Medicine

Medicine is an item that is able to restore Link's life, magic, or both. It first appears in A Link to the Past, though the Water of Life, which fills a similar functional role, did appear earlier in The Legend of Zelda & again in The Adventure of Link, where it served a different role.

A Link to the Past
There are three types of Medicine that appear in A Link to the Past:

Medicine of Life
The Medicine of Life is red in color and can be purchased for 120 Rupees from the Magic Shop in the Light World and for 150 Rupees from several other shops in the Light World & Dark World. It completely restores Link's life meter. Link must have an empty Magic Bottle to store the Medicine of Life when he purchases it. The Witch's assistant regularly gives Link a sample of the Medicine of Life whenever he speaks to her.

Medicine of Magic
The Medicine of Magic is green in color and can be purchased for 60 Rupees from the Magic Shop in the Light World or acquired for free by throwing an empty Magic Bottle in the Mysterious Pond at the Waterfall of Wishing. It completely restores Link's magic meter. Link must have an empty Magic Bottle to store the Medicine of Magic when he purchases it or acquires it from the Waterfall of Wishing. It is particularly handy in the cave that contains the Cane of Byrna and in Turtle Rock.

Medicine of Life and Magic
Also known as Cure-All Medicine, the Medicine of Life and Magic is blue in color and can be purchased for 160 Rupees only from the Magic Shop in the Light World. It completely restores Link's life & magic meters. Link must have an empty Magic Bottle to store the Medicine of Life and Magic when he purchases it.

Link's Awakening
The Medicine in Link's Awakening is officially known as Secret Medicine.

Secret Medicine
Link can obtain Secret Medicine by purchasing it from Crazy Tracy's Health Spa. In Link's Awakening DX besides buying it from Crazy Tracy's Health Spa, Link can also find it in various treasure chests. Such treasure chests can be found in the Face Shrine, Eagle's Tower, and Turtle Rock. Unlike the Medicine of Life in A Link to the Past that has to be manually selected & used, it automatically takes effect when Link loses all the hearts in his health meter & completely replenishes his health. Only one Secret Medicine can be held at a given time, so if Link already has one & gets another from a treasure chest, he will still only have 1 Secret Medicine in his inventory. It initially costs 28 Rupees if Link buys it from Crazy Tracy & costs 42 Rupees every subsequent time he goes back to buy more after using it up.