OVERVIEW

What is Iron Deficiency Anemia?

Iron deficiency anemia, a type of anemia caused by insufficient iron, is the most common form of anemia.

Anemia refers to a condition where the concentration of red blood cells or hemoglobin in the peripheral blood is lower than normal. Hemoglobin is the main component of red blood cells, enabling them to transport oxygen.

When hemoglobin levels are low, the body may not receive adequate oxygen supply. Hemoglobin is an iron-containing protein that requires iron for synthesis. If iron is insufficient, the production of hemoglobin and red blood cells is affected.

Who is Prone to Iron Deficiency Anemia?

Iron deficiency anemia is the most prevalent type of anemia, occurring worldwide across all ethnicities and age groups. It is particularly common in women of childbearing age and infants.

Why Does Iron Deficiency Anemia Occur?

Iron deficiency anemia occurs when iron supply cannot meet demand. The main causes fall into three categories:

• Increased Demand with Inadequate Intake: Common in infants, adolescents, and pregnant or lactating women. Higher demand combined with insufficient intake increases the risk.

• Impaired Iron Absorption: Often seen in patients after gastrectomy or those with chronic diarrhea or inflammatory bowel disease.

• Excessive Iron Loss: Primarily occurs in patients with chronic blood loss or those experiencing acute, significant blood loss.

Does Iron Deficiency Always Lead to Anemia?

No. The progression from iron deficiency to anemia involves stages. Typically, iron imbalance in the body occurs in three phases:

• Iron Depletion: Iron is stored in the body as a "strategic reserve," mainly in the liver, spleen, and bone marrow. Adult males have about 10 mg per kg of body weight, while females have less. Depletion means reserves are exhausted, but circulating iron from red blood cell metabolism still supports normal hemoglobin production.

• Erythrocyte Iron Deficiency: Further iron loss without replenishment reduces iron availability for red blood cell production, leading to low mean corpuscular volume and reticulocyte hemoglobin content.

• Iron Deficiency Anemia: The final stage, where hemoglobin concentration decreases.

SYMPTOMS

What are the symptoms of iron deficiency anemia?

• In addition to being involved in hemoglobin production, iron is also associated with various other physiological activities in the human body. The symptoms of iron deficiency anemia are not necessarily caused by "anemia" alone but may also result from "iron deficiency" itself. While the general public does not need to distinguish between the two, it is important to be aware of this.

• Among adults, some patients may have no symptoms. For those who do experience symptoms, the following are common manifestations:

  • Fatigue: Iron deficiency anemia can impair motor function, leading to general weakness.
  • Easy exhaustion: Patients may experience reduced exercise tolerance and feel tired quickly after physical activity.
  • Exertional dyspnea: Difficulty breathing after physical exertion. Due to insufficient hemoglobin, some patients may attempt to compensate by increasing oxygen intake through rapid breathing during activities (exercise or manual labor).
  • Pica and pagophagia: Pica refers to a strong craving for non-food items. Patients with iron deficiency anemia may exhibit pica, desiring substances such as raw starch, uncooked rice, soil, dust, stones, or paper products. Additionally, some may develop a preference for ice, which often resolves quickly after iron supplementation.
  • Restless legs syndrome (RLS): A specific sleep disorder where patients experience an uncontrollable urge to move their legs, especially at rest or during the evening. Movement typically relieves the discomfort. RLS is now recognized as one of the common clinical manifestations of iron deficiency.
  • Headache: Iron deficiency anemia can cause headaches.
  • Dry mouth: Some patients may experience dry mouth.
  • Beeturia: Beetroots and red dragon fruits contain betalain, a red pigment. Iron ions can decolorize it. In cases of iron deficiency, absorbed betalain is excreted in urine, turning it red. However, beeturia is not specific to iron deficiency anemia and can occur in healthy individuals as well.
  • Physical changes: Abnormalities in complexion, nails, and lip color, often presenting as pallor. As anemia progresses, the skin may become rough and cracked. Some patients develop "koilonychia," where nails thin out, becoming concave with raised edges.
  • Tachycardia: Severe anemia may lead to a rapid heart rate. The severity of these symptoms varies. Some patients only recall experiencing them after being diagnosed with iron deficiency. Moreover, these symptoms are not exclusive to iron deficiency anemia. Therefore, if any of these signs appear, prompt medical consultation is advised.

• Adolescents (12–18 years old) In addition to the symptoms seen in adults, iron deficiency in adolescents may impair cognitive function. Iron supplementation can improve cognitive abilities, such as verbal expression and memory.

• Children and infants (0–12 years old) Beyond the symptoms mentioned in the "Adults" section, iron deficiency anemia in children and infants has additional notable manifestations:

  • Impaired cognitive development: As mentioned earlier, iron deficiency is a progressive condition. Even before anemia develops, iron deficiency can negatively affect neurological development in children, impairing cognitive function. Iron deficiency may slow visual and auditory processing in infants and toddlers, as well as cause behavioral abnormalities such as lethargy, apathy, and disinterest in surroundings. School-aged children may struggle with concentration and memory. Severe iron deficiency can lead to further cognitive impairment. While iron therapy can correct the deficiency, some children may fully recover, whereas others may experience long-term deficits or fail to reach age-appropriate developmental levels.

