Health

Health is the player's life in the game and is represented by hearts at the top of the screen (each heart represents 20 health). Each character starts with 100 maximum health, but that can be increased to a maximum total of 400 by using Life Crystals.

Taking Damage
The player loses health when he takes damage from monsters, environmental hazards, falling or drowning. After taking damage, the player will begin to flash. During this brief period the player is prevented from taking additional damage.

Monsters
Main article: Monster

Monsters such as Slimes, Zombies and Skeletons typically deal damage by touching the player. Other, more powerful monsters such as Fire Imps or Harpies can also damage the player via projectiles. Damage from monsters typically inflicts a knockback effect on the player, sending them flying through the air away from the source of the damage.

Environment
In addition to monsters, the environment of Terraria itself can cause damage to the player. Spikes, Cactus and the thorns that grow in the Corruption and Jungle areas hurt the player when touched. The heat from Hellstone and Meteorite blocks will also deal damage to the player. Lava is particularly dangerous as it causes serious damage but does not knock the player back, instead leaving them to sink further into the lava to cause additional damage.

Falling
Main article: Fall damage

Falling from a height of more than 25 blocks also causes damage to the player. Falls from greater heights will do more damage than short falls.

Drowning
Main article: Breath meter

Staying in water for too long will cause the player's health to swiftly drain away due to drowning.

Preventing Damage
Main articles: Defense and Armor

By wearing armor and equipping certain accessories players can increase their defense which decreases damage taken. In addition to simply decreasing damage, some items can mitigate or eliminate certain forms of damage.

Restoring Health
Lost health can be regained in many ways. If the player has access to a Nurse then they can ask her to heal them to full by paying her a fee based on how much damage has been taken. There are also several items that can be used to heal the player.

Note that healing effects will not exceed your maximum health and any healing beyond the maximum is lost. It is advisable to avoid overhealing when healing items are scarce.

Almost all consumable restoration items are affected by a shared consumable healing item cooldown, excluding the Regeneration Potion and Goldfish. The cooldown is 13 seconds long and begins when a consumable healing item is used. During this period the player is not allowed to consume any more consumable healing items. This prevents players from bypassing hazardous areas or enemies by constant item consumption.