Iron Deficiency: Symptoms, Causes, Diagnosis & Treatment

Understanding Iron Deficiency

Iron deficiency is one of the most common nutritional deficiencies worldwide, affecting people of all ages. Iron is an essential mineral that plays a fundamental role in transporting oxygen throughout the body, producing energy and supporting normal immune function.

When iron levels become too low, the body's ability to produce healthy red blood cells gradually declines. As a result, tissues receive less oxygen, leading to symptoms such as fatigue, weakness and reduced physical performance. If left untreated, iron deficiency may eventually progress to iron deficiency anaemia.

Although iron deficiency is often associated with poor dietary intake, many cases are caused by chronic blood loss, gastrointestinal disorders or conditions that reduce iron absorption. Identifying the underlying cause is therefore just as important as correcting the deficiency itself.

This article explains the role of iron in the body, the symptoms of iron deficiency, how it develops and why early diagnosis is important.

What Is Iron?

Iron is an essential mineral that the body requires to produce haemoglobin, the protein inside red blood cells responsible for carrying oxygen from the lungs to the body's tissues.

Iron is also involved in:

Energy production
Muscle function
DNA synthesis
Brain function
Immune system activity
Normal cell growth

Because the body cannot produce iron, it must be obtained through diet or, when medically indicated, supplementation.

Why Is Iron Important?

Every organ depends on a continuous supply of oxygen.

Iron enables red blood cells to transport oxygen efficiently throughout the body. Without sufficient iron, oxygen delivery gradually becomes less effective, affecting both physical and mental performance.

Iron also contributes to:

Normal cognitive function
Exercise capacity
Muscle metabolism
Healthy pregnancy
Immune defence
Cellular energy production

Even before anaemia develops, low iron stores may cause noticeable symptoms in some individuals.

How Iron Is Stored in the Body

Unlike some vitamins, iron is carefully recycled and conserved by the body.

Most iron is found within haemoglobin inside red blood cells, while smaller amounts are stored in the liver, spleen and bone marrow.

The body's primary iron storage protein is ferritin.

Ferritin acts as the body's iron reserve, releasing iron when needed for the production of new red blood cells.

Because ferritin levels often fall before haemoglobin decreases, measuring ferritin is one of the most useful ways to detect early iron deficiency.

Iron Deficiency vs Iron Deficiency Anaemia

These terms are often used interchangeably, but they are not the same.

Iron deficiency means that the body's iron stores have become depleted.

Iron deficiency anaemia develops later, when iron stores become so low that the body can no longer produce enough healthy red blood cells.

This distinction is important because symptoms may begin long before anaemia appears on a routine blood test.

Early Symptoms of Iron Deficiency

The earliest symptoms are often subtle and develop gradually.

Common symptoms include:

Persistent fatigue
Low energy
Weakness
Reduced exercise tolerance
Difficulty concentrating
Brain fog
Dizziness
Headaches
Feeling cold more easily

Because these symptoms are non-specific, they may initially be attributed to stress, poor sleep or a busy lifestyle.

Symptoms of More Advanced Iron Deficiency

As iron levels continue to fall, symptoms may become more noticeable.

These include:

Shortness of breath during physical activity
Palpitations
Pale skin
Brittle nails
Hair thinning or increased hair loss
Restless legs syndrome
Reduced physical performance
Chest discomfort during exertion in severe cases

If iron deficiency progresses to anaemia, symptoms generally become more pronounced.

Can Iron Deficiency Affect the Brain?

Yes.

Iron is essential for normal brain function.

Some individuals with iron deficiency experience:

Brain fog
Difficulty concentrating
Poor memory
Reduced productivity
Difficulty maintaining attention

Although these symptoms have many possible causes, iron deficiency is one condition that doctors commonly investigate when they persist.

Can You Have Iron Deficiency Without Anaemia?

Yes.

Many patients have low ferritin levels while their haemoglobin remains completely normal.

These individuals may still experience symptoms such as:

Fatigue
Reduced exercise performance
Difficulty concentrating
Hair loss
Restless legs

This is one reason why doctors may recommend measuring ferritin even when the complete blood count appears normal.

