Iron Deficiency Causes: where it really comes from

Iron deficiency arises along three main routes: the body loses iron (blood loss), it needs more than usual, or it absorbs too little. Often a silent inflammation is added that holds back the available iron. In my view, clarifying the cause is part of the actual treatment, not just topping up.

Many people with iron deficiency know the feeling of having taken iron several times and still standing at the same point a few months later. That is rarely bad luck. Usually a cause keeps running in the background that was never named. That is exactly the point here: not symptoms, but the question of where the deficiency comes from.

Route 1: Blood loss, the most common reason of all

Every milliliter of blood carries iron with it. Hemoglobin, the red blood pigment, is largely iron. That is why ongoing or recurring blood loss is the most common cause of iron deficiency worldwide. The decisive question is only: from where?

Menstruation: the silent steady loss

A normal period loses about 15 to 20 milligrams of iron per cycle. A heavy or long bleed can cost two to three times that. Over months and years this adds up. In women of childbearing age, menstruation is by far the most common trigger of iron deficiency. If the period is very heavy, lasts many days, or comes with clots, a targeted look at the iron stores is worthwhile. More on this in the dedicated post on iron deficiency in women and heavy periods.

The gastrointestinal tract: the hidden source

A small, unnoticed bleed in the digestive tract can be enough over a long time to empty the stores, without ever seeing visible blood. Possible reasons are stomach ulcers, inflamed mucosa, hemorrhoids, vascular changes, or, more rarely, more serious findings. That is exactly why an important rule applies.

Frequent blood donation

Donating blood is a valuable act. At the same time, each whole-blood donation removes a substantial amount of iron from the body, roughly in the order of 200 to 250 milligrams. Whoever donates often, especially menstruating women, can slip unnoticed into a deficiency.

Route 2: Increased demand, when the body suddenly needs more

Sometimes the intake is unchanged, but the demand rises. Then the old amount is no longer enough, and the stores slowly fall.

Sport: more than just sweating

In runners and other endurance athletes, iron can become scarce through several routes: tiny blood losses in the gastrointestinal tract under load, through sweat, through the mechanical bursting of red blood cells in the soles of the feet, and through a short-term rise of hepcidin after intense exertion. More on this in the planned post on iron deficiency in athletes and runners.

Route 3: Impaired absorption, eating enough is not always enough

Some people objectively eat enough iron and still have a deficiency. The reason then lies in the gut: the iron does not arrive. This is one of the most frequently overlooked causes.

Plant iron is absorbed less well

Iron from animal sources, so-called heme iron, is absorbed much better than the non-heme iron from plants. Plant compounds such as phytates from whole grains and legumes or polyphenols from coffee and tea can additionally inhibit absorption. Vegetarian and vegan people therefore need more attention for their iron supply, not because their diet is poor, but because absorption is mathematically lower. In detail in the post on iron deficiency on a vegan and vegetarian diet.

Stomach acid, acid blockers and the underrated stomach

For iron to be absorbed in the small intestine, stomach acid helps bring it into a more available form. When the acid is missing, absorption suffers. This affects people with age-related declining acid production, with chronic gastritis, and also people who take acid blockers, so-called proton pump inhibitors, over the long term.

Celiac disease and chronic bowel inflammation

In celiac disease, an intolerance to gluten, the small-intestine lining is damaged, exactly where iron is absorbed. A stubborn iron deficiency can be the first and sometimes only sign, long before anyone thinks of abdominal complaints.

Chronic inflammatory bowel diseases such as Crohn's disease or ulcerative colitis also often lead to iron deficiency, partly through blood loss, partly through impaired absorption, partly through the inflammation itself.

Helicobacter pylori: the invisible player

The stomach bacterium Helicobacter pylori can chronically inflame the gastric mucosa and so disturb iron absorption. In some cases a stubborn iron shortage can only be managed again once the bacterium has been treated.

The special case: hepcidin and the silent inflammation

There is a situation in which there is enough iron in the body, yet too little usable iron arrives in circulation. Responsible is a hormone called hepcidin. Picture it as a doorkeeper. When hepcidin is high, the door closes: absorption in the gut drops, and the stored iron is held back.

Hepcidin rises above all in inflammation. A chronic, often barely noticeable inflammation, for example with overweight, autoimmune processes, an ongoing infection, or bowel problems, can keep hepcidin elevated. The result is a functional iron deficiency: complaints despite existing stores.

Why "just topping up" often falls short

Now that you have the three routes in mind, it becomes clear why pure topping up often does not suffice. As long as the source keeps running, the store falls again after topping up. This applies to the heavy period just as to impaired absorption or ongoing inflammation.

A good workup therefore always asks both: how deep is the store, and why is it empty? In integrative medicine we like to see iron deficiency in context: with nutrition, with the gut, with hormonal patterns, with the load of everyday life. That is no truth above conventional diagnostics, but a second lens beside it.

And now you know why

If you have felt tired for a long time, have taken iron again and again, and still do not get anywhere, that rarely lies with you. It usually lies in the fact that a cause was never named. You may ask the question: where does this actually come from? That question is the beginning of a treatment that can do more than briefly fill the store.

Read on in the iron guide