SRD:Loss of Hit Points
From D&D Wiki
|This material is published under the OGL|
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
At –10 or lower, you’re dead.
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)
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.
Dying (–1 to –9 Hit Points)
A dying character immediately falls unconscious and can take no actions.
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.