Iron Deficiency: Why Low Iron Is More Than Just Anaemia

Feeling unusually tired, struggling to concentrate or noticing that everyday exercise suddenly feels harder than it used to? Iron deficiency is often associated with anaemia, but the two are not exactly the same — and iron stores can become depleted before haemoglobin levels fall below the normal range.

This means that a seemingly normal haemoglobin result does not always tell the whole story.

Understanding iron deficiency is not only about replacing the missing iron. The more important question is often: why is the iron low in the first place?

Iron is an essential mineral with several important functions. Most notably, it is required to produce haemoglobin, the protein inside red blood cells that carries oxygen from the lungs to tissues throughout the body.

But its role goes beyond haemoglobin. Iron also contributes to normal energy metabolism, muscle function and numerous cellular processes.

When the body gradually loses more iron than it absorbs, it first begins to use its stored reserves. If the imbalance continues, those stores become depleted and eventually the production of healthy red blood cells can be affected.

These terms are often used interchangeably, but they describe different stages of the same process.

Iron deficiency means that the body’s available iron and iron stores are reduced.

Iron-deficiency anaemia develops later, when the deficiency becomes significant enough to interfere with haemoglobin production and the haemoglobin concentration falls below the normal range.

In other words, it is possible to have iron deficiency without being anaemic.

This is one reason why checking haemoglobin alone may not be sufficient when iron deficiency is suspected. Ferritin, which reflects the body’s iron stores, is one of the most useful laboratory markers when assessing iron status.

The symptoms can be subtle and are not specific to iron deficiency. Some people have very few symptoms, particularly in the early stages.

Others may experience:

• persistent tiredness or lack of energy
• reduced exercise capacity
• weakness
• shortness of breath, particularly during physical activity
• headaches or dizziness
• palpitations
• difficulty concentrating
• restless legs
• hair loss or changes in hair quality
• brittle nails

As iron deficiency progresses to anaemia, symptoms may become more noticeable because the blood’s ability to transport oxygen is increasingly affected.

However, these symptoms can have many different causes. Fatigue or hair loss alone, for example, should not automatically be attributed to iron deficiency without appropriate testing.

Iron deficiency develops when iron losses or requirements exceed the amount of iron the body is able to absorb.

There are several possible reasons.

Blood loss

Blood loss is one of the most important causes because blood itself contains iron.

In menstruating women, heavy or prolonged menstrual bleeding is a common cause. Gastrointestinal blood loss can also gradually deplete iron stores and may occur without visible blood in the stool.

Other potential sources include repeated blood donation or, less commonly, bleeding from another part of the body.

Increased iron requirements

The body’s demand for iron increases during certain stages of life.

Pregnancy is a particularly important example because additional iron is required to support the expansion of maternal blood volume and the developing fetus.

Children and adolescents also have increased requirements during periods of rapid growth.

Reduced absorption

A person may consume enough iron but still be unable to absorb it adequately.

Conditions affecting the gastrointestinal tract, including coeliac disease and certain inflammatory bowel diseases, can interfere with iron absorption. Previous gastric or intestinal surgery may also reduce the body’s ability to absorb iron effectively.

Insufficient dietary intake

Diet can contribute as well, particularly when iron intake is low for a prolonged period or when increased requirements are not matched by dietary intake.

However, finding iron deficiency should not automatically lead to the conclusion that diet is the only explanation. The clinical context matters.

Iron deficiency is particularly common in women of reproductive age, largely because of menstrual blood loss and the increased iron requirements associated with pregnancy.

Heavy periods are an especially important clue.

But repeatedly low iron should not simply be accepted as something a woman has to live with.

If menstrual bleeding is excessive, the reason for the bleeding itself may need to be assessed. Depending on the patient’s history, this may involve a gynaecological evaluation in addition to blood tests and iron replacement.

Pregnancy and the postpartum period can also significantly affect iron stores, particularly when iron requirements were already increased during pregnancy or when there was substantial blood loss around delivery.

The goal is therefore not only to restore iron levels, but also to understand what caused them to fall.

The situation deserves particular attention when iron-deficiency anaemia develops in a man or a postmenopausal woman without an obvious explanation.

