How Blood Donations Deplete Iron

blood and iron: how to optimize iron levels

A reader asked me a question that stumped me at first, so here’s the question, and my answer as to how blood donations deplete iron.

Q: “How is it possible to remove as much or more iron as ordinary food rapidly replaces? When I count the number of things whose contents individually constitute 100% of “RDA” or even higher, it strikes me that I’d have to just about bleed out every day to get rid of it all.

“Can you show an “iron balance”, with quantification showing elimination rates from various actions vs intake from various foods? That would be very helpful.”

A: Your question genuinely stumped me at first. I was wondering whether I had overlooked something. A blood donor loses about 250 mg of iron from his body iron stores with each donation, out of total body iron stores of 3 to 4 grams.

According to the NIH, average daily iron intake for an adult American man is about 20 mg, although not all of that is absorbed; as little as 10% is absorbed, or 2 mg, depending on lots of factors like food macro composition, alcohol intake, sugar consumption, use of supplements, etc. Meanwhile, the RDA is 8 mg (0.8 mg absorbed) so you see the problem: intake is 2.5 times the minimum necessary, which can ultimately lead to high body iron stores (high ferritin). 

At that rate of 2.5 mg a day absorbed, in 100 days, you’ve made up for the blood donation. But we do know that donating blood lowers iron levels quite well, so what gives?

The answer is that the 2 mg of iron absorbed daily is at a steady-state of body iron. Iron overload, unless extreme (genetic or some other reason) happens over years, slowly. Somewhat like if you gain 1.5 ounces of body weight a month, in 10 years you’re 10 lbs overweight.

Normal daily iron losses for an adult man are about 1 to 2 mg. So the iron you absorb daily just keeps even with losses. If you donate blood, and lose a lot more, absorption increases.

But if you lose blood via donation, phlebotomy, or being mauled by a bear, it will take longer than 100 days to make up for your lost iron at steady-state rates. If you lose a lot of blood, absorption really ramps up. 

In my book, I calculated that one annual blood donation is enough to keep ferritin in a low normal range, assuming low normal ferritin to start with. (With a high starting ferritin, a higher rate of donations is necessary to get down into the low normal range.) That’s ~250 mg a year of iron.

I calculated here that 75 mg of aspirin might get rid of 25 mg of iron daily, which exceeds daily intake.

I trust that all makes sense. The iron you ingest daily isn’t all added to body iron, because you lose a small amount daily, and when you donate blood, the same applies.

I discussed other aspects of blood donation, iron, and transfusion here.




Leave a Comment:

Matt says April 14, 2017

Hi Dennis,

Just listened to this and had to tell you, in case you haven’t heard it yet- the relationship between iron and aging came up in Dr. Rhonda Patrick’s latest interview. Jump up to 16 minutes:

    P. D. Mangan says April 15, 2017

    Thanks, Matt. I cited some of Gordon Lithgow’s research in my book. Also sent him a copy, although I never heard anything back.

      Bill says April 16, 2017

      PD I watched this video this morning. It is excellent. Gordon strikes me as a typical Scot. Reluctant to highlight his work unless he thought it through completely.

      I watched an interview with Dr Peter Attia as well with her. Again it was excelent though I did repeatedly think ‘let the man speak woman’ for both interviews. ! Hope I am allowed to say that here 🙂

        P. D. Mangan says April 16, 2017

        Bill – oh, yes, you can say that here. I’m part Scot myself, mother’s side were from Ayrshire. Maybe why I’m so modest, and cheap. (Not sure if I’m allowed to say that.)

          Bill says April 16, 2017

          Scots are renowned for being frugal and canny. But cheap ? Never ! 🙂

How Blood Donations Deplete Iron says April 15, 2017

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B1tman1ac says April 15, 2017

This is a good clinical trail that goes into some detail about iron & hemoglobin stores and replinishing them.

This article seems to indicte that healthy centenarian men have hemoglobin levels in the 12.4 g/dl range which is under the mandatory levels for being able to donate (13.0 g/dl).

I my self have donated whole blood over 30 times. Usual 2 to 5 times per year. My hemoglobin normally hovers around the normal range of13-15.5 g/dl and I get that checked every time I donate. However, my ferritin (iron) is always low when I get it checked during my yearly checkups, always 30-40 ng/ml. This even though I occasionally supplement with a vegatarian iron formula. However I’m also active and run a lot which bleeds iron from the system too and is another reason why I sometimes have to supplement to meet my needs. More so lately.

Oskar says April 16, 2017

Is that for real that only aspirin can remove 25mg of iron? So 10 day fast with little bit of aspirin would reduce the iron burden as much as donating blood?

    P. D. Mangan says April 16, 2017

    Oskar – that calculation is highly theoretical. In reality, aspirin won’t chelate 1 to 1 with every iron atom in your body, most of which is protein bound and not available for chelation.

Joshua says April 17, 2017

The paper about aspirin maybe being an actual iron chelator is quite interesting. Nice work, PD. It makes me kind of want to start a daily aspirin regime. Though since I’m only 36, I think the risk/benefit analysis probably doesn’t yet work in my favor. (I’d be worried about it impairing adaptations to strength training as well.) But when I hit 50 or so, this might be another reason to start trying a daily aspirin, methinks.

Ted says April 18, 2017

PD, do you have any info on links between donation & albumin, or iron and albumin levels?

    P. D. Mangan says April 18, 2017

    Albumin is sensitive to protein intake and malnutrition, the biggest factors as far as I know. In theory, lots of plasma or platelet donations, say weekly, could decrease albumin, but it’s unlikely to be a factor in whole blood or red cell donations. Iron doesn’t affect albumin levels, but may cause albumin to become oxidized.

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