In women, low ferritin levels often receive an immediate explanation: “It’s your periods.” The equation seems obvious (losing blood, losing iron) to the point that the investigation sometimes stops before it even begins. However, menstruation does not explain why some women compensate for these losses without difficulty, nor why others remain deficient despite months of supplementation.
The state of the gastric terrain, often an underestimated entry point in a woman with iron deficiency, deserves particular attention.
The acidity of the stomach, the integrity of the mucosa, and the balance of the gastric microbiota determine whether the iron present in the diet will actually be transformed, absorbed, and used by the body.
Silent inflammation, chronic hypochlorhydria, or an unnoticed Helicobacter pylori infection can disrupt iron absorption long before the question of menstrual losses arises.
The gastric terrain then becomes the invisible lock that maintains the deficiency, even when intake seems adequate.
Poorly tolerated iron tablets, recurring nausea after each dose, constipation that sets in, and ferritin levels that stagnate despite months of supplementation: these are all signals that the problem is not solely in the losses but in the body’s ability to transform and capture what it is given.
This exploration does not replace medical follow-up. It opens a complementary perspective where the standard discourse sometimes stops at the prescription of tablets and the menstrual explanation. Understanding what happens in the stomach, the intestine, and the blood itself allows for different questions to be asked and more complete answers to be sought.
Heavy Periods Are Not Necessarily the Cause
Heavy periods (menorrhagia) can be a major driver of iron deficiency, especially when they persist over several years. But not all women with such menstruations develop a deficiency. Some go through years of regular cycles without ever lacking iron, while others see their ferritin levels drop despite moderate losses.
The difference lies as much in the body’s ability to compensate for these losses as in the volume of blood lost.
This ability depends on several stages: the transformation of iron in the stomach, its absorption in the intestine, its transport in the blood, and its storage in the cells.
When one of these stages falters, the deficiency sets in, even if dietary intake seems sufficient.
The mental fog that thickens, hands that remain cold even in summer, and a heart that beats faster with the slightest effort: the body tries to compensate for a lack that is not limited to a monthly loss.
Today, several mechanisms can disrupt iron uptake. The disruption can affect the transformation of iron in the stomach, its absorption in the intestine, its transport in the blood, or its storage in the cells.
Persistent inflammation can influence iron regulation. The terrain on which menstrual losses occur determines whether the body can compensate or not.
The State of the Gastric Terrain, an Overlooked Entry Point
Dietary iron comes in two forms: heme iron, found in meats, fish, and seafood, and non-heme iron, found in plants.
Heme iron is less dependent on gastric acidity, but it is not absorbed without any transformation.
Non-heme iron, primarily in ferric form (Fe3+), must be reduced to ferrous iron (Fe2+) to be better absorbed: this reduction begins in the stomach and continues in the duodenum, aided by hydrochloric acid and vitamin C present in the digestive lumen.
Insufficient gastric acidity can reduce the bioavailability of non-heme iron and contribute to a poor response to oral iron. However, it does not systematically prevent all absorption and affects heme iron less.
Hypochlorhydria, a reduced production of gastric acid, can result from chronic gastritis, inflammation of the gastric mucosa, or prolonged use of proton pump inhibitors (PPIs). These medications, prescribed to treat reflux or heartburn, significantly reduce gastric acid secretion.
Their long-term use can compromise the transformation of non-heme iron, regardless of what is on our plates.
Prescribed iron tablets are often poorly tolerated: nausea, constipation, digestive heaviness. Ferritin levels sometimes rise slightly, then stagnate.
Daily life remains marked by fatigue that does not relent, the impression that the body is not making use of what it is given.
This cause is often underestimated in a woman with iron deficiency. In many cases, the doctor prescribes iron tablets, the explanation stops at menstruation, and the investigation ends there. Meanwhile, the gastric terrain remains disturbed, and the deficiency persists.
H. pylori, the Often Overlooked Example
Helicobacter pylori is a bacterium that colonizes the stomach and affects nearly half of the world’s population. Generally acquired during childhood, it can remain silent for decades. In some people, it causes chronic gastritis and alters gastric acidity, two mechanisms that can disrupt iron absorption.
The link between H. pylori and iron deficiency is based on several mechanisms. The bacterium produces urease, which converts urea into ammonia and neutralizes the acid around it.
Its effect on overall acidity depends on the type and location of the gastritis: some infections reduce acidity while others increase it.
This alteration of the gastric environment can decrease the availability of ascorbic acid necessary for the reduction of non-heme iron.
H. pylori also uses iron for its own growth, thus competing with the body. Finally, the chronic gastritis it causes can stimulate the production of hepcidin and add an inflammatory component to the absorption defect.
These mechanisms can combine with menstrual losses and make replenishing reserves much more difficult.
Meta-analyses show that eradicating H. pylori can improve iron reserves in deficient patients, even in the absence of visible digestive bleeding. A documented case involved a menstruating woman whose deficiency resisted oral supplementation.
After the discovery and eradication of the infection, her ferritin levels normalized without additional iron intake.
In her case, menstruation contributed to the losses, but the main lock was in the stomach.
