Health

The green health bar on top, and the blue mana bar at the bottom.

Health (also known as HP) is a stat referring to the amount of life a unit or structure has. Death occurs when health runs out with no outstanding effects to survive. Health passively regenerates over time with health regeneration and can be restored through healing, life steal and spell vamp.

Health is represented ingame by a green bar situated next to the blue mana bar, with a fraction reading the current amount of health over the maximum amount possible. Current health is directly reduced by damage, maximum health reduction is usually percentage-based and will take from current health to represent such effect.

Each segment of the health bar represents 100 health.

Every unit and structure has their health displayed as a bar above their models.

Wards and similar champion summoned units have segmented health bars that each represent one life, but require another attack to remove.
Minions have a small non-descriptive bar.
Champions show a gauge on the health bar that illustrates the amount of health.
Large and Epic monsters, as well as structures display an exact health count along with a non-descriptive bar.
On Summoner's Rift, outer turrets have a gauge that represent plating.

Every champion starts with a certain base health, which increases by a small amount at each level-up.

Maximum health can be increased with items, abilities and runes, it stacks additively, and each bonus point acquired directly affects its statistic.

Gold Value

Health has a gold value of 2.67 per point.

Effective health

Effective burst health, commonly referred to just as effective health, describes the amount of raw burst damage a champion can receive before dying in such a short time span that they remain unaffected by any form of health restoration (even if the actual considered damage is of sustained form). It can however include any form of health gain (such as from Nasus' Fury of the Sands). Effective sustained health, on the other hand, would take into account also champion's health restoration.

Unless champion's resists aren't unnaturally reduced below zero, any effective health will always be more than or equal to a champion's displayed health in their health bar and it can be increased by buying items with extra health, armor and magic resistance.

Depending on the type of damage taken, we can also speak of physical effective health, magical effective health or mixed effective health. Depending on a behavior of such source of damage it is also possible to speak of effective health relative to given subject/source of damage, for example magical effective health versus poke. Many poke team compositions with mixed overall damage usually heavily rely on a poke consisting of prevalent magic damage. Maximizing primarily magical effective health thus might be a valuable counterstrategy to weaken their poking phase as teamfight initiation relies upon it.

Effective health is a measure of the durability of a champion, taking into account their health as well as their armor and magic resistance. 'Sheer' forms of effective health are defined as health plus 1% of health for every point of armor (or magic resistance). Contrary to their simple formulas, mixed effective health uses a bit more complex one. Because of this, mixed effective health is always subject to the damage source and the proportions between particular three damage composites (with pure damage being regarded as true damage). The formulae are as follows:

physical effective health = health × (1 + 0.01 × armor)
magical effective health = health × (1 + 0.01 × MR)

The formula for mixed effective health can be simply derived from the effective health : nominal health ratio which is always the same as ratio of damage dealt : damage taken (after application of resists):

$\pagecolor {Black}\color {White}{\rm {mixed\ effective\ health}}={\it {HP}}\times {{physical\ damage+true\ damage+magic\ damage} \over {{physical\ damage \over {1+0.01\times {\it {armor}}}}+true\ damage+{magic\ damage \over {1+0.01\times {\it {MR}}}}}}$

Note: One can include the penetrations in all of the above ideas by replacing penetration with a due amount of corresponding negative resist.

Physical effective health and magical effective health are effective against physical damage and magic damage, respectively. They correspond to the amount of damage that an enemy champion must output (not the amount you must take) to bring your health to 0.

Example: If you have 1000 health, then purchasing 90 armor will raise your physical effective health to 1900. Enemies will have to output 90% more physical damage than usual to kill you.

Health as a casting resource

See also Manaless

Edit Health is used as a resource to cast some — or all — of the abilities of some champions. It is critical to note that champions can never kill themselves due to ability casting. This is because they will be left at 1 health if their current health is below the cost.
Abilities that cost health can be used even if the champion does not have enough health to pay for the cost. With the exceptions of Ivern's Friend of the Forest, which cannot be used if he does not have enough mana or health for the cost, and Soraka's Astral Infusion, which cannot be cast if she lacks the mana for the cost or if she is below 5% health.

While these champions can cast their abilities more freely than most, their disadvantage is that frequent ability usage will bring them closer to taking fatal damage.
Health costs ignore invulnerability as well as effects that prevent falling below a certain health amount.

Champions who use their own health as a casting resource:

Champions that aren't manaless but use their own health as a casting resource:

It's worth noting that, besides Ivern and Sion, each of these champions have at least one ability capable of restoring their health:

Dr. Mundo's Adrenaline Rush, Infected Cleaver, and Sadism
Vladimir's Transfusion and Hemoplague
Zac's Cell Division
Soraka's Starcall and Wish
Olaf's Vicious Strikes and Reckless Swing

Note

Health costs will not be paid while under the threshold of Kindred's Lamb's Respite.

Health as scaling

Personal health

These use the champion's personal health pool to increase the magnitude of the ability. It may scale based on total health or only bonus health. By building health items you can receive more benefit and power from these abilities in most situations.

Maximum health

Current health

Missing health

Bonus health

Other