Who Is Most at Risk?

Iron deficiency can affect anyone, but some groups are at higher risk.

These include:

Women with heavy menstrual bleeding
Pregnant women
Frequent blood donors
Infants and young children
Adolescents during periods of rapid growth
Vegetarians and vegans
Endurance athletes
Older adults
People with gastrointestinal disorders

Recognising these risk factors allows earlier diagnosis before complications develop.

Why Early Diagnosis Matters

Iron deficiency should never be viewed as a diagnosis in itself.

Instead, it is often a sign that an underlying problem requires investigation.

While dietary insufficiency is one possible explanation, doctors also consider:

Gastrointestinal bleeding
Heavy menstrual bleeding
Reduced intestinal absorption
Chronic inflammatory diseases
Other medical conditions

Identifying and treating the underlying cause helps prevent the deficiency from recurring.

What Causes Iron Deficiency?

Iron deficiency develops when the body's iron requirements exceed the amount of iron that is absorbed or stored.

This may occur gradually over months or even years and is often the result of one or more underlying medical conditions rather than diet alone.

Understanding the cause is essential because treatment should address not only the deficiency itself but also the reason why it developed.

1. Blood Loss

Chronic blood loss is one of the most common causes of iron deficiency.

Even small amounts of ongoing blood loss can gradually deplete the body's iron stores.

Common sources include:

Heavy menstrual bleeding
Gastrointestinal bleeding
Stomach ulcers
Colon polyps
Colorectal cancer
Haemorrhoids (less commonly a significant cause)
Frequent blood donation
Surgery or traumatic injury

In adults—particularly men and postmenopausal women—iron deficiency often prompts doctors to investigate for possible gastrointestinal bleeding.

2. Heavy Menstrual Bleeding

Women of reproductive age are among the groups most frequently affected by iron deficiency.

Heavy or prolonged menstrual bleeding may gradually reduce iron stores over time.

Women may not realise that their periods are unusually heavy because the change often develops slowly.

Symptoms may include:

Fatigue
Reduced exercise tolerance
Dizziness
Shortness of breath
Poor concentration

Medical evaluation may be recommended if menstrual bleeding is unusually heavy or associated with symptoms of iron deficiency.

3. Inadequate Dietary Iron Intake

Diet alone is not the most common cause, but it can contribute.

Iron-rich foods include:

Red meat
Poultry
Fish
Eggs
Lentils
Beans
Chickpeas
Tofu
Spinach
Pumpkin seeds

Plant-based diets can provide adequate iron, although the form of iron found in plants (non-haem iron) is generally absorbed less efficiently than the haem iron found in animal products.

Combining plant sources of iron with foods rich in vitamin C may help improve absorption.

4. Reduced Iron Absorption

Some individuals consume enough iron but are unable to absorb it efficiently.

Possible causes include:

Coeliac disease
Inflammatory bowel disease
Previous stomach or intestinal surgery
Chronic gastritis
Helicobacter pylori infection
Long-term use of proton pump inhibitors (PPIs)

When malabsorption is suspected, doctors investigate the underlying gastrointestinal condition rather than simply recommending iron supplements.

5. Pregnancy

Pregnancy significantly increases the body's iron requirements.

Iron is needed to support:

Expansion of maternal blood volume
Foetal growth
Placental development

For this reason, iron deficiency is relatively common during pregnancy and may be identified through routine antenatal blood tests.

6. Increased Physical Demands

Athletes and highly active individuals may have increased iron requirements.

Several factors contribute, including:

Increased red blood cell production
Iron loss through sweating
Repetitive impact during endurance sports
Higher metabolic demands

Endurance runners, cyclists and competitive athletes are among the groups most commonly assessed for iron deficiency when unexplained fatigue develops.

7. Gastrointestinal Disorders

Several digestive conditions may reduce iron absorption or cause chronic blood loss.

Examples include:

Coeliac disease
Crohn's disease
Ulcerative colitis
Gastric ulcers
Chronic gastritis

These conditions require appropriate medical diagnosis and management in addition to correcting iron deficiency.

How Is Iron Deficiency Diagnosed?