In these groups, chronic gastrointestinal blood loss becomes an important possibility.

Potential causes range from relatively common gastrointestinal conditions to ulcers, inflammatory disease or, less commonly but importantly, gastrointestinal malignancy.

This does not mean that iron deficiency automatically indicates cancer. It means that unexplained iron-deficiency anaemia in these patients should not simply be treated with supplements without considering where the iron is being lost.

Depending on age, symptoms, medical history and laboratory results, further gastrointestinal investigation may therefore be recommended.

Diagnosis usually begins with a blood test, but no single number should be interpreted entirely in isolation.

Complete blood count

A complete blood count provides information about haemoglobin and red blood cells.

In established iron-deficiency anaemia, haemoglobin is reduced and characteristic changes in red blood cell size and haemoglobin content may appear.

Earlier in the process, however, haemoglobin may still remain within the normal range.

Ferritin

Ferritin is one of the most useful markers of the body’s iron stores.

A clearly low ferritin level strongly supports iron deficiency. But interpretation becomes more complicated in people with inflammation, infection or certain chronic conditions.

Why?

Because ferritin is also an acute-phase protein. Its concentration can rise in response to inflammation. As a result, a person may have depleted iron availability while their ferritin appears normal — or even elevated.

Transferrin saturation and other tests

When the situation is less straightforward, doctors may also assess parameters such as transferrin saturation and markers of inflammation such as C-reactive protein (CRP).

Together with the complete blood count, ferritin and the patient’s clinical history, these results can provide a much clearer picture than haemoglobin alone.

Once iron deficiency has been confirmed, the next question should be:

What caused it?

The answer may be relatively straightforward — for example, heavy menstrual bleeding or increased requirements during pregnancy.

In other cases, further investigation may be appropriate.

Depending on the individual patient, this can include assessment for coeliac disease, gastrointestinal evaluation, gynaecological examination or other targeted tests.

This is particularly important when iron deficiency is severe, recurrent, does not respond as expected to treatment or has no obvious explanation.

Treatment depends on both the severity of the deficiency and its underlying cause.

For many patients, oral iron supplementation is the first approach. Treatment usually needs to continue long enough not only to improve haemoglobin, when anaemia is present, but also to restore depleted iron stores.

Oral iron can cause gastrointestinal side effects such as nausea, abdominal discomfort, constipation or diarrhoea. The type of preparation and dosing schedule can therefore sometimes be adjusted to improve tolerance.

Intravenous iron may be appropriate in selected situations — for example, when oral iron is poorly tolerated, absorption is impaired, replacement is needed more rapidly or oral treatment has not produced an adequate response.

But replacing iron is only one part of treatment.

If the underlying cause continues — whether it is heavy menstrual bleeding, gastrointestinal blood loss or impaired absorption — iron deficiency may return.

It may be worth discussing iron testing with a doctor if you experience persistent unexplained fatigue, reduced physical performance or other compatible symptoms, particularly if you also have risk factors such as heavy menstrual bleeding, pregnancy, previous gastrointestinal disease or a history of iron deficiency.

Medical assessment is particularly important when:

• iron deficiency or anaemia keeps returning
• iron levels do not improve as expected despite treatment
• there is no obvious reason for the deficiency
• iron-deficiency anaemia develops in a man or postmenopausal woman
• gastrointestinal symptoms are present
• there is unusual or persistent bleeding

The appropriate investigation will be different for every patient.

Iron deficiency is often easy to detect and, in many cases, straightforward to treat. What should not be overlooked is the reason it developed.

A blood test can identify depleted iron stores. A more complete medical assessment can help explain why they became depleted and whether anything else needs attention.

For patients who would like to investigate iron deficiency in Barcelona, Barcelona Medical Consulting can coordinate the process from the initial assessment onwards. Depending on your medical history and previous results, this may include laboratory testing and consultation with an internal medicine specialist, gynaecologist or gastroenterologist, as well as further diagnostic examinations when medically indicated.

If you already have recent blood tests showing low ferritin, low iron or anaemia, you can also send us your results in advance. We can help organise the appropriate medical evaluation in Barcelona and coordinate the necessary appointments with the relevant specialists — so that the assessment focuses not only on correcting the deficiency, but on understanding its cause.