Leech Medic is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

When Leech Medic enters the battlefield, create a Leeches token card and put it into your hand. (Leeches is a sorcery from Homelands that reads, "Target player loses all poison counters. Leeches deals that much damage to that player.")