What Weakens the Gastric Terrain
A diet high in salt and processed foods but low in fiber and polyphenols can weaken the mucosa and impoverish the protective microbiota. It does not directly feed H. pylori, but it can create a more favorable gastric environment for its long-term establishment.
Conversely, fibers, polyphenols, omega-3s, and fermented foods help maintain the mucosa and its ecosystem.
Chronic stress can also disrupt digestion. Repeated activation of the sympathetic nervous system reduces the conditions favorable to digestive secretions. Eating quickly, under tension, or without real rest time can thus add an additional obstacle to already fragile absorption.
Finally, persistent inflammation, whatever its cause, can increase hepcidin and limit iron availability. This mechanism mainly concerns anemia of inflammation and mixed forms combining inflammation and true deficiency. It will be detailed in the section on hepcidin.
When Iron Is No Longer Available
Even when iron is present in the intestine, correctly reduced and ready to be absorbed, a second lock can block the passage: hepcidin. This hormone, produced mainly by the liver, regulates the passage of iron from intestinal cells to the blood.
It acts by blocking ferroportin, the transporter that allows iron to exit intestinal cells, macrophages, and liver cells to enter the bloodstream.
Two distinct scenarios exist.
In true iron deficiency, with or without anemia, reserves are depleted, ferritin is low, and hepcidin generally decreases. When hemoglobin also decreases, it is called iron deficiency anemia or IDA.
The body tries to release the little remaining iron.
In anemia of chronic disease (ACD), hepcidin remains elevated in response to inflammation, iron is sequestered in cells, and ferritin remains normal or high. These two situations can coexist: a woman can be truly deficient and also have an inflammatory component that complicates absorption. Fatigue persists, muscles remain weak, and daily life continues to weigh heavily.
Persistent inflammation, whatever its cause, can stimulate hepcidin, notably via the IL-6 pathway.
This mechanism is particularly important in anemia of inflammation and in mixed forms combining inflammation and true iron deficiency.
Certain metabolic contexts, such as obesity or insulin resistance, can contribute to this inflammation.
In a woman truly deficient in iron, the lack of iron itself can partially neutralize the inflammatory signal on hepcidin.
Inflammation does not mechanically explain a low ferritin typical of a true deficiency.
In anemia of chronic disease (ACD), the body enters a paradox: it lacks available iron for tissues, but it stores it in intestinal cells and macrophages, out of reach.
Oral iron supplementation does not resolve this blockage if the inflammatory terrain persists. The ingested iron remains sequestered at the intestinal level, and fatigue continues.
This scenario differs from a true deficiency, where reserves are depleted and ferritin is low.
Unabsorbed oral iron poses another problem. A sometimes significant fraction of iron in tablets is not absorbed: this depends on the dose, preparation, iron reserves, and inflammatory context.
Some of the iron we ingest is not absorbed by the body; it remains inside the intestine.
Researchers (Mahalhal and his team) studied this phenomenon in mice suffering from intestinal inflammation (colitis).
They observed that oral iron worsened this inflammation and altered the bacteria living in the intestine.
Vitamin C helps convert non-heme iron into a form that is easier to absorb, but its effect on clinical outcomes remains modest.
Nausea, constipation, and digestive heaviness after each tablet remain signals of poor digestive tolerance, to be taken seriously.
Intravenous iron infusion bypasses intestinal absorption and the lock that hepcidin imposes on intestinal cell ferroportin.
It is indicated in cases of oral intolerance, malabsorption, documented inefficacy of oral iron, inflammatory disease, or when rapid correction is necessary.
Modern formulations are iron-carbohydrate complexes: it is not a massive injection of free iron, even though a labile fraction and transient oxidative stress may exist.
Hepcidin also regulates the ferroportin of macrophages and the liver, the cells that store and redistribute iron already present in the body.
Even when iron arrives via infusion, a highly inflammatory terrain can still limit its actual use by tissues in the case of anemia of chronic disease (ACD).
Iron circulates, but it remains partially sequestered, poorly distributed.
Bypassing intestinal absorption does not address the terrain that caused the blockage in the first place. In a true deficiency, infusion can replenish reserves, but if an inflammatory component coexists, the scenario remains mixed.
Infusion also carries risks that should be known.
Certain formulations, notably ferric carboxymaltose, are associated with sometimes severe and prolonged hypophosphatemia, an imbalance affecting bones, muscles, and cellular energy.
A sudden increase in circulating iron can also, in certain contexts, promote the proliferation of pathogens that depend on it.
These effects do not occur systematically, but they exist and deserve to be weighed.
Meanwhile, fatigue persists, muscles remain weak, and daily life continues to weigh heavily.
Iron Does Not Work Alone: Copper, Zinc, and B Vitamins
Absorbing iron is not enough: it must also be transported, mobilized, and integrated into hemoglobin. Several micronutrients are involved in these different stages. A true iron deficiency is characterized by the depletion of reserves, but other deficiencies may coexist and explain why iron supplementation does not completely correct anemia or symptoms.
Copper also plays a key role in iron metabolism. Two enzymes that depend on it, one in the intestine and the other produced by the liver, convert iron into a form that the body can properly bind and transport. They also help release iron stored in the liver.
