"Hirudo medicinalis, the medicinal leech: popular among Muggle healers (who believe that the blood-sucking creatures are able to treat illnesses) and useful to wizards in potion-making."
Zygmunt Budge, Book of Potions.[src]

Leeches are small slug-like invertebrates that live in water. They feed on human blood and/or that of other small invertebrates.[1] Leech spit contains an anticoagulant (a substance that prevents blood clotting), allowing them to feed for longer than blood would normally flow.[2]

In potions


A jar of leeches

The Hirudo medicinalis species (vulgarly known as the medicinal leech) are used in Potion-making. To make the Polyjuice Potion, four unsucculated leeches are required.[3][4] Also, a dash of leech juice is a required ingredient in the making of the Shrinking Solution.[5] Flabberghasted leeches are also used in potion-making.

Behind the scenes

  • The use of leeches in the Polyjuice Potion was chosen by J. K. Rowling to represent "[sucking] the essence out of one and into the other".[6] Interestingly, the film prop used for Moste Potente Potions suggests that the leeches used have their suckers removed.
  • Zygmunt Budge uses the phrase "hearts' content" (rather than "heart's content") in regards to leeches in Wonderbook: Book of Potions, properly using plural possession as leeches have two hearts.


Notes and references

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