How do you heal in Pokemon Go?

Pokemon only restore health through the use of Potions of varying classes and Revives.

There is no mechanic for natural healing in the game yet.

Apparently evolving heals Pokemon. Powering up does not - though it does increase their current health by the same amount as their increase in max health.

Right now the only way to heal is to get potions however me and some friends just trained up a gym and a lot of my Pokemon got hurt so many that I ran out of potions and there is no way to buy potions at the moment except for picking them up at pokestops just keep that in mind before training a gym