Diamond (Dr. Mario World)
Diamonds are the premium currency in Dr. Mario World mainly used to summon new doctors, assistants, and single-use items. They can also be used to purchase more hearts if the player runs out, to give the player more capsules if they run out in a certain level, to give the player more time in challenge levels, or to start a level with a completely-filled skill meter. Another way to spend diamonds is through referrals (introduced in version 2.0.0), which cost 100 diamonds in exchange for that specific doctor.
Diamonds are usually purchased via real money, though there are some instances in which Diamonds may be collected for free during gameplay.