Medikit

A medikit is an item that appears as large white box with a red cross. Picking one up will increase the player's health by 25% up to a maximum of 100%.

Medikits are not included in the items percentage displayed at the end of each level.

Data
In classic Doom, medikits are first encountered on these levels:

The IWADs contain the following numbers of medikits:

Doom RPG
Doom RPG contains two varieties of medikit (spelled medkit), "small" and "large". Small medkits restore 25 health points, and look like the originals except that their cross is yellow rather than red. Large medkits restore 75 points, and are red with a yellow cross.

Medkits in Doom RPG are not used as soon as they are picked up, but are added to the player's inventory to be used when needed.