Hearts, or HP, is the player's life force; running out will cause the player to die, losing a life or ending the game.
Players start the game with a specific number of "heart containers", the number varying on the character chosen.
Each Heart Container holds one full heart of HP, taking damage will empty one-half or one full heart container.
The maximum number of heart containers can be increased by consuming an HP up item or pill, up to a maximum of 12. Any heart containers found past that point can be spent at devil rooms, but not filled with hearts or half-hearts.
Empty heart containers can be filled using hearts or half-hearts.
Heart containers can be spent like currency in the Devil Room and can be emptied for cash at the blood donation machine.
Regular heart pickups are divided into Half Hearts and Full Hearts. These have about an equal chance of spawning.
These refill 1/2 of one heart container and can only be claimed if the player has less than full HP. These are common and can be found in a number of places.
These will refill 1 full heart container and can be claimed when the player has at least 1/2 heart missing, though this will cause half of the heart to go to waste. In addition to being found where normal hearts are these can also be purchased in shops.
Full Hearts cost 3 coins in the shop, 2 when on sale.
A number of treasures in game will increase your Max HP.
+1 Max HP
- Rotten Meat
- <3 (also acts as full heal)
- Blood Bag (also +1 Speed and heals some HP)
- The Halo (All stats up)
- Magic Mushroom (All stats up)
- Odd Mushroom (may have random side effects)
- Super Bandage (also adds 2 Soul Hearts)
- Health Up Pill (does not fill the added heart)
- Strength Tarot Card (Temporary)
+2 Max HP
- Bucket of Lard (empty, speed decrease)
- Raw Liver (Full heal, range decrease)
Soul Hearts are a rarer form of heart that may randomly appear instead of full hearts or can be found from drops/shops and won from slot machines and shell games in the place of hearts respectively.
Soul Hearts function as a form of armor for the player, absorbing damage that they take so that the player does not lose any HP. Once a soul heart is obtained, all normal damage removes soul hearts until their supply is depleted. Each soul heart adds a full container and can take a full heart's worth of damage before being lost.
Additionally, three soul hearts may occasionally be spent in the Devil Room to purchase an item.
Soul Hearts may be increased beyond the maximum visible level of HP and will still be counted even though they are not shown.
Soul Hearts in the shop cost 5 coins, 3 when on sale.
In the expansion The Binding of Isaac: Wrath of the Lamb, these special hearts can be received by any means that would otherwise yield a regular or soul heart but are rarer than Soul Hearts. Eternal Heart can also be found in the Chapel room. Acts as a soul heart until two halves become a whole, or the player moves onto the next floor (Also works when an item is used to achieve this effect such as Forget Me Now), turning it into a permanent heart container. The Prayer Card generates half of an Eternal Heart every time it is used. Fate item also adds an eternal heart. Eternal Hearts alone are not enough to prevent death. If you have no regular hearts (for example, playing with ???) and have an Eternal Heart you will still die if you lose all Soul Hearts.
Chance to find any heart pickup
- Completing rooms
- Champion enemies
- Chests (1 to few)
- Slot machines
- Shell games (2 at a time)
- Bosses (2 at the start, 1 when "Everything's Terrible" is unlocked. Extra heart is gotten from Champion forms.
Items that spawn Half Hearts
- Little C.H.A.D. (Spawns one in every two rooms)
Items that give Half Hearts
- Charm of the Vampire (1 Half Heart after killing 13 non-fly enemies)
- Isaac's Fork trinket
Places to find Full Hearts
- Heart secret room.
- Shop (costs 3 Pennies or 2 when on sale)
Items that give full hearts
- Yum Heart
Places where it's a chance to get either Half or Full regular Heart
- Blowing up a Blood Donation Machine (Chance of dropping one to a few)
Things that have a chance of spawning Soul Hearts instead of regular Hearts
- X Marks The Spot Rocks (1 or 2)
- Fortune Telling Machine (1)
- Red Chest. (1 or 2)
Items that Spawn Soul Hearts
- The Relic (one every 4 rooms)
- The Heirophant (2 Soul Hearts)
- Squeezy (2)
Things that Give Soul Hearts
- The Nail (6 room recharge, additional effects)
- Book of Revelations (6 room recharge, additional effects)
- The Mark (damage increase)
- The Pact (+2 SH, damage and tears increase)
- Rosary (+3 SH, additional effects)
- Super Bandage (+2 SH and +1 HP)
- Balls of Steel (2 Soul Hearts, added)
Things that give or spawn only Eternal Hearts
- Chapel Room
- Prayer Card