Stomach-churning footage shows huge leeches used in blood-letting therapy in Bangkok, Thailand.

The unusual treatment called 'hirudotherapy' uses medical leeches to suck a small amount of blood from the patient's body. They attach to a patient's back and sink their fangs into the skin.

Some are up to six inches long and move with a gruesome slug-like motion.

At the Baan Khun Suk clinic in the Thai capital, each session lasts between 45 minutes to an hour, with a different set of leeches used per customer, staff said.

The doctor said: ‘Every patient gets fresh leeches for the treatment. The therapy improves blood circulation, reduces swelling and also offers pain relief for the patients.

'It might look scary at first, but the treatment is not painful at all. It feels like an ant bite. Many of our patients feel instant pain relief after each session.'

There have been several studies and case reports that suggest hirudotherapy, a form of blood letting, can be an effective treatment
for certain conditions. It is gender neutral and popular among both men and women.

Conditions that hirudotherapy can treat include venous congestion, pain management, cardiovascular disease and skin conditions.

Hirudotherapy is a medical treatment that should only be performed by a qualified healthcare professional and should not be attempted at home.