Symptoms alone cannot confirm iron deficiency.

A diagnosis is usually made through a combination of:

Medical history
Clinical assessment
Physical examination
Blood tests

The objective is to determine both the presence of iron deficiency and its underlying cause.

Blood Tests Used to Assess Iron Deficiency

Several laboratory tests may be recommended.

These commonly include:

Full Blood Count (FBC)
Ferritin
Serum Iron
Transferrin
Transferrin Saturation (TSAT)
Total Iron Binding Capacity (TIBC)
C-Reactive Protein (CRP), when inflammation is suspected

Additional investigations may be appropriate depending on the individual's symptoms and medical history.

What Is Ferritin?

Ferritin is the body's main iron storage protein.

Measuring ferritin provides valuable information about the amount of iron stored within the body.

Low ferritin is often the earliest laboratory sign of iron deficiency, even before anaemia develops.

However, ferritin is also an inflammatory marker and may appear normal or elevated during infection or chronic inflammatory disease.

For this reason, doctors interpret ferritin alongside other blood test results and the overall clinical picture.

Why Finding the Cause Matters

Correcting iron deficiency without identifying its cause may only provide a temporary solution.

For example:

Iron supplements cannot stop ongoing blood loss.
They cannot treat coeliac disease.
They cannot diagnose bowel disease.
They cannot identify underlying gastrointestinal pathology.

A thorough medical assessment helps determine why iron deficiency developed and guides the most appropriate treatment plan.

When Should You See a Doctor?

Medical assessment is recommended if you experience:

Persistent fatigue
Unexplained weakness
Shortness of breath
Frequent dizziness
Hair loss
Heavy menstrual bleeding
Blood in the stool
Ongoing digestive symptoms
Recurrent iron deficiency despite treatment

Early assessment allows the underlying cause to be investigated before more significant complications develop.

How Is Iron Deficiency Treated?

The most appropriate treatment depends on the underlying cause, the severity of the deficiency and the individual's overall health.

The primary goals of treatment are to:

Restore normal iron levels
Replenish the body's iron stores
Improve symptoms
Identify and treat the underlying cause
Prevent recurrence

Treatment should always be guided by an appropriate medical assessment rather than starting supplements without investigation.

Dietary Changes

For individuals with mild iron deficiency, improving dietary iron intake may form part of the treatment plan.

Iron-rich foods include:

Lean red meat
Poultry
Fish
Seafood
Eggs
Lentils
Chickpeas
Beans
Tofu
Pumpkin seeds
Spinach

Vitamin C-rich foods, such as citrus fruits, berries, peppers and tomatoes, may improve the absorption of non-haem iron from plant-based foods.

Conversely, tea, coffee and calcium-rich foods may reduce iron absorption when consumed with iron-rich meals or iron supplements.

Oral Iron Supplements

Oral iron supplementation is commonly recommended for individuals with confirmed iron deficiency.

Treatment usually continues for several months, even after symptoms improve, to allow the body's iron stores to recover.

Some people experience side effects, including:

Constipation
Nausea
Abdominal discomfort
Dark stools
Bloating

Because these side effects may reduce adherence, doctors sometimes adjust the dose or recommend taking iron on alternate days to improve tolerability.

Patients should only take iron supplements following medical advice, as excessive iron intake may be harmful.

When Is Intravenous Iron Considered?

Intravenous (IV) iron may be considered when oral iron is unsuitable or ineffective.

Examples include:

Inability to tolerate oral iron
Poor intestinal absorption
Ongoing inflammatory bowel disease
Severe iron deficiency requiring more rapid correction
Persistent deficiency despite appropriate oral treatment
Certain situations during pregnancy when clinically indicated

IV iron should only be administered following a medical assessment and when considered appropriate by the treating physician.

How Long Does Recovery Take?

Recovery varies depending on the severity of the deficiency and its underlying cause.

Many individuals begin to notice improvements in symptoms within a few weeks of starting treatment.

However, restoring iron stores generally takes longer.

Doctors often recommend continuing treatment after haemoglobin has normalised to fully replenish iron reserves and reduce the risk of recurrence.

