Have you ever wondered why the main blood test for iron levels doesn’t test iron? And are you now wondering what inflammation has to do with it? If so, we are here to make sense of those medical tests, connections and conclusions.
Anemia means that your blood has low levels of one of its normal constituents. It's a word most commonly used to refer to iron deficiency anemia. Other anemias are described by other terms, such as pernicious anemia (vitamin B 12 deficiency), and aplastic anemia (low red blood cell production in bone marrow). This health post is about iron deficiency anemia, because this is the most common type, especially in women of menstruating age.
Iron is a mineral your body uses in a number of ways. It is best known as the atom in the middle of the hemoglobin molecules in your red blood cells. There it carries the oxygen molecules it has picked up from your lungs, and disperses them to all of your tissues, because every cell of your body needs oxygen. If your cells aren’t being supplied with enough oxygen they can’t make as much energy, which is one of the reasons anemia leaves people feeling tired and weak.
Iron is also an essential co-factor for creating energy in your mitochondria: so low iron levels have a double impact on reducing your ability to produce energy.
We don’t absorb iron very well. Because we have no biochemical pathways to excrete iron, and too much iron can become toxic, it is important not to absorb too much. Low absorption of iron is a protective mechanism! However this mechanism is not helpful for women in their menstruating and child-bearing years, if they lose significant amounts of blood each month. And this is just at the time of life when they need energy to look after their kids as well as themselves!
This is also why iron deficiency anemia in someone who is not menstruating needs to be checked out. They need to find out whether they aren’t absorbing enough (for example due to celiac disease) or if they are losing it too fast (for example due to bleeding in the gut).
An easy self-check for significant anemia is to look for a pale inner lower eyelid. Just pull the lid down when looking in the mirror. If it isn’t getting enough circulating oxygen, neither is the rest of your body! But usually iron levels have to be pretty low to cause that. Blood tests can give us a more precise assessment.
Ferritin is the molecule that enables iron to be stored in your liver.
This stored iron is ready to be used to make hemoglobin, as and when you need it. It is more like the food in your pantry, waiting to be used to make energy, rather than the food in your tummy, which is in the process of making energy right now.
If you have good amounts of iron stores, your ferritin count will be high. If your ferritin is low, your iron stores are low, and your diagnosis is iron deficiency anemia. This is why ferritin is the marker you will see most often on blood tests, because your doctor is usually checking for iron deficiency.
But ferritin is also a marker of inflammation, because it can leak out of damaged inflamed cells. So if your ferritin is high, it doesn’t necessarily follow that your iron stores are high. It may well be that iron stores are good, but it could also mean inflammation is present. If your ferritin is very high (over 200 ug/L), there is significant inflammation, so more testing is definitely needed. However if ferritin is in the high-OK range, does it indicate good iron storage, or some inflammation, or a bit of both? Without further testing it is hard to tell.
How can we work with this?
We can test iron levels as well as ferritin levels.
Because iron levels check what’s circulating in the blood, and ferritin reflects your stores and/or inflammation, testing both gives a better picture of your overall iron status.
In addition, if ferritin is high, but iron is low, we know that there is inflammation. We still don’t know the source of that inflammation, but at least we know we should look for it.
Ferritin isn’t the only marker of inflammation, so if it is low, we can’t conclude that you don’t have inflammation. Given the amount of inflammation associated with Long Covid and other conditions, it isn’t surprising that we are seeing some people whose ferritin is higher than matches their iron levels. One study actually suggested ferritin could be used as a marker for testing for Covid 19. In an ever-more inflamed world, it has become more important to understand these complexities of how iron works in our bodies.
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