Hearts

Heart	Image	Worth	Additional Info	Unlocked By
Red Heart			Heals with Maggy's Bow. Error: The given collectible ("Humbling Bundle") does not exist. and Equality! can replace this with a 1+1 Free Heart.
Half Red Heart			Heals with Maggy's Bow.
1+1 Free Heart	File:1-1 Free Heart.png		Doesn't spawn naturally. Can only be found by using certain items or encountering certain rooms. Heals with Maggy's Bow.
Scared Heart			Identical to the standard Red Heart, but will run away as the player moves towards it. Heals with Maggy's Bow. Error: The given collectible ("Humbling Bundle") does not exist. and Equality! will not double this.
Soul Heart	File:Soul heart.png		Soul Hearts are blue hearts that are added to the end of the health bar. Soul Hearts are not permanent; once lost, they cannot be replenished, although new ones may be added.
Half Soul Heart				Template:Achv
Blended Heart	File:Red soul heart.png	//	Fills up a full red Heart Container, but will act as a Soul Heart when no Containers are free. If you are only missing half a heart, it will fill that half, and give you half a soul heart. Dark Bum will not collect this.
Black Heart	File:Black heart.png		When fully lost, it will damage all enemies in the room for 40 damage, similar to The Necronomicon's effect.
Eternal Heart	File:Eternal heart.png		When held until the next floor, Eternal Hearts will grant you a heart container. They will also give you a heart container if you collect two on the same floor.
Gold Heart			When a Gold Heart is lost, a few coins will be dropped around you. In Booster Pack #5, Gold Hearts now flash when depleted and will temporarily turn enemies golden like Midas' Touch.	Template:Achv
Bone Heart			Takes three hits to deplete and can be refilled with red hearts, but disappears permanently upon depleting.	Template:Achv

Notes

Unless an item effect specifically states it, a red heart always has the chance to be replaced by a Soul, Black, or Eternal heart.
Red heart pickups created by item, card, or pill effects can be forced to be spawned as Black or Eternal hearts instead by using the item, card, or pill in a relevant Super Secret Room.
If Isaac's health bar is filled with soul hearts, picking up a black heart will replace the topmost soul heart.
- If Isaac's health bar is filled up to 11 1/2 (Soul/Black) hearts with the last one being half a Black Heart, picking up a Black Heart will fill that one and convert a full Soul Heart to a Black Heart (therefore adding half a Black Heart and converting a Soul Heart).
- If Isaac's topmost heart is a half Soul Heart, collecting a Black Heart will complete it into a whole soul heart, and add half a Black heart.
- Collecting a Soul Heart with half a Black Heart left will complete the Black Heart, and add half a Soul Heart.

Trivia

There are unused graphics for Half Soul Hearts and Half Black Hearts that are never seen ingame.
- Half Soul Hearts were eventually added to the game as an unlockable in Afterbirth+.
Booster Pack #5 made Scared Hearts beat faster, making them slightly easier to spot. This was from this Steam Workshop mod by piber20.
Gold Hearts' appearance was changed in Booster Pack #5.