Follow-up blood tests are commonly used to monitor recovery.

Can Iron Deficiency Return?

Yes.

Iron deficiency may recur if the underlying cause is not identified or successfully treated.

Examples include:

Persistent heavy menstrual bleeding
Ongoing gastrointestinal blood loss
Untreated coeliac disease
Chronic inflammatory bowel disease
Inadequate dietary intake
Increased iron requirements

For recurrent iron deficiency, further medical investigation may be necessary.

Can Iron Deficiency Be Prevented?

Prevention depends largely on the underlying cause.

Strategies may include:

Eating a balanced diet containing adequate iron
Treating heavy menstrual bleeding when appropriate
Managing gastrointestinal conditions
Monitoring iron status during pregnancy
Regular medical review in individuals at increased risk

People with a history of recurrent iron deficiency may benefit from periodic blood tests under medical supervision.

Frequently Asked Questions

What is the first sign of iron deficiency?

Early symptoms often include fatigue, reduced energy levels, difficulty concentrating and decreased exercise tolerance. These symptoms may develop before anaemia is present.

Can you have normal haemoglobin but low iron?

Yes.

Ferritin, which reflects the body's iron stores, may become low before haemoglobin levels fall. Some people experience symptoms despite having a normal full blood count.

Is iron deficiency the same as anaemia?

No.

Iron deficiency refers to depleted iron stores.

Iron deficiency anaemia develops later, when iron stores become so low that the body cannot produce enough healthy red blood cells.

Should I take iron supplements without a blood test?

Iron supplements should not be started routinely without medical advice.

Symptoms such as fatigue have many possible causes, and excessive iron supplementation may be harmful in some individuals.

A medical assessment and appropriate blood tests help determine whether iron deficiency is present and identify its underlying cause.

Does everyone with iron deficiency need intravenous iron?

No.

Many people respond well to dietary measures or oral iron supplementation.

Intravenous iron is reserved for selected situations where it is considered medically appropriate.

When Should You Seek Medical Advice?

Medical assessment is recommended if you experience:

Persistent fatigue
Ongoing weakness
Shortness of breath
Frequent dizziness
Heavy menstrual bleeding
Unexplained hair loss
Recurrent iron deficiency
Blood in the stool
Persistent digestive symptoms

Early diagnosis helps identify both the deficiency and any underlying medical condition that may require treatment.

Key Takeaways

Iron deficiency is one of the most common nutritional deficiencies worldwide and may affect energy levels, physical performance and overall wellbeing.

Because many different medical conditions can lead to iron deficiency, identifying the underlying cause is an essential part of treatment. Blood tests—including ferritin and a full blood count—play a central role in diagnosis and help guide appropriate management.

While dietary changes and oral iron supplements are effective for many individuals, some people may require further investigation or alternative treatment approaches depending on their clinical circumstances.

A personalised medical assessment allows treatment to be tailored to the individual and helps reduce the risk of recurrent iron deficiency.

About Dr. Indhira Ghyssaert

Dr. Indhira Ghyssaert is a General Practitioner with a special interest in preventive, integrative and personalised medicine. She provides comprehensive medical assessments designed to identify the underlying causes of symptoms rather than simply treating them in isolation.

At Galatzó Health, Dr. Ghyssaert combines evidence-based medicine with advanced laboratory testing and personalised treatment plans to help patients optimise their health and wellbeing.

Medical Disclaimer

This article is intended for informational and educational purposes only and should not be considered a substitute for professional medical advice, diagnosis or treatment.

Iron deficiency can have many different causes, some of which may require prompt medical investigation. If you experience persistent fatigue, weakness, shortness of breath, dizziness or any other concerning symptoms, you should seek assessment from a qualified healthcare professional.

Never start iron supplementation without appropriate medical advice, as excessive iron intake may be harmful and symptoms may be caused by conditions other than iron deficiency.

Book a Medical Assessment

If you are experiencing symptoms that may be related to iron deficiency, a personalised medical assessment can help identify the underlying cause and determine whether further investigations or treatment are appropriate.

At Galatzó Health in Mallorca, consultations are led by Dr. Indhira Ghyssaert and may include: