What medical issues cause low iron?

September 28, 2025 •

4 min read

Iron deficiency is the most common nutritional deficiency and leading cause of anemia worldwide, but it's not always a simple dietary issue. Beyond diet, understanding what medical issues cause low iron is crucial for effective diagnosis and treatment.

Quick Summary

Low iron can be caused by medical issues including significant blood loss from heavy menstruation, internal bleeding from ulcers or cancer, and conditions like celiac or Crohn's disease that impair iron absorption. Chronic inflammatory diseases can also interfere with the body's iron use.

Key Points

Hidden Bleeding is Common: Chronic, unseen blood loss from the gastrointestinal tract (e.g., ulcers, cancer, NSAID use) or heavy menstruation is a major medical reason for low iron.
Malabsorption is a Key Factor: Conditions like celiac disease and Crohn's disease, or surgery like gastric bypass, prevent the body from absorbing iron effectively, regardless of diet.
Chronic Inflammation Disrupts Iron Use: Persistent inflammation from diseases like rheumatoid arthritis or kidney disease can cause 'functional iron deficiency' by locking iron away in storage.
Diet Isn't Always the Cause: For many, iron deficiency is a symptom of a deeper medical issue, not just a result of poor dietary intake.
Diagnosis Requires Investigation: Identifying the root cause requires more than just blood tests; it may involve looking for hidden bleeding or testing for specific malabsorption disorders.
Treatment Targets the Root Cause: Simply taking supplements may be ineffective if the underlying medical problem is not properly addressed.

Understanding Iron's Role and Medical Causes

Iron is an essential mineral vital for producing hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the rest of the body. When iron levels are too low, the body can't produce enough healthy red blood cells, leading to a condition called iron-deficiency anemia. While dietary intake is a common factor, several underlying medical conditions can significantly impact iron levels, either by causing blood loss, hindering absorption, or disrupting its use in the body.

Hidden Blood Loss: The Primary Culprit

Losing blood means losing iron, and sometimes this loss is not obvious. Chronic, low-level bleeding can deplete iron stores over time without any visible signs.

Gastrointestinal (GI) Bleeding: This is a leading cause, especially in men and postmenopausal women. It can result from a variety of GI conditions:
- Peptic ulcers: Sores in the stomach or small intestine can bleed slowly.
- Chronic use of NSAIDs: Regular use of medications like aspirin or ibuprofen can cause stomach irritation and internal bleeding.
- Colorectal cancer or polyps: These growths can cause occult (hidden) blood loss in the stool.
- Inflammatory bowel disease (IBD): Conditions like Crohn's disease and ulcerative colitis can lead to inflammation and bleeding in the digestive tract.
Heavy Menstrual Bleeding: For premenopausal women, excessive or prolonged bleeding during periods is a very common cause of iron deficiency.
Urinary Tract Bleeding: Less common, but chronic bleeding from the kidneys or bladder can lead to iron loss.
Frequent Blood Donation: Regular blood donations can deplete iron stores over time if not adequately replaced through diet or supplementation.

Malabsorption Disorders: Preventing Iron Uptake

Even with sufficient iron intake, certain medical conditions can prevent the small intestine from properly absorbing the mineral.

Celiac Disease: This autoimmune disorder damages the lining of the small intestine in response to gluten, significantly hindering nutrient absorption, including iron. Even after adopting a gluten-free diet, a person may still need iron supplementation to correct long-term deficiencies.
Gastric Bypass Surgery: Procedures that bypass parts of the small intestine, where much of the iron is absorbed, can lead to chronic malabsorption. This requires lifelong monitoring and supplementation.
H. pylori Infection: Chronic infection with this stomach bacteria can cause gastritis and bleeding, while also interfering with the stomach's ability to produce acid needed for iron absorption.

Chronic Diseases and Inflammation

Long-term health conditions can interfere with the body's iron regulation, even if diet and absorption are normal. This is known as anemia of chronic disease.

