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Scientific Name(s): Hirudo medicinalis L. Phylum: Annelida.
Common Name(s): Fresh water leech, Medicinal leech

Medically reviewed by Last updated on Apr 26, 2021.

Clinical Overview


Leeches have been used for bloodletting, wound healing, and stimulating blood flow at postsurgical sites. Use in osteoarthritis is being investigated, but there is a lack of clinical information to make recommendations.


Consult existing guidelines for the use of leeches.


Arterial insufficiency, previous exposure to leeches (risk of allergic reaction), immunosuppression (risk of infection), patient refusal to accept possible subsequent blood transfusions, and unstable medical conditions have been described as contraindications for extensive leech therapy.


Information regarding safety in pregnancy and lactation is lacking. Avoid use because of risk of infection and anemia.


None well documented.

Adverse Reactions

Extensive blood loss. Allergic reactions and infections may develop.


No data.


There are more than 700 species of leeches, all of which are carnivorous.1 The leech is an hermaphrodite, containing both male and female sexual organs, but is not self-fertile.

The use of medicinal leeches (H. medicinalis) is preferred because of their ability to bite deeply and cause prolonged bleeding even after they are detached. H. medicinalis can reach up to 12 cm long, but is generally smaller, weighing 1 to 1.5 g before feeding. H. medicinalis has both anterior and posterior suckers, with the head located at the narrow tapered end. The anterior sucker has 3 jaws, each with 60 to 100 teeth for biting. The posterior sucker is used for attachment and crawling.1

Leeches obtained from commercial breeders are easily maintained in a chlorine-free salt solution at 10° to 20°C. Under such conditions, leeches can survive for up to 18 months.


The medicinal use of leeches dates back to ancient Egyptians around 1300 BC; the Greek physician Galen (130 to 201 AD) commonly used leeches for bloodletting. The 19th century heralded the widespread use of leeches for bloodletting—leading to a leech shortage from 1825 to 1850 in France requiring the importation of leeches from America.1, 2, 3, 4, 5, 6 By the end of the 19th century, the medicinal use of leeches had lost popularity due to adoption of the modern concepts of pathology and microbiology.1


Different species of leeches secrete varying compounds with differing hematological actions.7, 8

Following attachment, H. medicinalis secretes hirudin, a selective thrombin inhibitor, which enhances bleeding and prevents coagulation.1, 9, 10 Hirudin was first described more than a century ago and characterized as a 65-amino acid peptide with antithrombokinase activity.1 Early therapeutic studies of hirudin were limited by low natural yield, but the compound has recently been produced in larger quantities by recombinant gene techniques.11, 12 Recombinant hirudin binds avidly to thrombin, thus low doses inhibit venous thrombosis in animals. Extracts from leeches have been marketed in creams for topical application. In addition to hirudin, leeches secrete hirustasin, which selectively inhibits tissue kallikreins; antistasin and ghilanten, which inhibit Factor Xa; calin, apyrase, and saratin, which inhibit platelet aggregation; a histamine-like compound, which causes vasodilation; hyaluronidase and collagenase, which increase permeability; and bdellin and eglin, which are proteinase inhibitors.1, 10, 13, 14

There is conflicting evidence as to whether an anesthetic is secreted in H. medicinalis.4, 15, 16 Theromyzon is widely distributed in the tissue of the leech Theromyzon tessulatum and has angiotensin-converting, enzyme-like properties8 and peptides with antimicrobial properties have been identified.17

Undefined anti-inflammatory substances in the saliva of medicinal leeches have been reported.18, 19

Uses and Pharmacology

Ischemic tissue

Medicinal leeches are used to stimulate the flow of blood at postoperative surgical sites.2, 15, 16

After attaching to the site, leeches secrete compounds, especially hirudin, that reduce blood viscosity. They provide the drainage needed to permit decongestion and to preserve tissue viability until normal venous flow is established.16, 20

Reviews of the use of 'hirudotherapy' in localized venous congestion or hematoma have been published; most commonly, only case reports exist in the literature.18, 21, 22

Other uses

Based on reported anti-inflammatory substances in the saliva of medicinal leeches, a number of clinical studies have evaluated the role of leeches in osteoarthritis.18, 19 Blinding of participants is problematic in such studies and comparators have used transcutaneous electrical nerve stimulation (TENS)23 and topical diclofenac.24 A meta-analysis of clinical studies (n=4) reported moderate to strong evidence for pain reduction, functional impairment, and joint stiffness following leech therapy.19


Institutional guidelines may exist for the use of leeches. Leeches are applied from 2 to 4 times a day for up to a week. Feeding is complete in about 20 minutes, at which time the leech drops off. Removal of the leech may be hastened by applying solutions of salt, vinegar, a flame, or a local anesthetic. Leeches should not be forcibly removed. Bleeding from the attachment site usually continues for several hours. Reuse of leeches is discouraged to minimize the development of cross-infection.1, 20, 25, 26

Pregnancy / Lactation

Information regarding safety in pregnancy and lactation is lacking. Avoid use due to risk of infection and anemia.


