Over the weekend, a new cheat was discovered that actually grants invincibility -- or infinite health -- for a limited time. To activate invincibility in GTA 5 simply enter the code below, depending on your console.
The cheats above enable invincibility for five minutes. Simply enter the code again after five minutes to reactivate invincibility and enjoy infinite health.
Cheats in GTA 5 must be entered on the gamepad. Use the D-pad to enter the directional commands. Once entered, a small confirmation will appear above the map.
For more information click here: Source: http://www.gamezone.com/originals/2013/09/30/gta-5-cheats-infinite-health-through-invincibility