It used to be a common general medical procedure - if the patient was sick, you cut open a vein and drained off a pint or so of blood. If the patient didn’t get better the first time, repeat until either good health or death resulted.
Nowadays, the consensus is that your blood should remain inside your body. But was bleeding ever a good idea? Were there any common health problems that would benefit from a moderate amount of blood loss?
I’m sure our medical staff will be along shortly with more.
The Wikipedia page on bloodletting has some general background and info; suggests that the beneficial effect may be placebo, and perhaps some use in hypertension and few odd complaints that require the red cells to be reduced… but on the whole, quackery.
Oh yeah… IANADr… nor do I play one on television. 
Leeches, once used widely, then scorned as real medicine came about, are now back again. They help restore blood flow to reattached limps and so forth. Maggots are also used to eat away large areas of dead tissue. The maggots will only eat the dead tissue, so there’s less risk than surgery, where live tissue might be taken as well.
I have read stories of surgeons re-attaching severed fingers and toes. According to the stories I read, it is much easier to re-establish blood flow in the arteries, than in the veins. Blood flows quickly into the finger, but slowly out of it. This causes swelling in the finger, and stress on the sutures. Supposedly, the surgeons were experimenting with leeches to remove the excess blood. I have no idea if the experiments were successful or not.
Darn, I hate it when my limp re-attaches… 
Polycythemia can also be an indication for therapeutic phlebotomy, as it is now called.
But as per the OP, there aren’t any common conditions where it is recommended.
We don’t call it therapeutic phlebotomy Hirundo82 . We call it venesection (as opposed to venepucture, which is your basic blood draw).
One of the last-ditch old school treatments for fluid overload and pulmonary oedema, in the context of heart failure, is to venesect a patient and remove about a unit of blood. This is based on the theory that the blood letting reduces the circulating volume and some of the unwanted excess fluid in the lungs will move back into the blood vessels, thereby reducing the pulmonary oedema.
I’ve seen it done recently, as an adjunct to diuretics, CPAP and other conventional therapies. It worked. Our patient went from “might not live through the night” to going back home within 7 days.
Venesection is standard treatment for Haemochromatosis, as runner pat says. We have several patients who come in for fortnightly venesection to keep their iron stores within normal limits.
There is an anticoagulant, Hirulog, which is derived from leech venom. It is extrememly effective and is used when patients have an allergy to more conventional anticoagulant treatments like heparin. DVTs, PEs, some strokes and most heart attacks are now treated by systemic anticoagulation.
Medical maggots are fairly common place and are used for the treatment of leg ulcers and necrotic or sloughy non-healing wounds. They work well. It isn’t really true that they “eat” the dead tissue, the maggots secrete proteolytic enzymes that breakdown the damaged tissues and kill the bacteria in the wound. They go by the slightly more appealing name of “larval therapy”. LarvE is the brand i’m most familiar with and we tend to use the “teabag” style dressing rather than the free-range maggots.
If your patient happened to have haemochromatosis or congestive heart failure with pulmonary oedema, bloodletting could have been a good treatment, otherwise, not so much. Likewise, if they had a blood clot, leeches would have been ideal, otherwise, not a great plan. Maggots would have been OK in a nasty wound, but there is a risk that non-sterile maggots would have introduced more infection. Still, in the days before effective debridement surgery and antibiotics, I suppose you just had to take your chances.
<hurk>
Band name?
Take this with a grain of salt, but a historian I once read noted that it actually had a nice effect on feverish patients. If you take enough blood, their body temperature drops a little and they get tired and fall asleep. To a casual observer, it might seem like bleeding was a good tool in the case of fevers.
True, but they are not “back again”. The new surgical use issn’t what they used to use leeches for.
Wouldn’t blood-letting reduce blood pressure?
That’s what started me on this question. I have high blood pressure and was once told I couldn’t donate blood because it was too high. I figured that donating a pint would be a win-win situation - somebody else would get the blood and my blood pressure would temporarily drop back down to a better level. But I was told it doesn’t work like that.
There is a condition where iron builds up in the blood and causes liver damage. Not sure of the exact name exactly but part of the treatment for this is to remove blood.
An elevation in blood pressure is not usually due to too much circulating volume, but to dysregulation of your vascular muscle tone or other auto-regulatory dysfunctions. Your body will replace the volume of the blood you donate very quickly (within minutes) from your interstitial fluid although it will take weeks to replace the red blood cells.
That would be ‘hemochromatosis’ which has been mentioned several times above.
It is worth re-emphasizing one of the points that irishgirl made, i.e. that bleeding would work for pulmonary edema (congestive heart failure). In fact, given that rheumatic fever was likely quite common in the “old days” when bleeding was frequently employed, and given that pulmonary edema is a late complication of rheumatic fever, I’d bet that bleeding was often a rather succesful treatment.
Along these lines, although we don’t use bleeding to treat pulmonary edema anymore, we might still use tourniquets which are its equivalent. In other words, the tourniquets cause blood to be sequestered (trapped) in the limbs thereby removing it from the circulation (until the tourniquets are released). This helps people with pulmonary edema and can be used if you’ve nothing else to offer (e.g. camping in the middle of nowhere) or to buy some time while the more usual treatments kick in.
It surprised me to find that my pharmacy (where I worked) stocks leeches.