Not to be confused with the passive item Blood Bag.
A used IV bag, with blood inside and a needle ready.
Upon activation, half a heart of Isaac's current health will be depleted and a random amount of coins will spawn, and the IV can be used multiple times while only taking damage once because of the invincibility time Isaac undergoes when taking damage, allowing Isaac to use the bag two or three times before taking damage again.
- As with Blood Donation Machines, using the IV Bag will remove Eternal Hearts first, then Red Hearts up to one half heart remaining, and then finally Soul Hearts.
- Since using the IV Bag counts as the player taking normal damage, Isaac will gain a brief time of invulnerability as well. There are several uses for this:
- Quick use of the IV Bag in sequence allows for 2 uses at the price of only one half heart. From The Womb and onwards, the IV Bag can be used up to three times for each heart spent, due to the increased invincibility time from taking a full heart of damage.
- Before getting hit, quickly use the bag to only lose half a normal heart instead of half a soul heart (Useful for Maggy and Eve). The best application of this is probably when entering Curse rooms.
- Before getting hit by a damage that would cause a whole heart of damage (such as the maggot of a Chubber), quickly use the bag to only lose half a normal heart instead.
- Walking over the spikes in a Sacrifice Room will allow you to use the IV Bag to get a few coins for free due to the brief damage invulnerability. Note, however, that using the IV Bag (for the brief invulnerability) and then walking over the spikes will not spawn a chest.
- There is a critical money bug with IV Bag. Using IV Bag makes a short invulnerable time for the player, however, during that time coming and going through a door makes it continuous. There is a very short time for using IV Bag during the time (exactly when a coin in the room falls to floor), but it works. Video
- On floors where enemies do a whole heart of damage (The Womb and onwards), the IV Bag deals a whole heart of damage instead of 1/2 heart. The invulnerability period will also be longer, allowing the player to use the IV Bag three times before the invulnerability wears off.
- That said, if you only have 1/2 red heart and 1/2 spirit heart, using the IV Bag will kill you.
- Any invincibility-granting item, such as Celtic Cross.
- Any item which activates when the player has half a red heart left which does not count Soul Hearts, e.g. Whore of Babylon or The Polaroid. This is also useful for ensuring access to Boss Challenge Rooms.
- The Bloody Penny allows for chance to recover the cost of using the IV Bag on each use, especially if the item is used multiple times per each half heart lost. With enough heart containers it is possible to reliably use the two items to fill Isaac's health and obtain 99 pennies once they are both acquired, provided this happens before The Womb or after acquiring The Wafer.
- An IV bag is a medical object used on patients to store and hold blood and to administer medicine.
- IV is a short for "intravenous" which means "within or by means of a vein".