Causes of Iron Deficiency Anemia: Understanding the Key Factors Behind Low Iron Levels
Iron deficiency anemia is one of the most common types of anemia worldwide, affecting millions of people across all age groups. It occurs when the body lacks sufficient iron to produce adequate hemoglobin—the protein in red blood cells responsible for carrying oxygen. Without enough iron, the body can't maintain healthy red blood cell production, leading to fatigue, weakness, and a range of other symptoms. While it may seem like a simple nutritional issue, the underlying causes are often complex and multifaceted.
Inadequate Iron Intake and Increased Physiological Demand
Certain life stages significantly increase the body's need for iron, making individuals more vulnerable to deficiency if dietary intake isn't adjusted accordingly. Infants and young children, for example, experience rapid growth and development, which dramatically raises their iron requirements. If they aren't introduced to iron-rich complementary foods—such as lean meats, eggs, legumes, and fortified cereals—at the appropriate time, they're at high risk of developing iron deficiency.
Adolescents, particularly girls going through puberty, also face increased iron demands due to growth spurts and the onset of menstruation. Poor eating habits, such as extreme dieting or picky eating, can further limit iron consumption, increasing the likelihood of deficiency.
Pregnant and lactating women represent another high-risk group. During pregnancy, blood volume expands significantly, and the developing fetus draws heavily on maternal iron stores. Without proper supplementation or a diet rich in heme iron (found in animal products), expectant mothers are highly susceptible to anemia. Similarly, breastfeeding increases daily iron needs, compounding the challenge of maintaining optimal levels.
Even among adults, lifestyle choices such as long-term vegetarianism or unbalanced diets low in bioavailable iron can contribute to insufficient intake. While plant-based sources like spinach and beans contain iron, it's non-heme iron, which is less efficiently absorbed than the heme iron found in meat, poultry, and fish.
Impaired Iron Absorption in the Digestive Tract
Even with adequate dietary iron, some individuals cannot properly absorb the mineral due to gastrointestinal conditions or medical interventions. Chronic atrophic gastritis, a condition that reduces stomach acid production, impairs the breakdown of food and limits the conversion of iron into its absorbable form.
Patients who have undergone gastric surgery, including partial or total gastrectomy, often struggle with nutrient absorption because the stomach plays a crucial role in preparing iron for uptake in the small intestine. Similarly, malabsorptive disorders such as celiac disease, inflammatory bowel disease (IBD), and intestinal resection can disrupt normal iron absorption pathways.
The Role of Medications in Reducing Iron Uptake
Commonly prescribed medications can also interfere with iron absorption. Proton pump inhibitors (PPIs) and antacids, used to treat acid reflux and peptic ulcers, reduce gastric acidity, which is essential for liberating iron from food. Long-term use of these drugs has been linked to lower serum iron levels and an elevated risk of deficiency.
Additionally, deficiencies in other nutrients—such as vitamin B12 or folate—can mask or exacerbate iron-related issues by altering red blood cell morphology and complicating diagnosis.
Excessive or Chronic Blood Loss: The Leading Cause
By far, chronic blood loss is the most prevalent cause of iron deficiency anemia in adults. Every time blood is lost, iron stored in hemoglobin is depleted. When losses occur repeatedly over time, the body's reserves become exhausted, leading to anemia.
Gastrointestinal Sources of Blood Loss
The digestive tract is a common site of occult (hidden) bleeding. Conditions such as peptic ulcers, hemorrhoids, colonic polyps, and gastric or colorectal cancers can all result in slow, persistent blood loss. Other contributors include esophageal varices, hiatal hernias, and parasitic infections like hookworm, especially in endemic regions.
Because this type of bleeding may not always be visible, patients might remain unaware until symptoms of anemia—such as dizziness, pallor, or shortness of breath—become pronounced.
Gynecological Causes in Women
For premenopausal women, heavy menstrual bleeding (menorrhagia) is a major contributor. Underlying causes include uterine fibroids, endometrial polyps, adenomyosis, and the use of intrauterine devices (IUDs). Hormonal imbalances and certain coagulation disorders can also lead to prolonged or excessive periods.
Other Less Common but Significant Sources
Rare causes of chronic blood loss include recurrent nosebleeds, pulmonary hemorrhage, and hemoglobinuria (the presence of hemoglobin in urine due to red blood cell destruction). Individuals undergoing regular hemodialysis for kidney failure often lose small amounts of blood during treatment sessions.
Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a genetic disorder characterized by abnormal blood vessel formation, leading to frequent bleeding from the nose, gastrointestinal tract, and other organs.
Frequent blood donation without sufficient recovery time between donations can also deplete iron stores, particularly in women and younger donors with already limited reserves.
In summary, iron deficiency anemia arises from a combination of factors including poor intake, impaired absorption, and excessive loss. Recognizing the root cause is essential for effective treatment and long-term management. Early screening, dietary optimization, and medical intervention when necessary can prevent complications and restore quality of life.