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 or 25 with a life fruit). Each character starts with 100 maximum health (5 hearts), but that can be increased to a total of 400 (20 hearts) by using Life Crystals. It will take a total of 15 life crystals smashed and used to reach this level. After this, Life Crystals will no longer work, but the player's health can be increased further using Life Fruit, up to a maximum of 500. When a character's life reaches 0, death occurs.

Taking damage
The player loses health when they take damage from enemies, 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.

Enemies
Main article: Enemies

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

Environment
In addition to enemies, the environment of Terraria itself can cause damage to the player. Spikes 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 lighting them on fire leaving them to sink further into the lava to take additional damage.

Falling
Main article: Fall damage

Falling from a height of more than 25 blocks (50 feet) 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. All accessories can have mods that grant up to 4 defense in addition to their other bonuses and functions.

Preventing Drowning
These items are specifically for the purpose of avoiding getting stuck and drowning in water/other liquids.

Lava safety
These accessories are specifically for the purpose of mitigating or negating the effects of falling into lava.

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. The player will automatically start regenerating health after a short period if no damage has been taken, and it will do it faster while standing still or when near a regeneration aiding block (Heart Lantern or Campfire).

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. The cooldown is 60 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, enemies, or surviving long, difficult battles through constant item consumption.