Health

Health: The player in Halo has a limited, non-regenerating health bar which can be fully restored by picking up health-packs; it is represented by the segmented blue rectangles in the graphic at the right. Running completely out of health will result in death, but having lower health doesn't impede player actions. A player's health can only be reduced if his shields have failed. If the player's health is low the game plays a low heart-beat sound.

Powerups
There are three types of powerups available in Halo:

Health packs
A single health pack will fully restore the player's health, but does not regenerate shields.

Active Camouflage
Reduces the player's visibility for a period of time, making him nearly transparent (the player becomes little more than a distortion in the air).

Over Shield
The over shield is a non-regenerating extra shield which functions on top of the regular shield, giving the player three times their normal damage capacity. When picked up, it takes approximately two seconds to completely charge, but during the charging period the player will be invincible. When it is active, the normal shield does not take damage until the over shield is completely gone (although any damage overlapping from something destroying the overshield, for example a grenade's explosion, will take the full rest of its effect on the original shield/health). If the over shield is picked up when the shield is down, the player receives a full charge and the effects of the over shield stay. In the single player game, the over shield is reduced only when the player is hit, while in the multiplayer game, it also weakens at a constant rate (see MJOLNIR MARK V battle suit).

Note: Unlike in Halo 2, If you get an Over Shield and Active camouflage at the same time, you cannot be seen.