Medical leeches pierce a person's skin with their teeth and introduce anticoagulants through their saliva. The leeches are able to suck blood from the person being treated for 20 to 45 minutes at a time. This means a comparatively modest quantity of blood, about 15 millilitres for each leech.
There are various circumstances in that leech therapy can be applied. People who could profit from it include those facing the threat of limb amputation as a result of the side effects of diabetics, those who have been diagnosed with heart disease, and people having aesthetic operations where they are facing the danger of missing part of their soft tissue. It has also been suggested for the treatment of blood clots and varicose veins.
Individuals with anaemia, blood clotting problems or damaged vessels are not suitable for leech therapy. Also, children under the age of 18 and pregnant women are generally advised to avoid it.