None well documented. Closely monitor conditions requiring concomitant anticoagulant therapy.

One study found no changes in ipsilateral activated partial thromboplastin or prothrombin times when leeches were applied to an intact hand. This suggests that systemic or local anticoagulation is not likely to occur and that the risk of interference with other therapies may be small.27

Adverse Reactions

Arterial insufficiency, previous exposure to leeches (risk of allergic reaction), immunosuppression (risk of infection), patient refusal to accept possible subsequent blood transfusions, and unstable medical conditions have been described as contraindications for extensive leech therapy.9

Blood loss

Leeches may consume up to 50 mL blood per application, and their secretions during a single feed can prevent coagulation (in vitro) of up to 100 mL human blood. Passive bleeding after detachment can continue up to 72 hours but most commonly continues for about 5 hours. Blood loss may occur, sometimes requiring transfusions.18, 28


H. medicinalis should be considered a possible vector of infectious diseases. The incidence of infection consequent to leech therapy ranges from 2% to 20%.21, 22

The gram-negative Aeromonas hydrophilia is the predominant microbial species found in leeches.1, 9, 29, 30 Serratia, Klebsiella, and Pseudomonas have also been isolated10, 31, 32, 33, 34 and patients should receive appropriate prophylactic antibiotic therapy. Older studies suggested possible transmission of HIV and hepatitis, but this is less likely with the use of farmed leeches.22, 35 Reuse of leeches is not recommended due to concerns of disease transmission.4


Local allergic reactions and anaphylaxis have been reported.36 Leeches found in the nose, throat, and the GI tract have caused complications.37, 38, 39, 40


No data.


