The medicinal leech is a blood-feeding worm that has been used in medicine for thousands of years. Once common in European wetlands, it has declined because of over-collection and wetland loss.
Interesting facts
- Its bite leaves a Y-shaped mark made by three jaws lined with tiny teeth.
- Its saliva contains hirudin, a powerful anticoagulant, as well as an anaesthetic.
- A leech can drink several times its own weight in blood in one meal.
- It can survive for many months without feeding after a big meal.
- In the 1800s, France imported tens of millions of leeches a year for medicine.
- Over-collection for medicine made wild leeches rare in many countries.
Behaviour
Leeches swim with a graceful, wave-like motion and are attracted to movement and warmth in the water. They attach with suckers at each end.
Breeding and young
Leeches are hermaphrodites. After mating, they lay cocoons of eggs in damp soil near water.
Threats and conservation
Loss of wetlands, pollution and past over-collection.
Where to see it
- Protected ponds and marshes in Europe (rarely seen)
- Romney Marsh and the New Forest, England
- Licensed leech farms that supply hospitals
- Natural history museums
Status source: IUCN Red List. Profile last reviewed September 2026.
