Hearts

Hearts are Pick Ups that replenish Isaac's health. If Isaac runs out of both Red and Soul Hearts he will die and view his Last Will, unless he has Dead Cat, Ankh or 1UP.

If Isaac enters a room with a half Red Heart or less, a pool of urine (blood in Eve's case) will be formed under him. 

Red Hearts

Heart Containers

In order for Isaac to pick up Red Hearts, he must have Heart Containers that can be gained from a number of "Health Up" collectables or through completion of an Eternal Heart. Most characters also begin the game with at least one Heart Container, with the exception of ???, who is unable to gain Heart Containers at all, instead converting them into single Soul Hearts. Upon taking damage, Isaac will lose Red Hearts and be left with unfilled Heart Containers, which can then be refilled by the collection of Red Hearts. Any additional Heart Containers past the visible twelve will be unable to contain Red Hearts, and have limited use.

Heart Containers can be lost from the use of a Health Down Pill, certain Collectables, or being traded to the Devil.

Soul Hearts

Soul Hearts look similar to regular hearts but are blue with a faint white outline. They are a rarer form of Heart which may replace nonspecific appear instead of Red Hearts, or can be found in Shops. They have a high chance of spawning when a Tinted Rock is blown up.

Soul Hearts function as a form of armor for Isaac, absorbing damage that he takes so that he does not lose any Red Hearts. Once a Soul Heart is obtained, most damage removes Soul Hearts until their supply is depleted. Each Soul Heart adds a full Heart and can take a full Heart's worth of damage before being lost. Soul Hearts may be increased beyond the maximum visible level of Red Hearts and will still be counted even though they are not shown. The last half Soul Heart Isaac has will absorb any amount of damage while breaking, so taking a full Heart of damage with one half Soul Heart will not affect Isaac's Red Hearts.

Additionally, three Soul Hearts may occasionally be traded in the Devil Room in exchange for a Collectable (for characters without heart containers, like Azazel and ???, all devil deals are traded for soul hearts).

A Heart has a chance of spawning as a Soul Heart based on these rules:

1. 1/10 chance
2. 1/6 chance if playing as Eve (16.25%)
3. 1/10 if holding the Mom's Pearl trinket
4. 1/2 if holding the Mitre

Note that the extra chances for a Soul Heart to spawn are consecutive rather than additive, so (if not Eve) with Mom's Pearl, Isaac's chance would be 1 - (0.9 * 0.9) = 19% (rather than 20%) and with the Mitre his chance would be 1 - (0.9*0.5) = 55% (rather than 60%)

Eternal Hearts

Eternal Hearts are a type of Heart introduced in Wrath of the Lamb. They act as a Half Red Heart until Isaac picks up a second one or moves onto the next floor (also works when the Forget Me Now is used), in which case it will turn into a filled Heart Container. Eternal Hearts alone are not enough to prevent death. If Isaac has an Eternal Heart but no Red Hearts, he will still die if he loses all of his Soul Hearts. However, the Eternal Heart will remain if Isaac comes back to life with Dead Cat, Ankh or 1UP.

Eternal Hearts can replace nonspecific Heart Drops with a 1/50 chance or be granted by obtaining certain Collectable Items. They can also be found in the Cathedral-themed Super Secret Room. In addition, any nonspecific Hearts Spawned in that room will be Eternal.

It is possible to lose Eternal Hearts by getting hurt by enemies and Blood Donation Machines (including IV Bag). Blood Donation Machines take Eternal Hearts before any other type of hearts, but getting hurt by an enemy takes Soul Hearts first, then Eternal Hearts then Red Hearts. Unlike Soul Hearts, taking a full Heart of damage with just an Eternal Heart and Red Hearts will remove the Eternal Heart and half of a Red Heart, not just the Eternal Heart.

If you go into a Devil Room with no soul hearts and an Eternal Heart, and take a deal with the devil that doesn't kill you, you will lose the eternal heart.

Magneto will only attract Eternal Hearts when Isaac has unfilled Heart Containers.

Finding Hearts

Nonspecific Hearts

These Hearts have a chance to be Red, Soul or Eternal.

• 1 — Completing rooms
• 1 — Poop
• 1 — Fires
• 1 — Keystones
• 1 — Champion enemies
• 1 — Slot Machines
  • 1 — Portable Slot
• 1 — Beggars
  • 1 — Bum Friend
• 1 — Justice Tarot Card
• 1 or 2 — Bosses (2 at the start, 1 when "Everything's Terrible" is unlocked. An extra Heart is gotten from Champion forms.)
• 2 — Shell Games
• 0, 1, or 2 — Chests

Red Hearts

Items That Spawn Them

• 0.5 — Little C.H.A.D.
• 0.5 — Bloody Penny
• 2 — The Lovers Tarot Card

Items That Give Them

• 0.5 — Charm Of The Vampire
• 0.5 — Isaac's Fork
• 1 — The Tick
• 1 — Yum Heart

Locations

• 7 or 8 — Womb-themed Super Secret Room
• 1 — Shop

Soul Hearts

Items That Spawn The 1 — Crystal Ball (May give a Tarot Card instead)

• 1 — Fortune Telling Machine
• 1 — The Relic
• 1 or 2 — Red Chests
• 1, 2 or 3 — Tinted Rocks
• 2 — The Hierophant Tarot Card
• 2 — Squeezy

Items That Give Them

• 1 — The Nail
• 1 — Book of Revelations
• 1 — The Mark
• 2 — The Pact
• 2 — Super Bandage
• 2 — Balls of Steel Pill
• 3 — Rosary
• 3 — Guppy's Paw (in exchange for 1 Heart Container)

Locations

• 1 — Shop

Eternal Hearts

Items That Give Them

• 1 — Prayer Card
• 1 — Fate
• 1 — Maggy's Faith

Locations

• 1 — Cathedral-themed Super Secret Room

Gallery

The process that the game goes through to determine what type of Heart a nonspecific one will become.

If you use items which grant invincibility, or have soul hearts and make a deal for more heart containers than you have, you will have no hearts at all, and die on the next hit you take.

Related Achievements

"Maggy's Wig" - Have seven or more Heart Containers at once in a single playthrough.