And he slowly lapped it up, gazing into her eyes...

October 2, 2008 7:50 AM

If a person were losing blood daily, just a little bit, how much would have to be lost daily for the person to feel it physically? How much would be lost for it to be dangerous? What supplements are useful in this situation?

[Please no "Go see a doctor" answers, this question is not about me]

Let's say we had a person who is somehow or the other leaking blood, for example through a wound that does not close, or because vampires are feeding on the person every night. This person is losing just a little blood every night, perhaps enough to fill 2-3 centimeters of a straw.

Would this have an effect on the well being of the person? Would the person crave a particular type of food? Is there a particular type of food the person should take? Vitamins? Fruits? Liver? Steak extra rare?

At what quantity of daily blood loss will it start getting dangerous for the person?

posted by ChabonJabon to health & fitness (20 comments total)

No, you dont crave anything. You feel sick and perhaps you die.

Symptoms of internal bleeding:

* Soft tissues, such as in the abdomen, are tender, swollen or hard. An enlarged, rigid abdomen, for example, is a good sign of internal bleeding.
* Anxiety or restlessness.
* Rapid, weak pulse.
* Rapid breathing, shortness of breath (with no other respiratory problems present).
* Skin that is cool, moist or looks pale, ashen or bluish.
* Nausea or vomiting. Vomiting blood.
* Bruising in the injured area (bruising may indicate deeper damage)
* Abdominal pain.
* Excessive thirst
* Decreased level of consciousness
* A severe headache.
posted by damn dirty ape at 8:00 AM on October 2, 2008

But wouldn't external bleeding have different symptoms & ramifications?
posted by dawson at 8:04 AM on October 2, 2008

I think you're looking for rates and rough guides, so here's some napkin math...

When you give blood, you lose a pint (about 500mls) of fluid.

Using these replacement times (I checked the Red Cross site and it seems to agree)....

It takes 24-48 hrs to replace the plasma (overall liquid volume);
It takes 3-4 weeks to replace all the "lost" red blood cells;
It takes 4-6 weeks to replace all the "lost" iron.

So if you're losing more than 500mls of blood per day or two, you're in trouble because you won't have enough plasma to circulate and that's a huge health risk. If you lose at a slower rate (500ml per month) you will be permanently and increasingly red blood-cell deficient, with all the health issues entails. And even at 500ml per two months or so, you'll be iron deficient, with the smaller health risks and cravings for iron-rich food that entails.

You can rejigger the loss rate to get the effect you want above.
posted by rokusan at 8:06 AM on October 2, 2008

Loss of blood is loss of blood. Although, the peas size amounts in the question probably wont produce many of these symptoms.
posted by damn dirty ape at 8:06 AM on October 2, 2008

So you're suggesting a loss of ~1-2ml a day? I think a person would be able to compensate for this for awhile, especially since if he or she *did* start to become anemic, the body would sense it and release erythropoetin, a chemical that stimulates the production of red blood cells.

(I couldn't tell you how many RBCs an average person produces per day, but the average person of "average" size has about 5L of blood.)

If they became anemic, they might develop pica.

"Dangerous" depends on the person. A young, healthy person can probably technically feel fine with a low blood count that would cause symptoms of chest pain, shortness of breath, or other problems for an older person with coronary artery disease. If your blood levels drop too low, it can cause ischemia of your heart and other vital organs.
posted by gramcracker at 8:08 AM on October 2, 2008

I would think that's for major internal bleeding, though, damn dirty ape. A small amount of blood loss isn't going to cause all those symptoms, if it causes any.

To throw a number out there, American blood banks generally allow you to donate a pint of blood every eight weeks; this is to allow the red blood cells to be replenished. (Plasma, the liquid part of the blood, is replenished relatively quickly.) If we assume that one could "divide this up" without any ill effects, this would correspond to losing about 8.5 ml of blood per day, or about half a cubic inch.
posted by Johnny Assay at 8:12 AM on October 2, 2008

Or, to think about it another way: an average adult has about 5 L of blood. You're proposing to take about 1-2 mL of that every day, or less than 0.05% of the total volume. It's hard to see how that would have any effect (assuming you could protect the "open sore" from infection, of course.)
posted by Johnny Assay at 8:16 AM on October 2, 2008

Hypothetical filter? Is there a particular reason that you're looking to find this out? At least tell us you're writing a book. The amount as small as you're referring to (2-3cm of a straw) isn't going to have any noticeable affect on the person you'll be biting. I've had regular nosebleeds (at elevation, during mountain climbs) where I've lost more than that on a daily basis and had no other symptoms.
posted by allkindsoftime at 8:17 AM on October 2, 2008

