MOSCOW — They are small as physician assistants go, about two inches long, and slithery. They wiggle about for a bit on Elena A. Kalinicheva’s back before getting down to what they do best: sucking blood.

Leeches — yes, leeches — are still widely prescribed in Russian medicine, about 10 million of them every year, in many cases as a low-cost substitute for blood thinners like warfarin.

“When you do it the first time, you think, ‘My God, leeches!’” Mrs. Kalinicheva said. “But after you go through it, you understand there is nothing to worry about.”

In Russia, a medicinal leech costs less than $1, and a typical application requires three to seven of the ravenous little creatures. Leech treatments, available throughout the country, take 30 to 40 minutes, though the resulting wounds ooze blood for an additional six hours or so until the natural anticoagulant in leech venom wears off.