  • Febrile seizures: Seizures triggered by elevated body temperature in children. Although no direct evidence links iron deficiency to febrile seizures, studies show that children with febrile seizures often have iron deficiency, suggesting a clear association.

  • Pica: In addition to the details in the "Adults" section, parents should be alert to children putting non-food items in their mouths.

How does iron deficiency anemia in pregnant women affect the fetus?

• Mild iron deficiency anemia generally has no significant impact on the fetus. However, timely medical consultation and intervention under a doctor's guidance are essential.

• Severe anemia (including anemia from other causes) can lead to serious consequences. The mother and fetus are connected via the placenta and umbilical cord. Severe iron deficiency anemia may cause placental abnormalities, increasing the risk of adverse effects on fetal development and raising the likelihood of complications. Additionally, childbirth is physically demanding. Severe anemia, often accompanied by exertional dyspnea and tachycardia, poses significant risks to maternal safety during delivery.

CAUSES

Which groups are at high risk for iron deficiency anemia?

In China, it mainly includes:

• Children: Primarily due to insufficient iron intake during growth and development.
• Women of childbearing age: Mainly related to pregnancy, childbirth, and menstrual blood loss.
• Elderly: Reduced absorption capacity and higher prevalence of chronic diseases increase the risk of iron deficiency anemia.
• Low-income groups: Often caused by malnutrition or delayed diagnosis and treatment of diseases.
• Vegetarians: Some individuals adopt vegetarian diets due to religious beliefs or other reasons. Since animal meat and organ meats are rich in iron and more bioavailable than plant-based iron sources, vegetarians face a higher risk of iron deficiency anemia.
• Patients with chronic diseases.

What are the main causes of iron deficiency anemia?

The causes of iron deficiency anemia in infants and children under 12 differ from those in adults. The former is primarily due to dietary factors, while the latter is more related to various forms of blood loss.

• Perinatal issues (from 28 weeks of pregnancy to one week postpartum):

  • Severe iron deficiency anemia in the mother;
  • Perinatal bleeding in newborns;
  • Premature birth: Preterm infants are prone to iron deficiency anemia due to insufficient maternal iron supply, lower blood volume at birth, and poor digestion and absorption. The earlier the gestational age, the lower the iron reserves in the newborn.
  • Inadequate iron intake in newborns.

• Dietary reasons:

  • Insufficient iron intake: After 6 months of age, a child's iron requirements increase. Breastfed infants may develop iron deficiency anemia if not supplemented appropriately. For non-breastfed infants, formula selection should match the child's age.
  • Low iron absorption efficiency: Children from low-income families with limited access to meat may develop iron deficiency anemia. Picky eating can also contribute.
  • Early or excessive cow's milk consumption: Introducing cow's milk too early or in excessive amounts can cause intestinal blood loss due to intolerance, leading to iron deficiency anemia.

• Blood loss is a major cause of iron deficiency anemia, as blood loss requires iron for hematopoiesis. Insufficient iron supply leads to deficiency. Causes include:

  • Heavy or abnormal uterine bleeding;
  • Childbirth;
  • Gastrointestinal bleeding: Manifestations include hematemesis, melena, and occult blood in stool;
  • Hemorrhoids;
  • Urinary tract bleeding: Tumors, stones, and inflammatory diseases can cause chronic blood loss sufficient to induce iron deficiency anemia;
  • Respiratory bleeding: Mainly blood in sputum, possibly due to tracheal, bronchial, pulmonary, or vascular disorders;
  • Trauma or surgical bleeding;
  • Rare systemic diseases, such as hereditary hemorrhagic telangiectasia.

• Reduced iron absorption: The body primarily absorbs dietary iron through the upper gastrointestinal mucosa, especially the duodenum. Elderly individuals may develop iron deficiency anemia due to declining absorption capacity. Other high-risk groups include patients with chronic gastritis, peptic ulcers, inflammatory bowel disease, celiac disease, intestinal parasitic infections, or post-gastrectomy/duodenectomy.

• Pregnancy

• Chronic kidney disease

• Other rare causes: Such as myelodysplastic syndrome, paroxysmal nocturnal hemoglobinuria, autoimmune hemolytic anemia, and iron-refractory iron deficiency anemia.

DIAGNOSIS

How is iron deficiency anemia diagnosed?

According to China's current diagnostic criteria, microcytic hypochromic anemia meeting any one of the following conditions is considered iron deficiency anemia:

• Clear evidence of iron deficiency etiology and clinical manifestations;
• Serum ferritin < 14 μg/L (some international guidelines suggest a cutoff of 30 μg/L);
• Serum iron < 8.95 μmol/L with total iron-binding capacity > 64.44 μmol/L;
• Transferrin saturation < 0.15;
• Bone marrow iron staining shows absence of stainable iron in marrow spicules and < 15% sideroblasts;
• Positive response to iron supplementation therapy;
• Other less commonly performed iron-related tests.

