"Just a week ago I was in Austria doing a cleanse and part of the treatment was leech therapy," Moore said on "Late Show with David Letterman" Monday night.
"It detoxifies your blood and they have a little enzyme that when they're biting down on you gets released into your blood," the actress added. "Generally you bleed for quite a bit and it detoxifies your blood."
Moore said that the treatment is uncomfortable, but a little Lamaze breathing helps her get past the pain.
"They start in a spot for me that is a horrible spot: my belly button," she said. "It crawls in and you feel it bite down on you ... and then you just watch it swell up and get fatter and fatter and then when it's super drunk on your blood it just kinda rolls over like it's stumbling out of a bar."
"Leeches don't like hair," she warned. "So if you're hairy be prepared to do a little shaving or waxing. They much prefer Brazilian."
Although it sounds bizarre, leeches do have a place in modern medicine.
In 2004, the Food and Drug Administration (FDA) cleared the commercial marketing of leeches for medicinal purposes for the first time when it granted approval to French company Ricarimpex SAS.
According to the FDA, leeches can help heal skin grafts by removing blood pooled under the graft and restore blood circulation in blocked veins by removing pooled blood.
Leeches have been used as an alternative treatment to blood-letting and amputation for several thousand years. They reached their height of medicinal use in the mid- 1800's. Today they are used in medicine throughout the world as tools in skin grafts and reattachment surgery.
Moore is currently promoting her new movie, "Flawless," which co-stars Michael Caine.