Bloodletting: Why doctors used to bleed their patients for health

Bloodletting: Why doctors used to bleed their patients for health

Written by Maria Cohut, Ph.D. on November 16, 2020

Bloodletting — the practice of withdrawing blood from a person’s veins for therapeutic reasons — was common for thousands of years. In this Curiosities of Medical History feature, we look at the history of bloodletting and how it eventually fell out of favor with the medical community.

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Also known as phlebotomy — from the Greek words phlebos, meaning “vein,” and temnein, meaning “to cut” — bloodletting is a therapeutic practice that started in antiquity.

Today, however, the term phlebotomy refers to the drawing of blood for transfusions or blood tests.

Some sources suggest that the original practice of bloodletting is more than 3,000 years old and that the Ancient Egyptians, Greeks, and Romans — as well as many other ancient peoples — all used it for medical treatment.

But what is the origin of the notion of bleeding someone to help them get better?

The theory of the 4 humors

Hippocrates — an Ancient Greek physician who lived in the fifth century before the common era and was one of the most important figures in the history of medicine — practiced medicine according to the theory of the four humors, or “humoral theory.”

This theory posited that there were four key humors, or liquids, in the human body and that imbalances in these humors were responsible for many physical and mental illnesses.

According to the most influential version of this theory, these humors were: black bile, yellow bile, phlegm, and blood.

In the second century before the common era, Galen — a famous Roman physician who also subscribed to the humoral theory — promoted arteriotomy, a bloodletting method, as a means of reestablishing the balance of the four humors and treating a variety of symptoms.

According to Galen, a bloodletting incision into the veins behind the ears could treat vertigo and headaches, and letting blood flow out through an incision in the temporal arteries — the veins found on the temples — could treat eye conditions.

The principle behind bloodletting is to remove some blood in a controlled way so that the patient does not end up bleeding profusely.

However, as some of Galen’s contemporaries observed, the famed physician could sometimes get carried away when administering this treatment.

Prof. Susan Mattern — a historian based at the University of Georgia in Athens — emphasizes one such account in a paper in The Lancet:

“[Galen] was an adamant defender of bloodletting against those who doubted its efficacy. Galen’s methods could be very messy: he let so much blood from one patient that the other doctors in attendance joked about it, comparing the sick man to a butchered animal: ‘Man, you have slaughtered the fever.’”

Bloodletting continued to play a role in medicine throughout Medieval Europe, and it persisted as a common therapeutic method up until the 19th century, when it gradually started to fall out of fashion.

The instruments that physicians commonly used for bloodletting ranged from grotesque-looking scalpels to tools and methods that some alternative medicine practitioners still use today. They included:

  • fleams, which looked somewhat like Swiss knives, producing several kinds of blades
  • spring lancets with a single thin blade
  • terrifyingly named “sacrificators,” which had multiple blades
  • cups that the physician could place over the incision to collect the blood
  • leeches, which some people still use for therapeutic reasons today


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