Chronic Kidney Disease: The kidneys produce a hormone called erythropoietin, which signals the bone marrow to produce red blood cells. In chronic kidney disease, insufficient erythropoietin is produced, leading to anemia. Inflammation associated with the disease also prevents the body from effectively utilizing available iron.
Autoimmune Diseases: Conditions such as rheumatoid arthritis, lupus, and inflammatory bowel diseases involve chronic inflammation. This inflammation leads to increased levels of a protein called hepcidin, which blocks iron absorption and prevents its release from storage.
Heart Failure and Obesity: Similar to autoimmune conditions, these and other long-lasting inflammatory diseases can cause functional iron deficiency, where iron is present but locked away and unavailable for red blood cell production.

How Different Causes Impact Iron Levels


Feature	Dietary Insufficiency	Chronic Blood Loss	Malabsorption Disorders	Anemia of Chronic Disease
Cause	Insufficient dietary iron intake	Slow, persistent bleeding	Inability to absorb iron from food	Chronic inflammation disrupts iron use
Symptom Onset	Gradual, often over years	Gradual, may show no visible signs	Gradual, may have GI symptoms	Gradual, alongside other chronic illness symptoms
Ferritin Level	Low	Low	Low	Normal to high
Diagnosis	Dietary history, blood tests	Fecal occult blood test, endoscopy	Celiac panel, intestinal biopsy	Blood tests, markers of inflammation
Treatment	Iron-rich foods, supplements	Find and treat bleeding source	Treat underlying condition, special supplements	Manage chronic disease, iron therapy

Other Contributing Factors and Diagnosis

Beyond the major categories, other medical factors can influence iron status. For example, certain rare inherited conditions can cause problems with iron handling. The key for anyone with persistent low iron levels is a thorough medical evaluation to uncover the root cause. This may include blood tests beyond a simple iron panel, such as a fecal occult blood test to check for hidden blood, or more advanced procedures like an endoscopy or colonoscopy. A hematologist or gastroenterologist may be consulted to help identify the specific issue.

For more in-depth information on gastrointestinal disorders, consult authoritative resources like the National Institute of Diabetes and Digestive and Kidney Diseases [^1].

What Comes Next: The Path to Recovery

Once the medical issue causing low iron is identified, a healthcare provider can formulate a specific treatment plan. In many cases, simply taking iron supplements is not enough if the underlying problem, such as hidden bleeding or poor absorption, is not addressed. Treating the root cause is paramount to achieving long-term iron repletion and alleviating the symptoms of iron deficiency anemia.

Frequently Asked Questions

Yes, heavy menstrual bleeding is one of the most common medical causes of low iron, especially in premenopausal women. Consistent loss of blood and, therefore, iron, can lead to deficiency over time. This is often an underappreciated cause of anemia.

Stomach and intestinal issues can cause low iron in two main ways: bleeding and malabsorption. Chronic bleeding from ulcers or inflammation can cause slow, steady blood loss. Conditions like celiac disease or gastric surgery can prevent the body from properly absorbing iron from food.

Chronic illnesses like kidney disease, autoimmune disorders (e.g., rheumatoid arthritis), and heart failure cause chronic inflammation. This inflammation disrupts the body's iron regulation, leading to a condition called 'anemia of chronic disease,' where iron is present but inaccessible for red blood cell production.

If initial tests don't reveal a clear cause like hidden bleeding or malabsorption, further investigation by a specialist, such as a gastroenterologist or hematologist, may be needed. They can perform more detailed procedures to find a less common underlying issue.

Yes. Chronic use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen can cause bleeding in the stomach, leading to iron loss. Other medications that reduce stomach acid, such as proton pump inhibitors, can also interfere with iron absorption.

Diagnosis starts with a full blood panel. If iron deficiency is confirmed, a doctor will likely perform additional tests based on your symptoms and medical history. This might include a fecal occult blood test, endoscopy, or colonoscopy to check for GI bleeding, or a celiac disease panel.

Yes, bariatric surgery, particularly gastric bypass procedures, is a known cause of long-term iron deficiency. By altering the digestive system, it can bypass the sections of the small intestine where most iron is absorbed, requiring lifelong supplementation and monitoring.