I had ulcer bleeding and my understanding is that it wasnt large amounts, but just enough to cause some of those symptoms. My point is that real life isnt like a bodice-ripper vampire novel. When you lose blood its pretty obvious and horrible. There's no cravings for red meat or thing coloreds red or any other cliche, although you might feel thirsty. You just feel sick and shitty and dont know why.
posted by damn dirty ape at 8:21 AM on October 2, 2008

I'd guess I lose about as much blood pricking my finger for glucose tests several times a day. Complete non-issue there.
posted by Rendus at 8:22 AM on October 2, 2008

People can function on very low hemagoblin value very well and not even know it. They just feel tired and listless. I have drawn blood on people with as low as 4.2 gm of hemagoblin and they were walking and talking. The average for a man is about 15 and 12 for women.
posted by bjgeiger at 8:22 AM on October 2, 2008

According to wikipedia an average human produces something like 2 millions red cells per second, that is about 172 billions a day, and at any moment you have about 2.5x10^13 (25,000 billions) of those.

The average concentration of red cells in blood is 5 billions per cubic centimeter, so if you're talking 2-3 cm of a straw, which I guess is no more than 1 cubic cm depending on the section of the straw, it's about 0.02% of the total red cell count, which I think is an absolutely negligible oscillation.
posted by _dario at 8:24 AM on October 2, 2008

When you give blood, you lose a pint (about 500mls) of fluid.
[...]
It takes 4-6 weeks to replace all the "lost" iron.

The amount of blood taken when giving blood usually doesn't cause someone to faint, but occasionally does. That's for someone weighing at least 110 lbs and generally healthy.

The 3cm-of-a-straw amount you mention is about 1ml. If it takes 6 weeks to replace the iron in 500ml of blood, then you could replace the iron in 1ml of blood in (6 weeks/500=) 2.02 hours; and you could lose (500/(6 weeks) * 1 day=) 11.9ml (a little over 2 teaspoons) every 24 hours and replace the iron OK.

Loss faster than that rate, but not faster than red blood cells etc get replaced, and you'd presumably get the symptoms of low iron which could be treated with iron supplements. Needless to say, if you're losing blood faster than that there may be other symptoms.
posted by Mike1024 at 8:36 AM on October 2, 2008

allkindsoftime and Solon and Thanks, I think the title of the question is a gentle hint; whether it's for research purposes or personal ones is another matter.

As for an answer, ChabonJabon, you might want to check out this resource: Blood: How Much is Too Much?. I apologize if I'm drawing the wrong conclusions, but either way the website seems to be a pretty good resources on matters of blood safety.
posted by suedehead at 9:36 AM on October 2, 2008

...pretty good resource...
posted by suedehead at 9:36 AM on October 2, 2008

My ex used to have nosebleeds constantly. He was completely fine, and lost more blood than 2-3 centimeters of a straw.
posted by sondrialiac at 9:54 AM on October 2, 2008

I can't claim any special knowledge, but I suspect that constant, very slow blood loss might be treated somewhat differently by the body than losing a pint at once, as in the donation scenario. Obviously, there is a level above which the body can't adapt, but I don't think you can extrapolate directly in a linear fashion from 500 ml donation once every 60 days to x ml every day.

As an example of differences in slow changes vs quick changes think about the effects of altitude. A process of slow acclimatization to altitude allows you live and work at an altitude that would cause serious problems if you went to that elevation quickly. And indeed altitude causes you to generate extra red blood cells -- other stresses on the system might do the same.
posted by Quinbus Flestrin at 10:09 AM on October 2, 2008

I am not a doctor, but personally have lost that amount or more blood on a near-daily basis for many years (due to a fissure, details intentionally spared). I've had it looked at dozens of times, by dozens of doctors, and none of them have ever found it worth doing anything about until/unless it gets worse. Really, it's more an annoyance than anything else.

I do make a point of iron-ing up just to be safe, but that's about it.
posted by Pufferish at 10:55 AM on October 2, 2008 [1 favorite has favorites]

Women regularly lose this amount of blood on a daily basis for the duration of a normal period, virtually all with no ill effects. Back in the day, I had Norplant and bled every single day for three years and was absolutely fine.

I'd worry about what's causing the bleed, but not the bleeding itself.
posted by DarlingBri at 7:47 PM on October 2, 2008

Back in the day, I had Norplant and bled every single day for three years and was absolutely fine.

On the other hand, a colleague of mine also had Norplant and after a couple of months of bleeding every day started fainting all over the place. Her diet wasn't that great and her job was quite physically demanding, both of which may have been contributing factors, but she was diagnosed with anaemia and in the end had to leave work. Various things she was recommended to eat included red grapes/grape juice, dark chocolate (both for iron), and orange juice or other foods containing vitamin C in order to help her body absorb iron from food.
posted by Lebannen at 10:21 AM on October 3, 2008