Iron Deficiency and Iron Deficiency Anemia

Iron deficiency anemia is the most common form of anemia.

What is iron, and why does the body need it?

Iron is essential for carrying oxygen and producing energy. It helps form hemoglobin, supports muscle function through myoglobin, contributes to immune function, and enables certain enzymes to work. Iron stores are held mainly in ferritin, while transferrin carries iron in the blood.

📌 Helpful fact: The body typically loses about 1–2 mg of iron each day. Every milliliter of blood lost contains approximately 0.5 mg of iron. Even small but ongoing blood losses can therefore deplete iron stores over time.

What are iron deficiency and iron deficiency anemia?

Iron deficiency

Iron deficiency means the body does not have enough iron to meet its needs. It can be present even when the hemoglobin level is still normal.

Iron deficiency anemia

Iron deficiency anemia develops when the body does not have enough iron to make hemoglobin. As the deficiency progresses, red blood cells may become smaller and contain less hemoglobin, reducing the amount of oxygen carried to tissues. In most cases, anemia develops gradually after iron stores have fallen.

How does iron deficiency develop?

Iron deficiency usually develops gradually. Iron stores decline before hemoglobin falls:

Early depletion of iron stores — Ferritin begins to fall, but hemoglobin remains normal and there are usually no symptoms.
Iron deficiency without anemia — Stores are reduced and hemoglobin may still be normal, but fatigue, difficulty concentrating, or symptoms of restless legs syndrome may appear.
Iron deficiency anemia — Hemoglobin falls, and symptoms may become more noticeable.

At first, red blood cells may remain normal in size. Microcytosis (smaller cells) and hypochromia (cells containing less hemoglobin) become more common as the anemia progresses.

What are the main causes?

Iron deficiency develops when the body loses or uses more iron than it takes in and absorbs. Common causes include:

Blood loss — Heavy menstrual periods; bleeding from the digestive or urinary tract; frequent blood donation; surgery; or other chronic blood loss.
Poor absorption — Celiac disease, autoimmune or atrophic gastritis, Helicobacter pylori infection, bariatric surgery, and certain intestinal diseases.
Increased needs — Pregnancy and periods of rapid growth in children and adolescents. Needs may also change during breastfeeding.
Inadequate intake — Very restrictive diets or a diet low in iron. In adults, diet is often not the only cause.

With inflammatory or chronic diseases, iron may be present in the body’s stores but insufficiently available for red blood cell production. This is called functional iron deficiency and is assessed differently from absolute iron deficiency. Both can occur at the same time.

Who is at risk, and when should iron levels be assessed?

Laboratory testing may be useful even without symptoms for some people at increased risk. The need for testing and how often it should be done depend on medical history and clinical circumstances. Groups that may be at higher risk include:

Women with heavy menstrual periods, pregnant women, and, in some circumstances, women who are breastfeeding.
Infants, children, and adolescents during periods of rapid growth.
Frequent blood donors and athletes who train intensively.
People whose diets are low in iron or restrictive, including poorly planned vegetarian or vegan diets.
People with digestive diseases, absorption disorders, or a history of gastric or bariatric surgery.
People with chronic inflammatory diseases, kidney disease, heart failure, or cancer.
People taking medications that may increase bleeding risk or affect iron absorption, such as anticoagulants, nonsteroidal anti-inflammatory drugs (NSAIDs), or proton pump inhibitors (PPIs).
People with inherited bleeding disorders.
Older adults, who may have several contributing causes, including hidden blood loss and chronic disease.

Having a risk factor does not necessarily mean a person has iron deficiency, but it may indicate a need for assessment, particularly when symptoms are present.

What forms can iron deficiency take?

Iron deficiency does not always develop through the same mechanism. There are two main forms, which may require different approaches.

Absolute iron deficiency — The body’s iron stores are depleted.

Functional iron deficiency — Iron stores may be normal or elevated, but not enough iron is available for red blood cell production. One important mechanism involves hepcidin, a hormone that regulates iron movement in the body. During inflammation, higher hepcidin levels restrict iron release and absorption.

What are the symptoms?

