Life gauge

The Life gauge is the bar at the top of the screen that indicates how healthy Snake is. As Snake gets injured it gets shorter until it runs out and then it's Game Over. Because of this it can become necessary to escape and hide if you become overwelmed. The gauge can be replenished by using rations. It is also a good idea to have rations as your equipd Item as they automatically replenish your health when you run out. When your health gets low the gauge turns orange and you start bleeding. this can be stopped with a bandage or by crouching or lying down.

O2 Gauge
when swimming or exposed to gas this gauge appears under the life gauge. It decreases over time and if you run out the life gauge decreases. However getting back into a normal environment resets it.

Stamina Gauge
This gauge is used in MGS3. This is a secondary gauge that has various effects on Snake. The main one being the fuller it is the quicker Snakes Life gauge recovers from his injuries. It decreases if Snake runs around or if he gets hit by a tranquilliser dart. Snake can increase it by eating food. Life medicine can be used like rations in previous games to replenish his life gauge.

Psyche Gauge
This gauge is used in MGS4. like the Stamina gauge its status affects the life gauge. When in a battle the gauge decreases. it increases If he gets out of a stressful situation or if he reads a book.