit points. If you take 50 points of damage or more from multiple attacks, no one of which dealt 50 or more points of damage itself, the massive damage rule does not apply.

Disabled (0 Hit Points)
When your current hit points drop to exactly 0, you’re disabled.

You can only take a single move or standard action each turn (but not both, nor can you take full-round actions). You can take move actions without further injuring yourself, but if you perform any standard action (or any other strenuous action) you take 1 point of damage after the completing the act. Unless your activity increased your hit points, you are now at –1 hit points, and you’re dying.

Healing that raises your hit points above 0 makes you fully functional again, just as if you’d never been reduced to 0 or fewer hit points.

You can also become disabled when recovering from dying. In this case, it’s a step toward recovery, and you can have fewer than 0 hit points (see Stable Characters and Recovery, below).

Dying (–1 to –9 Hit Points)
When your character’s current hit points drop to between –1 and –9 inclusive, he’s dying.

A dying character immediately falls unconscious and can take no actions.

A dying character loses 1 hit point every round. This continues until the character dies or becomes stable (see below).

Dead (–10 Hit Points or Lower)
When your character’s current hit points drop to –10 or lower, or if he takes massive damage (see above), he’s dead. A character can also die from taking ability damage or suffering an ability drain that reduces his Constitution to 0.