1. Whitaker IS, Cheung CK, Chahal CA, Karoo RO, Gulati A, Foo IT. By what mechanism do leeches help to salvage ischaemic tissues? A review. Br J Oral Maxillofac Surg. 2005;43(2):155-160.15749217
2. Hayden RE, Phillips JG, McLear PW. Leeches. Objective monitoring of altered perfusion in congested flaps. Arch Otolaryngol Head Neck Surg. 1988;114(12):1395-1399.3190866
3. Rao J, Whitaker IS. Use of Hirudo medicinalis by maxillofacial surgical units in the United Kingdom: current views and practice. Br J Oral Maxillofac Surg. 2003;41(1):54-55.
4. Whitaker IS, Izadi D, Oliver DW, Monteath G, Butler PE. Hirudo medicinalis and the plastic surgeon. Br J Plast Surg. 2004;57(4):348-353.15145739
5. Ventura HO, Mehra MR. Bloodletting as a cure for dropsy: heart failure down the ages. J Card Fail. 2005;11(4):247-252.15880332
6. Hodgson D. Of gods and leeches: treatment of priapism in the nineteenth century. J R Soc Med. 2003;96(11):562-565.14594972
7. Ledizet M, Harrison LM, Koskia RA, Cappello M. Discovery and pre-clinical development of antithrombotics from hematophagous invertebrates. Curr Med Chem Cardiovasc Hematol Agents. 2005;3(1):1-10.
8. Rivière G, Michaud A, Deloffre L, et al. Characterization of the first non-insect invertebrate functional angiotensin-converting enzyme (ACE): leech TtACE resembles the N-domain of mammalian ACE. Biochem J. 2004;382(pt 2):565-573.15175004
9. Chepeha DB, Nussenbaum B, Bradford CR, Teknos TN. Leech therapy for patients with surgically unsalvageable venous obstruction after revascularized free tissue transfer. Arch Otolaryngol Head Neck Surg. 2002;128(8):960-965.12162779
10. Dippenaar R, Smith J, Goussard P, Walters E. Meningococcal purpura fulminans treated with medicinal leeches. Pediatr Crit Care Med. 2006;7(5):476-478.16878049
11. Wallis RB. Hirudins and the role of thrombin: lessons from leeches. Trends in Pharmacol Sci. 1988;9(12):425-427.3078081
12. Hand R, et al. A review of the pharmacology, clinical applications, and toxicology of hirudin and hirulog. Transgenica: J Clin Biotechnol. 1994;1:1.8172225
13. Deckmyn H, Stassen JM, Vreys I, Van Houtte E, Sawyer RT, Vermylen J. Calin from Hirudo medicinalis, an inhibitor of platelet adhesion to collagen, prevents platelet-rich thrombosis in hamsters. Blood. 1995;85(3):712-719.7833475
14. Harsfalvi J, Stassen JM, Hoylaerts MF, et al. Calin from Hirudo medicinalis, an inhibitor of von Willebrand factor binding to collagen under static and flow conditions. Blood. 1995;85(3):705-711.7833474
15. Baskova IP, Khalil S, Nartikova VF, Paskhina TS. Inhibition of plasma kallikrein, kininase and kinin-like activities of preparations from the medicinal leech. Thrombosis Research. 1992;67(6):721-730.1440537
16. Rados C. Beyond bloodletting: FDA gives leeches a medical makeover. FDA Consum. 2004;38(5):9.15595141
17. Salzet M. Neuropeptide-derived antimicrobial peptides from invertebrates for biomedical applications. Curr Med Chem. 2005;12(26):3055-3061.16375700
18. Porshinsky BS, Saha S, Grossman MD, Beery Ii PR, Stawicki SP. Clinical uses of the medicinal leech: a practical review. J Postgrad Med. 2011;57(1):65-71.21206115
19. Lauche R, Cramer H, Langhorst J, Dobos G. A systematic review and meta-analysis of medical leech therapy for osteoarthritis of the knee. Clin J Pain. 2014;30(1):63-72.23446069
20. Abrutyn E. Hospital-associated infection from leeches. Ann Intern Med. 1988;109(5):356-358.3044210
21. Elyassi AR, Terres J, Rowshan HH. Medicinal leech therapy on head and neck patients: a review of literature and proposed protocol. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;116(3):e167-e172.22819462
22. O'Dempsey T. Leeches--the good, the bad and the wiggly. Paediatr Int Child Health. 2012;32(suppl 2):S16-S20.23394754
23. Stange R, Moser C, Hopfenmueller W, et al. Randomised controlled trial with medical leeches for osteoarthritis of the knee. Complement Ther Med. 2012;20(1-2):1-7.22305242
24. Michalsen A, Klotz S, Lüdtke R, Moebus S, Spahn G, Dobos GJ. Effectiveness of leech therapy in osteoarthritis of the knee: a randomized, controlled trial. Ann Intern Med. 2003;139(9):724-730.14597456
25. Adams SL. The emergency management of a medicinal leech bite. Ann Emerg Med. 1989;18(3):316-319.2923340
26. Rao P, Bailie FB, Bailey BN. Leechmania in microsurgery. Practitioner. 1985;229(1408):901-905.4059170
27. Blackshear JL, Ebener MK. Leeching, hirudin, and coagulation tests. Ann Intern Med. 1994;121(2):151-152.8017735
28. Ikizceli I, Avsarogullari L, Sözüer E, Yürümez Y, Akdur O. Bleeding due to a medicinal leech bite. Emerg Med J. 2005;22(6):458-460.15911965
29. Ardehali B, Hand K, Nduka C, Holmes A, Wood S. Delayed leech-borne infection with Aeromonas hydrophilia in escharotic flap wound. J Plast Reconstr Aesthet Surg. 2006;59(1):94-95.16482796
30. Steer A, Daley AJ, Curtis N. Suppurative sequelae of symbiosis. Lancet. 2005;365(9454):188.15639303
31. Dickson WA, Boothman P, Hare K. An unusual source of hospital wound infection. Brit Med J. 1984;289(6465):1727-1728.6440623
32. Kourt B, Segars LW, Davis TW. When the prescription says "leeches." Am J Hosp Pharm. 1994;51(17):2113-2114, 2116.7985685
33. Bickel KD, Lineaweaver WC, Follansbee S, Feibel R, Jackson R, Buncke HJ. Intestinal flora of the medicinal leech Hirudinaria manillensis. J Reconstr Microsurg. 1994;10(2):83-85.8182569
34. Wilken GB, Appleton CC. Bacteriological investigation of the occurrence and antibiotic sensitivities of the gut-flora of the potential southern African medicinal leech, Asiaticobdella buntonensis (Hirudinidae). J Hosp Infect. 1993;23(3):223-228.8099096
35. Nehili M, Ilk C, Mehlhorn H, Ruhnau K, Dick W, Njayou M. Experiments on the possible role of leeches as vectors of animal and human pathogens: a light and electron microscopy study. Parasitol Res. 1994;80(4):277-290.8073013
36. Tseng CC, Ho CY. Removal of a nasal leech: a safe and effective method. Otolaryngol Head Neck Surg. 2005;132(5):814-815.15886644
37. Bergua A, Vizmanos F, Monzón FJ, Blasco RM. Unavoidable epistaxis in the nasal infection of leeches [in Spanish]. Acta Otorrinolaringol Esp. 1993;44(5):391-393.8129977
38. Uygur K, Yasan H, Yavuz L, Dogru H. Removal of a laryngeal leech: A safe and effective method. Am J Otolaryngol. 2003;24(5):338-340.13130448
39. Kuehnemund M, Bootz F. Rare living hypopharyngeal foreign body. Head Neck. 2006; 28(11):1046-1048.16933314
40. Krüger C, Malleyeck I, Olsen OH. Aquatic leech infestation: a rare cause of severe anaemia in an adolescent Tanzanian girl. Eur J Pediatr. 2004;163(6):297-299.15346909


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