Leech (shui zhi)

What is leech? What is it used for?

The leech is a type of worm that belongs to the Hirudinidae class of worms. All leeches have 34 body segments, with a small mouth at one end and a large sucker at the other end. Leeches can range in size from only a few centimeters to more than 20 centimeters, and can stretch their bodies into a variety of lengths and widths.

The leech's mouth has three jaws, each with a row of sharp teeth, that form a y-shaped incision when attaching to an animal's flesh. The saliva of the leech contains substances that anesthetize the area of the wound, dilate the blood vessels and prevent the blood from coagulating. The anticoagulant is used medicinally, and is one of the reasons live leeches have been used by health care providers for centuries. Leeches are also killed for use in a variety of formulas.

Leeches are caught in early summer an autumn. They are killed by boiling, cut length-wise, dried in the sun, then cooked or ground into powder for use in herbal remedies.

In traditional Chinese medicine, leech has salty, bitter, neutral and slightly toxic properties, and is associated with the Liver and Bladder meridians. Its main functions are to invigorate the blood and remove blood stagnation, and to promote menstruation. Among the conditions that leech is used to treat are amenorrhea, abdominal pain and masses, chest pain and constipation. Leech is often combined with other herbs, such as rhubarb, peach seeds, and Chinese angelica.

How much leech should I take?

The amount of leech used in herbal formulas depends on the condition being treated and the form of leech being used. The typical dose of leech is between three and six grams, taken with water as part of a decoction; for powdered leech, the typical dose is 0.3-0.5 grams.

What forms of leech are available?

Leech is available in a variety of forms, including whole, dried and powdered. Live leeches are sometimes used to promote blood flow and remove stasis.

What can happen if I take too much leech? Are there any interactions I should be aware of? What precautions should I take?

Because leech has slightly toxic properties, it should never be used by women who are pregnant or breastfeeding. Live leeches should not be used by patients who have hemophilia or are on blood medications. As always, make sure to consult with a licensed health care provider before using leech or any other herbal remedy or dietary supplement.

References

• Bensky D, Gamble A. Chinese Herbal Medicine: Materia Medica. Brookline, MA: Redwing Book Co., 1986.
• Chen JK. Acupuncture and herbs in the treatment of neurodegenerative disorders: Alzheimer's disease, stroke, and Parkinson's disease. Medical Acupuncture Spring/Summer 1999;11(1).
• Flaws B. Chinese medicine & diabetic acromelic gangrene - Chinese medicine update. Townsend Letter for Doctors and Patients August-September 2003.
• LeBars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind randomized trial of an extract of ginkgo biloba for dementia. JAMA 1997;278:1327-1332.
• Yeung HC. Handbook of Chinese Herbs, revised edition. Brookline, MA: Redwing Book Co., 1983.