What is the most common cause of iron deficiency anaemia?

According to the World Health Organization, iron deficiency is the most common nutritional deficiency worldwide. In many adults, a significant underlying factor leading to iron deficiency anaemia is blood loss. Understanding this primary cause is crucial for accurate diagnosis and effective treatment strategies.

Quick Summary

Chronic blood loss is the single most common cause of iron deficiency anaemia in adults, with the source varying by demographic. For premenopausal women, heavy menstrual bleeding is a frequent culprit, while for men and postmenopausal women, gastrointestinal bleeding is the most likely reason.

Key Points

• Chronic Blood Loss: The most common cause of iron deficiency anaemia in adults is long-term blood loss, not just dietary inadequacy.

• Heavy Menstruation: Premenopausal women should consider heavy periods as a primary suspect for their iron deficiency.

• GI Bleeding: In men and postmenopausal women, the most likely cause is bleeding from the gastrointestinal tract, which can be a sign of a serious underlying condition.

• Underlying Cause: It is crucial to determine the cause of the blood loss and not just treat the resulting anaemia with iron supplements alone.

• Diverse Causes: Beyond blood loss, factors like impaired absorption (e.g., celiac disease) and increased demand (e.g., pregnancy) can also lead to iron deficiency.

• Professional Diagnosis: A proper diagnosis from a healthcare provider is essential, as the symptoms of iron deficiency anaemia are often non-specific and can overlap with other conditions.

The Primary Culprit: Blood Loss

While an inadequate dietary intake of iron can contribute to the condition, the single most common and often overlooked cause of iron deficiency anaemia in adults is chronic, long-term blood loss. The source and nature of this blood loss differ significantly based on age, gender, and underlying medical conditions.

Menstrual Bleeding in Women

For premenopausal women, heavy menstrual bleeding is a very common cause of chronic blood loss, and by extension, iron deficiency anaemia. The monthly loss of blood can deplete the body's iron stores over time, especially if their dietary intake is not sufficient to compensate. In many cases, women with heavy periods may not even realize the extent of their blood loss or that it is the root cause of their fatigue and other symptoms. Addressing the menstrual issue is a vital part of the overall treatment plan.

Gastrointestinal (GI) Bleeding in Adults

For men and postmenopausal women, gastrointestinal bleeding is the most common cause of iron deficiency anaemia. This bleeding can be subtle and slow, often going unnoticed by the individual. Sources of GI bleeding can include:

• Peptic ulcers: Sores in the lining of the stomach or duodenum that can bleed slowly over time.
• Polyps in the colon: Small growths that can bleed, and may sometimes be an early sign of colorectal cancer.
• Colorectal cancer: Chronic, slow bleeding is a classic symptom of this serious condition, particularly in middle-aged and older adults.
• Regular use of certain medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or aspirin can cause stomach irritation and bleeding.
• Other GI disorders: Conditions such as celiac disease and inflammatory bowel disease (IBD) can also lead to impaired iron absorption and blood loss.

Other Forms of Chronic Blood Loss

Less common but still significant causes of blood loss include:

• Frequent blood donation, which can lower iron reserves.
• Urinary tract bleeding.
• Traumatic injuries or surgery involving blood loss.

Factors Beyond Blood Loss

While blood loss is the most prevalent cause in adults, other factors play a significant role in developing iron deficiency anaemia.

Dietary Inadequacy

Though less common as a sole cause in developed countries, not consuming enough iron-rich foods can be a contributing factor, especially for certain populations. This is particularly true for infants, children, vegetarians, and vegans who do not consume fortified foods or iron supplements. The body absorbs iron most effectively from meat (heme iron), but plant-based sources (non-heme iron) can also be used, especially when consumed with vitamin C to enhance absorption.

Impaired Iron Absorption

Sometimes, even with sufficient dietary iron, the body cannot absorb it properly. This can be caused by several conditions:

• Celiac disease: The small intestine lining is damaged by gluten, impairing its ability to absorb iron.
• Gastric bypass surgery: The surgical rerouting of the digestive system can bypass the parts of the intestine where most iron absorption occurs.
• Chronic inflammation: Conditions like kidney disease, inflammatory bowel disease, or autoimmune diseases can interfere with the body's ability to regulate and use iron.
• H. pylori infection: This bacterial infection in the stomach can also contribute to malabsorption.