Iron deficiency may cause no symptoms in its early stages. When symptoms occur, they vary from person to person and usually become more noticeable as the deficiency worsens. Possible signs and symptoms include:

Fatigue and physical weakness.
Hair loss.
Brittle nails or, with prolonged deficiency, spoon-shaped nails (koilonychia).
Dry or rough skin.
Rarely, a bluish tint to the sclera, the white part of the eye.
Headaches and dizziness.
Cracks at the corners of the mouth (angular cheilitis) and a red, smooth, or sensitive tongue (glossitis).
Cravings for nonfood substances or starch, or a strong urge to chew ice.
Restless legs syndrome — A strong urge to move the legs, particularly in the evening or at night.
Difficulty concentrating, forgetfulness, irritability, or mood changes.

When anemia develops, pale skin or mucous membranes, shortness of breath during physical exertion, a rapid heartbeat (palpitations), and reduced exercise tolerance may also occur.

Difficulty swallowing (sideropenic dysphagia)

Rarely, prolonged iron deficiency may be associated with difficulty swallowing solid food. This requires medical assessment to identify the cause and rule out other digestive problems.

What are the warning signs?

Some signs may indicate severe anemia, active bleeding, or another serious problem and require immediate assessment.

⚠️ Seek urgent medical attention if you have bleeding that does not stop, chest pain, fainting, or severe difficulty breathing.

How are iron deficiency and iron deficiency anemia diagnosed?

Diagnosis is based on more than a complete blood count. First, the doctor assesses whether iron deficiency is present and whether anemia has developed. The next step is to identify the cause of the deficiency, particularly when it is not clear. The doctor considers symptoms, medical history, and relevant tests. The main tests include:

Complete blood count (CBC) — Measures hemoglobin, hematocrit, and red blood cell indices.
Peripheral blood smear examination and white blood cell differential — May be used in selected cases to assess cell appearance and help distinguish among possible diagnoses.
Ferritin — One of the main tests used to assess iron stores. A low result strongly supports iron deficiency. However, ferritin can rise during inflammation or infection, so a normal result does not always rule out deficiency.
Transferrin saturation (TSAT) — Shows how much iron is available for the body to use.
Other iron studies — Serum iron, transferrin or total iron-binding capacity (TIBC), and, in certain cases, soluble transferrin receptor (sTfR). These results are interpreted alongside ferritin, TSAT, and the clinical findings.

Once iron deficiency is confirmed, its cause should be investigated. Depending on age, sex, medical history, and symptoms, this may involve a gynecological assessment, tests for bleeding or poor absorption, and digestive examinations such as gastroscopy or colonoscopy.

If the cause remains unclear or laboratory results are not typical of iron deficiency, further testing may be needed for other causes of anemia, including thalassemia, chronic or inflammatory diseases, and other blood disorders.

How is it treated?

Treatment aims to correct the deficiency, restore hemoglobin when anemia is present, replenish iron stores, and identify and treat the underlying cause.

Oral iron is usually the first choice when it is tolerated and absorbed adequately.
Intravenous iron is used in selected cases, for example when oral iron is not tolerated, is poorly absorbed, or does not produce an adequate response.
Blood transfusion is reserved for particular situations, based on the severity of the anemia, symptoms, bleeding, and the patient’s clinical condition.

Diet

A balanced diet rich in iron helps prevent deficiency and supports treatment. Foods contain two forms of iron:

Heme iron comes from meat, fish, and poultry and is absorbed more easily.
Non-heme iron is found in legumes, leafy green vegetables, nuts, seeds, and fortified foods.

Foods containing vitamin C can help the body absorb non-heme iron. Tea, coffee, and calcium can reduce absorption when consumed at the same time as food or an iron preparation.

Oral iron

Iron preparations should be taken as directed by a doctor. They may cause nausea, abdominal pain, constipation or diarrhea, and dark stools. Tea, coffee, milk, calcium, antacids, and certain medications may affect absorption or interact with treatment.

Hemoglobin usually begins to rise after treatment starts, but replenishing iron stores takes longer. If the response is inadequate, the doctor reassesses possible ongoing bleeding, poor absorption, difficulty taking the preparation, active inflammation, or a different diagnosis.

Blood transfusion

Transfusion is used in selected situations, such as severe anemia with significant symptoms or active bleeding. The decision is based on the patient’s clinical condition.

📌 Do not start iron supplements without medical assessment. Normal or high ferritin can occur with inflammation and functional iron deficiency; in some cases, absolute deficiency may also be present. Test results must be interpreted together.

What complications can occur?

Untreated iron deficiency and iron deficiency anemia can affect quality of life and overall health. Their impact depends on how severe and prolonged the deficiency is.

