You don't hear too much about bloodletting in modern-day America, but bloodletting has a long history to which blood was considered one of the four "humors", which also consisted of phlegm, yellow bile, and black bile and therefore the lancing of veins in one's body was performed or the usage of leeches were done to help balance out the four humors to which blood was considered to be a substance that must be "let out" because the prevailing belief at that time was that blood was stagnant within the body.
Bloodletting was a common practice for nearly 3000 years and was considered to be a necessary and absolutely vital step to bringing a patient back to good health, when such a patient was obviously suffering from some sort of illness or discomfort. So common of a procedure was bloodletting, that when George Washington was complaining of a throat infection, he had a massive amount of blood removed from this body within a very short period of time, which was probably and unfortunately the main cause of his death only a few hours later. That a man of Washington's stature and renown, the father of our country, would be treated in this manner is but a reflection of how mainstream bloodletting was back in its day.
Bloodletting eventually began to disappear out of favor within the last 100 years as medicine became more modern and more knowledgeable, to which the indiscriminate bleeding of patients was no longer considered to be in the patient's best interest. However, believe it or not, bloodletting has not completely disappeared within the medical annals of today. For instance, bloodletting with leeches is effectively used for certain microsurgical procedures because of the anticoagulant capabilities of leeches which are critical in preventing blood clots.
The donating of blood is considered to be a form of bloodletting which benefits the recipients of the blood but probably also benefits the giver of blood too. That is to say, the giving of blood will help to lower blood pressure which is a known benefit for most people because hypertension is debilitating. This implies that the voluntary giving of blood, or bloodletting, for those that suffer from hypertension and/or for those who are obese, is something that should be seriously considered. Another consideration, for modern-day bloodletting is that the giving of blood helps to dispose of excess iron within the blood for those that are predisposed to hemochromatosis.
In ancient times, bloodletting was used too often and too indiscriminately, with results that frequently were not beneficial or were chimerical for the patient. Today we are much wiser and more readily recognize that bloodletting does have its place in certain, specific circumstances and for particular patients. With so many pills, potions, and surgeries in our world today, those that suffer from hypertension and/or obesity may find that regular bloodletting allows them a path to better health and a more fulfilling life. These areas of bloodletting show much promise and are certainly worth our time and our consideration to explore and to test further.