Healing items

"First to aid, last to die."

- Bill

Healing items are those used to restore lost health, be it a temporary health boost or a permanent restoration. They can be found in ambulances or randomly throughout levels, but are most often found inside of first aid stations. First aid stations may contain up to four bottles of Pain pills, but there is also a chance that they contain First aid kits instead, depending on how well the Survivors are doing and the difficulty level. First aid stations found in safe rooms and at finales always contain First aid kits.

First aid kit
"Can everyone stop a sec? I'm gonna heal!"

- Zoey

The First aid kit, colloquially known as a med kit or health pack, is used to heal any damage the Survivors take during a campaign. When carried by Survivors, it is held on like a backpack with no visible straps holding it.

First aid kits can always be found inside of safe rooms, and during the finale of a campaign. They can also be found in first aid stations and in random places anywhere else throughout the campaign, though this is very rare. On Expert difficulty, most first aid kits found in the level itself will be replaced by pain pills. The only sure way to get health packs on Expert is to grab one in the safe room or at the finale. Finding one in the level itself is extremely rare and should not be wasted.

In Versus mode, if the players heal each other, the director will spawn more health kits within the map. Keep in mind if you are the first team to play as the Survivors, whatever health kits you caused the director to spawn will also be available to the other team when it's their turn. This could be a hazard as the Infected team could use it to their advantage for when they become the Survivors and learn the locations of the spawned health kits when dead or as a ghost in spawn mode.

In Left 4 Dead 2, the player has the choice to pick up a Defibrillator or Ammo Upgrades instead, which can be used to revive dead teammates or ignite/explode the Infected with special ammunition.

First aid kits can randomly be spawned by the Director when Survivors are obviously hurting and low on/have no healing items. They can be spawned in places which the Survivors have recently searched, depending on the whims of the Director.

In The Passing, First aid kits can sometimes be recovered from dead Fallen Survivors.

Usage
It takes five seconds to use the first aid kit to heal yourself or another Survivor, during which you cannot defend yourself in any way. However, in Left 4 Dead 2, if you are under the effects of Adrenaline while healing yourself or another Survivor, it will only take three seconds. Instead of restoring a set amount of health, First aid kits will only restore 80% of damage the Survivor has taken. For example, if a Survivor has taken 70% damage, using a First aid kit will add 56% (80% of 70) to the Survivor's health, bringing the Survivor to 86% health. This healing is not based on any temporary health a Survivor might have after taking Pain pills, and will remove any extra health gained by them. Survivors healing after incapacitation work on the same rules, and thus, always receive 80 health points. Note that First aid kits can never bring a Survivor back to 100% health, so using more to try to do so is a waste.

As a weapon
A Survivor can use their melee attack while they are holding the First aid kit, though the only time you might consider doing so is if you were in the middle of healing yourself or another Survivor and you got attacked suddenly. If that happens, it would be best to use your melee attack to push the attackers away to give yourself time to switch to another weapon. Needless to say, using your melee attack while holding a First aid kit does the same amount of damage as any other melee attack, but it's easy to get caught up on trying to heal another Survivor (both the melee attack and healing another Survivor share the same button). Pistols would generally serve better in a serious fight.

Defibrillator
"AHH, stop shockin' me!"

- Nick

The Defibrillator, also referred by Survivors as "chest paddles", is an item used only in Left 4 Dead 2. It can be used to revive a dead Survivor and can only be used once. For balancing purposes, Survivors cannot carry a Defibrillator and First aid kit at the same time.

Official Description
Bring teammates back from the dead. Like the First Aid Kit, a Defibrillator Unit is a one-time use item. Defibs can resuscitate fallen teammates, and take three seconds to use.

Usage
To use the Defibrillator, a player must first equip it. This will reveal where the closest corpse is via a faint red glow. They must walk up to the corpse and hold either of the attack buttons. A charging meter, which takes three seconds to complete, is shown. Then there is a short burst of electricity, and the Survivor has been successfully resurrected. The revived Survivor comes back with 50 health (which is permanent health that doesn't drop like temporary health gained when being revived after being incapacitated) and can pick up all dropped items except for a secondary weapon before continuing. There will be a message on the left side of the screen informing everyone who brought whom back to life. It is recommended most Survivors pick up First aid kits and just have one Survivor have a Defibrillator at a time. The Defibrillator can become especially useful in Expert difficulty and Realism Mode, where a Witch is able to instantly kill a player, and since in Realism Mode (along with Versus Mode), there are no rescue closets. A Defibrillator can be used on any Survivor corpse, even if they have already been saved from a rescue closet (even your own corpse); the player's "consciousness" will then enter the body of the newly-revived teammate. It should be noted that you cannot revive someone as long as somebody is standing over the body. (This has been fixed, now when a Survivor is revived, the Survivor in rescue closet will disappear; and if a Survivor is rescued via rescue closet, the corpse disappears. This would keep 4 Survivors maximum at anytime.)