A lack of copper can therefore also disrupt iron circulation, cause anemia, sometimes accompanied by a decrease in white blood cells, and in prolonged cases, severe neurological disorders.
This interaction becomes important when someone takes zinc supplements over a long period.
At high doses or over time, zinc prompts intestinal cells to produce a protein that captures copper even better than it captures zinc itself.
Copper then remains trapped in these cells and is lost when they are shed and replaced, without ever reaching the circulation.
Prolonged zinc intake can thus gradually create a copper deficiency and indirectly disrupt iron metabolism.
This is not automatic: it all depends on the dose, duration, diet, and individual terrain.
But the balance between zinc and copper should be kept in mind whenever zinc is taken regularly.
B vitamins also play a role, but differently.
Vitamin B6 directly helps in the production of hemoglobin, but for this, the body must first convert it into its active form, called P5P.
Some people convert vitamin B6 less efficiently into its active form because of an overloaded liver or individual differences, and may therefore lack active B6 even when their diet provides enough.
This step can therefore also slow down hemoglobin production, even when iron is available.
Vitamins B9 and B12 do not act on iron absorption but are essential for the production of red blood cells themselves.
A lack of either causes a different type of anemia than iron deficiency, but both can coexist in the same person, complicating the interpretation of blood results.
Iron never works alone. When ferritin levels rise but fatigue does not resolve and hemoglobin does not meaningfully improve, the question is no longer simply, “Is there enough iron?” It also becomes, “Can the body transport and use it properly, or are other deficiencies involved?”
Adding supplements one by one, without considering how they interact with each other, can shift the imbalance instead of resolving it.
What This Understanding Changes
Ferritin that does not rise does not necessarily mean simply increasing the amount of iron. It invites us to look for where the lock is: in the losses, in the stomach, in the intestine, in the way iron is retained by the body, or in the cofactors—copper and B vitamins—that allow iron to be transported and transformed into hemoglobin.
When periods are heavy, the first step is to no longer consider them a feminine norm to endure. When a tablet systematically causes nausea, constipation, or digestive heaviness without sustainably improving ferritin, this poor tolerance also provides information.
And when reserves remain low despite a proper diet, the state of the stomach, PPI use, a possible H. pylori infection, an inflammatory terrain, or prolonged zinc supplementation that may have discreetly depleted copper deserve consideration.
In the diet, heme iron sources remain the most easily assimilable: meat, offal, fish, and seafood. A significant amount of calcium consumed at the same time can limit the absorption of both forms of iron. Tea and coffee mainly affect non-heme iron from plant sources; their effect on heme iron from meat remains minimal.
The quality of the meal also matters: a constantly irritated stomach, disrupted digestion, or meals eaten under tension do not create the best conditions for rebuilding reserves.
The key is to no longer view ferritin as an isolated number. Iron must enter, be absorbed, circulate, be transformed, and remain available for tissues. Understanding which stage of the process is disrupted makes it possible to ask more precise questions and finally break free from the cycle of poorly tolerated tablets, barely rising reserves, and recurring fatigue.
Periods may be the cause of the loss. They are not always the complete explanation for the deficiency. It is in this difference that the real solution begins.
DISCLAIMER: This article is for informational purposes only and does not replace personalized medical advice. The information presented aims to clarify documented biological mechanisms; any decision about your health, especially with medical conditions, ongoing treatment, or scheduled surgery, should be discussed with a qualified healthcare professional.
FAQ
Iron Deficiency Symptoms in Women: Can Fatigue Precede Anemia?
Yes, fatigue can manifest before anemia is detected. Women may experience persistent fatigue, difficulty concentrating, and hair loss, even if their hemoglobin levels remain within normal ranges. These signs are often the first indicators of iron deficiency before anemia sets in.
Low Ferritin Without Anemia: Is It Already Iron Deficiency?
Having low ferritin without anemia is possible and often indicates iron deficiency. Ferritin represents the body’s iron reserves, and a decrease in this marker shows that these reserves are depleted. Hemoglobin can remain normal as long as the available iron suffices for its production, but low ferritin requires attention to prevent the situation from worsening.
How to Determine the Cause of My Iron Deficiency?
Iron deficiency does not always have a single cause. The first step is to distinguish a true depletion of reserves from iron made unavailable by inflammation. Low ferritin generally indicates depleted reserves, while normal or elevated ferritin associated with low transferrin saturation may point to inflammatory sequestration.
Hemoglobin, transferrin saturation, and CRP help better understand the picture.
Next, examine the main possibilities: menstrual or digestive losses, insufficient intake, poor absorption linked to gastritis, PPIs, celiac disease, or H. pylori, and the possible presence of persistent inflammation. When ferritin rises but anemia or symptoms persist, other deficiencies may coexist, notably in copper, vitamin B6, B9, or B12. Prolonged zinc supplementation should also prompt consideration of copper.
The goal is not to arbitrarily choose between periods, diet, stomach, or inflammation, but to identify the step that is malfunctioning. Multiple causes can accumulate in the same person.
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