Increased Demand for Iron

• Pregnancy: The body's blood volume increases during pregnancy, and iron is required for both the mother and the developing fetus.
• Growth spurts: Infants and young children experience periods of rapid growth that increase their need for iron.

Diagnosing the Root Cause

Because there are multiple potential causes, a healthcare provider will perform several tests to diagnose iron deficiency anaemia and determine its origin. This typically includes a Complete Blood Count (CBC) and a ferritin level test. For men and postmenopausal women, further investigation to rule out gastrointestinal bleeding is standard practice.

The Path to Recovery

Treating iron deficiency anaemia involves both addressing the underlying cause and replenishing the body's iron stores. Treatment options include:

• Oral iron supplements: The most common form of treatment, often taken for several months.
• Intravenous (IV) iron: May be necessary for individuals who cannot tolerate or absorb oral supplements, or those with severe anaemia.
• Addressing the source of blood loss: For example, managing heavy menstrual bleeding or treating GI issues.

Comparison of Common Causes

Cause	Primary Affected Group	Key Characteristics	Diagnostic Approach
Menstrual Bleeding	Premenopausal women	Often underestimated, chronic blood loss	History, hemoglobin/ferritin test
GI Bleeding	Men, postmenopausal women	Subtle, slow, often painless blood loss	Endoscopy, colonoscopy, fecal occult blood test
Malabsorption	Post-surgery patients, celiac patients	Impaired nutrient absorption, sometimes weight loss	Blood tests, GI evaluation
Inadequate Diet	Infants, vegetarians/vegans, low-income	Lack of iron-rich food, insufficient supplements	Dietary history, blood tests

Conclusion

While a variety of factors can contribute to low iron, the most common cause of iron deficiency anaemia is chronic blood loss. The specific source of bleeding—whether from heavy menstruation, the gastrointestinal tract, or another issue—varies across demographics. For this reason, it is critical to not simply treat the symptoms with supplements, but to identify and address the root cause with a healthcare professional to ensure a complete and lasting recovery. For more detailed information on blood disorders, consult an authoritative source like the National Heart, Lung, and Blood Institute (NHLBI) at https://www.nhlbi.nih.gov/health/anemia/iron-deficiency-anemia.

Frequently Asked Questions

What is the most common cause of iron deficiency anaemia in premenopausal women?

For premenopausal women, the most common cause is heavy menstrual bleeding. The monthly blood loss can gradually deplete the body's iron stores, leading to anaemia over time.

What causes iron deficiency anaemia in men and postmenopausal women?

In these groups, the most common cause is chronic, slow bleeding from the gastrointestinal tract. This can stem from conditions like ulcers, polyps, or, in some cases, cancer.

Is poor diet the most common cause of iron deficiency anaemia?

While inadequate dietary iron intake can be a factor, especially in infants, children, or those on restrictive diets, chronic blood loss is the most common cause of iron deficiency anaemia in adults.

How does gastrointestinal bleeding cause iron deficiency?

Slow, consistent bleeding in the stomach or intestines can lead to the gradual loss of red blood cells and the iron they contain. This often goes unnoticed until anaemia develops and is diagnosed through tests.

Can pregnancy lead to iron deficiency anaemia?

Yes, pregnancy significantly increases the body's demand for iron due to higher blood volume and the needs of the fetus. If iron intake isn't increased, it can lead to deficiency and anaemia.

What is malabsorption and how does it cause iron deficiency anaemia?

Malabsorption refers to a condition where the small intestine cannot properly absorb nutrients, including iron. This can be caused by conditions like celiac disease or certain types of bariatric surgery.

Why is it important to find the underlying cause of iron deficiency anaemia?

Treating iron deficiency with supplements is only a temporary fix if the underlying cause, especially chronic bleeding, is not addressed. Finding the root cause is crucial for a complete recovery and to rule out serious conditions.