My Grandpa used leeches on his varicose veins back in the 1950’s and 60’s.
He kept them in a glass jar filled with water.
The removal of blood is still used to treat people with hemochromatosis - excess iron in the body. The goal is to induce a slight anemia to drain the excess iron from the tissues back into the circulation.
The practice of bloodletting for high blood pressure is fraught with danger to the patient. To be effective a quantity of blood would need to be removed to induce shock which opens up a whole new can of worms.
I remain unconvinced.