Note: Cutoff values may vary between hospitals due to equipment or academic differences. Patients need only focus on the diagnostic conclusion.

What tests are needed for iron deficiency anemia?

Typically, a complete blood count (CBC) and serum iron profile (four tests) are required. These include multiple parameters sufficient for diagnosis. Additional tests may be needed when necessary.

• Complete blood count (CBC)
• Serum iron profile (four tests)
• C-reactive protein (CRP)
• Bone marrow aspiration
• Tests to identify the cause of iron deficiency may include:
  • If no clear medical history exists: H. pylori breath test, fecal occult blood, gastroscopy, or colonoscopy.
  • For menorrhagia or abnormal uterine bleeding: gynecological evaluation.
  • Suspected iron-refractory iron deficiency anemia: TMPRSS6 gene testing.

Does low serum iron always indicate iron deficiency anemia?

No. While serum iron is reduced in iron deficiency anemia, it may also be low in other types of anemia. Comprehensive analysis of test results is essential.

TREATMENT

Which department should I visit for iron deficiency anemia?

• If you only want a check-up, go directly to the general outpatient department.
• Children under 14 should visit the pediatric or child healthcare department.
• Patients diagnosed with iron deficiency anemia who require further evaluation and treatment should visit the hematology department.
• Pregnant patients should visit the obstetrics department.
• Female patients with excessive menstrual bleeding or abnormal uterine bleeding should visit the gynecology department.

How is iron deficiency anemia treated?

Treatment includes three aspects: iron supplementation, addressing the cause of iron deficiency, and red blood cell transfusion in critical cases.

• Iron supplementation mainly involves iron medications.
  • Oral iron supplements: For most cases of iron deficiency anemia or iron deficiency without anemia, oral iron supplements are preferred. Organic iron supplements generally have fewer side effects than inorganic ones but are more expensive. Inorganic iron supplements mainly include ferrous sulfate, while organic ones include ferrous succinate, polysaccharide-iron complex, etc.
  • Intravenous iron supplements: These are administered via intravenous infusion. Intravenous iron is considered for patients with continuous blood loss where oral supplementation is insufficient, post-digestive surgery, inflammatory bowel disease, chronic kidney disease, severe side effects from oral iron, poor oral compliance, or unconscious patients.
  • Vitamin C and folic acid: Vitamin C aids iron absorption and utilization; folic acid helps prevent pernicious anemia and supports hemoglobin synthesis. Both can assist iron supplementation.
  • Diet: Foods rich in iron and vitamins can be consumed. However, for iron deficiency anemia patients, diet (including various "supplements") cannot replace iron medications.

• Addressing the cause of iron deficiency: If the deficiency is due to inadequate dietary intake, increase intake; if caused by chronic gastritis from Helicobacter pylori, eradicate the bacteria; if due to abnormal uterine bleeding, further address the underlying cause. If iron deficiency stems from a severe illness, the focus should be on treating that illness.

• Red blood cell transfusion in critical cases: For extremely severe anemia, anemia with severe symptoms, or life-threatening anemia, concentrated red blood cell transfusion is needed; if unavailable, blood transfusion may be performed.

What should I do if I experience side effects from iron supplements?

About 70% of patients taking oral iron supplements experience varying degrees of digestive system side effects, including metallic taste, nausea, vomiting, bloating, abdominal pain, diarrhea, or constipation. If side effects occur, consult a doctor promptly to adjust dosage or administration for better treatment tolerance.

How long does it take for oral iron supplementation to alleviate iron deficiency anemia?

Most patients taking oral iron supplements see an increase in hemoglobin levels within 1–2 weeks, and symptoms like pica (abnormal cravings) improve rapidly. After 4–8 weeks of treatment, hemoglobin levels typically normalize. Patients should continue oral iron supplements for another 4–6 months as prescribed to replenish iron stores.

DIET & LIFESTYLE

Should patients with iron deficiency anemia supplement iron on their own?

There are many supplements on the market containing trace elements such as iron. However, if iron deficiency anemia has been diagnosed, iron supplementation should be done under the guidance of a physician and not self-administered. Using over-the-counter medications to treat anemia on your own may mask the underlying cause of the condition.

Can patients with iron deficiency anemia drink strong tea or coffee?

Strong tea and coffee have a negative impact on iron absorption, so it is recommended that patients with iron deficiency anemia limit their consumption.

PREVENTION

How to Prevent Iron Deficiency Anemia?

• Ensure adequate iron intake in daily diet.
• Seek medical attention promptly if symptoms of iron deficiency anemia appear.
• High-risk groups should follow medical advice for relevant tests.
• Promote breastfeeding and supplement iron-rich foods after 6 months of age as advised. For non-breastfed infants, use age-appropriate formula. Avoid cow's milk before age 1.
• Children and adolescents should maintain a balanced diet and avoid picky eating.
• Pregnant and breastfeeding women should consciously increase iron intake and follow medical advice for screening and folic acid supplementation. Non-anemic pregnant women may take low-dose iron supplements under medical supervision for prevention.