Depending on the situation, there may be times when it is a good strategy to intentionally kill a teammate, then revive them with the defibrillator. For example, killing a player who is black and white then using the defibrillator on them will reset their incap count, and restore them to 50 permanent health. Such tactics can be crucial on the higher difficulty settings where health packs & pills/adrenaline are at a premium.

AI Survivors cannot pick up or use Defibrillators. The only way they can hold it is if a human player was controlling a Survivor in an online game, and picks one up, but then quits or goes idle, leaving the AI to take over the Survivor holding the Defibrillator. They will not use it, and will immediately swap it for a First aid kit if one is available lying around.

If someone dies from a hanging death (holding onto a ledge), they cannot be revived at all, since they fall and become a ragdoll. However, if they are killed by a molotov or pipe bomb from another Survivor, rather than losing their grip, the body may fall into an accessible area, (such as in the finale of Dead Center, from the stairs to the first floor) and the fallen teammate can be revived from there.

In reality, defibrillators cannot revive somebody from the dead. Specifically, they are used to reset a heart's rhythm, and are not to be used during a flatline; in addition, clothes must be removed or cut off to access a bare chest and CPR must be used for several minutes before the process occurs. Seeing as both games are modeled after stereotypical B-list movies, though, this exaggerated use of defibrillators is rather fitting.

Defibrillator behavior in Versus Mode was changed slightly as of the June 18th 2010 update: The Director now spawns Defibrillators based on map length, and are limited to only one spawn per map. Reviving a dead Survivor also results in a 25 points penalty.

Pain pills
"Pills here!"

- The Survivors

Pain pills, unlike the First aid kit, will only give the user 50 temporary points of health when taken. When carried by Survivors, it is held on the Survivor's right hip, probably on the belt.

Pain pills can be given to teammates by pressing the melee button (right click on PC or left trigger on 360).

Since the health from Pain pills is only temporary, it will slowly decrease over time, dropping one point every few seconds until all of the temporary health is gone. The Pain pills you take will restore your movement speed and stop you from limping for as long as your total health is above (or equal to) 40%. Since temporary health goes down one point every five seconds, the effects of Pain pills will last four minutes and 10 seconds, assuming no damage is taken.

Keep in mind that taking damage when both permanent health and temporary health exist, permanent health will be taken first. If you have temporary health and your actual health drops below zero, your temporary health will continue dropping until it reaches 1%, where it will stay until you either heal or get incapacitated.

Adrenaline Shot
"Grabbin' a shot!"

- The Survivors

Adrenaline Shots are included in Left 4 Dead 2, occupying the Pain pills' inventory slot.

Official Description
An adrenaline shot gives you a fifteen-second health and energy boost that lets you run faster, use items in half the time, and run through zombies without getting slowed down by their attacks.

Usage
Upon injection, the user gains 25 temporary health. For 15 seconds, they move faster, do not experience melee fatigue, are immune to the Horde's slowing melee attacks and their speed isn't affected by water.

It also increases the speed of using First aid kits, reviving Survivors and reloading and switching weapons and items.

As temporary side effects, the user also experiences tunnel vision and sound becomes monophonic, hindering their ability to determine the direction from which a sound came. This can become annoying during a split screen campaign if one player uses Adrenaline too much, as the monophonic penalty affects both players.

The Adrenaline Shot is always seen in the Crescendo Event in "The Park".

This item could become valuable at the end of a finale, where Survivors must reach a rescue vehicle while being impeded by the Horde.

Like Pain pills, the Adrenaline shot can be passed to a teammate by using the melee button.

The Adrenaline shot is a very precious item during a Scavenge game, as it can increase your speed and the speed of the gas pouring by roughly 50%. Generally two shots will be spawned during a Scavenge game. Wasting them can be a big mistake.

The Adrenaline Shot in-game is based on real-life emergency "EpiPen" auto-injectors, which are filled with synthesized epinephrine: literal adrenaline. The adrenaline acts as a vasoconstrictor, slowing the body's allergic response and delaying the victim from going into anaphylactic shock. Since as much as 15% of the United States population is considered 'at-risk' for anaphylaxis, it is not beyond the realm of plausibility for the adrenaline shots to be found as often as they are, particularly if they were included as part of CEDA's Emergency Relief Supplies.

Achievements
See main article: Achievements

Behind the Scenes
Early screenshots show that the first aid kit had a more boxlike shape, didn't look like it was made out of soft materials and had a carrying handle at one time. This design can still be seen in the final version's first aid kit icon.

Early videos showed it was possible to share med kits like pills instead of healing them (as seen as in this video at 0:36).

The placeholder for the adrenaline shot was nothing like a syringe, rather a re-skinned pain pills model with a yellow bottle. The texture can still be found in Left 4 Dead 2 files. Then it became an syringe similar to the one used in the HUD before the current look for adrenaline.

Likewise, the defibrillator's world model placeholder was a re-skinned first aid kit model. Its textures can still be found in Left 4 Dead 2 files.