Long-term effects

Persistent fatigue and reduced tolerance for physical activity, affecting work and daily life.
Difficulties with concentration, memory, and mood, particularly when the deficiency is prolonged.
Hair loss, brittle nails, and changes to the skin or mucous membranes, such as cracks at the corners of the mouth and a red or sensitive tongue.
Rarely, sideropenic dysphagia (Plummer–Vinson syndrome), which requires assessment because it is associated with an increased risk of esophageal cancer.
During pregnancy, an increased risk of premature birth and low birth weight.
Worsening of other conditions, such as heart failure, when anemia remains untreated.

Severe complications

Severe anemia, especially with acute blood loss, can cause a rapid heartbeat, low blood pressure, or fainting and requires urgent assessment.
In people with heart disease, severe anemia may cause angina or worsen their heart condition.

Timely diagnosis and treatment help prevent many of these effects.

Can iron deficiency be prevented?

In many cases, iron deficiency can be prevented or detected early, before iron deficiency anemia develops.

A balanced diet rich in iron plays an important role. Iron-containing foods can be combined with sources of vitamin C to improve absorption. Diet, however, is only one part of prevention. Identifying and treating causes of blood loss or poor iron absorption—such as heavy menstrual periods, chronic bleeding, or digestive diseases—is equally important.

For people at higher risk, tests recommended by a doctor may detect deficiency before significant symptoms or anemia develop. Iron supplements should not be taken routinely without an identified reason. The doctor assesses whether a deficiency is present, what is causing it, and whether treatment is needed.

When should you consult a doctor?

Consult a doctor if:

Persistent fatigue, paleness, dizziness, shortness of breath, or a rapid heartbeat develops, continues, returns, or worsens.
You have very heavy or prolonged menstrual periods, blood in your stool or urine, or black stools.
You have difficulty swallowing, unexplained weight loss, or persistent changes in how often you pass stools or in their shape or color.
Iron deficiency returns after treatment.
A routine test shows iron deficiency or anemia, even if you have no symptoms.

Frequently asked questions

Can iron deficiency cause symptoms without anemia?
Yes. Even when hemoglobin is normal, iron deficiency may be associated with symptoms because iron is also needed for the muscles, brain, and other processes in the body. Symptoms may have other causes, so they should be assessed alongside test results.

Are tests useful even without noticeable symptoms?
For some people with risk factors, tests can identify iron deficiency before anemia develops and help uncover its cause. The need for testing depends on individual risk.

Is diet enough to treat iron deficiency?
An iron-rich diet is important for prevention and supports treatment. Once deficiency or anemia has developed, diet alone is often insufficient to replenish iron stores. Iron treatment may be needed along with treatment of the underlying cause.

What happens after treatment?
The doctor assesses the response to treatment and whether further follow-up is needed. If the cause has been corrected, checkups may become less frequent over time. If it persists, as with some chronic diseases or repeated blood loss, regular follow-up may be necessary. A return of symptoms calls for reassessment.

Can iron deficiency be fully treated?
Yes. In most cases, the deficiency can be corrected. Treatment also involves identifying the cause; if the cause remains, iron deficiency may return.

How quickly will I improve with treatment?
Some symptoms may improve within the first few weeks, but the timing varies. Hemoglobin usually rises gradually, and returning to a normal level may take several weeks or longer, depending on the severity and cause of the anemia. Replenishing iron stores takes more time, so treatment should not be stopped simply because hemoglobin has normalized.

How often should tests be done?
The frequency depends on risk, symptoms, and previous results. No single interval is appropriate for everyone. For people at increased risk, the doctor may request a complete blood count and ferritin test because iron deficiency can be present without anemia.

Why does oral iron sometimes fail to work?
Possible reasons include ongoing bleeding, poor absorption, irregular use of the preparation, active inflammation, or another cause of anemia. In these cases, the doctor reassesses the diagnosis and decides whether treatment should change, including whether intravenous iron is appropriate.

Why does finding the cause matter?

Iron deficiency and iron deficiency anemia can be treated successfully in most cases. Early diagnosis, confirmation through testing, and identification of the cause help ensure that treatment is appropriate and the deficiency does not return. If you have symptoms or risk factors, consult a doctor for an assessment.

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📌 Reviewed by Dr. Irma Lapaj, Hematologist, Klinika Kajo.

Iron Deficiency and Iron Deficiency Anemia