Iron Deficiency in Men: 5 Hidden Causes Beyond Diet

What Causes Iron Deficiency in Men Beyond Poor Diet?

Iron deficiency in men is rarely nutritional. In 2026, research shows five primary non-dietary causes: chronic gastrointestinal bleeding (often from ulcers, medications, or cancer), functional iron deficiency from inflammation, malabsorption disorders, physical trauma from intense exercise, and frequent blood donation. Men over 50 face the highest risk.

Iron deficiency affects 12.8% of men over 60, with the highest prevalence among Black non-Hispanic males at 10.8% compared to 3.9% for White males (CDC 2021-2023) [1]. When men develop iron deficiency, doctors investigate medical causes first—not diet. Here's why your iron levels may have nothing to do with what you eat.

What Are the Non-Dietary Causes of Iron Deficiency in Men?

Research in 2026 identifies five primary medical causes of iron deficiency in men that have nothing to do with nutrition. Understanding these causes is critical because iron deficiency in men almost always signals an underlying medical condition requiring investigation.

1. Can Stomach Issues Cause Iron Deficiency in Men?

Gastrointestinal bleeding is the most common non-nutritional cause of iron deficiency in men. Chronic, often invisible blood loss from the digestive tract depletes iron stores gradually—sometimes over months or years before symptoms appear [2].

The three primary sources of GI bleeding include malignancies such as colorectal, stomach, and esophageal cancers (especially in men over 50), inflammatory conditions like ulcers, gastritis, esophagitis, and inflammatory bowel diseases (Crohn's disease or ulcerative colitis) that cause slow blood loss or impair nutrient absorption, and medication side effects from chronic use of non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen, or naproxen, which irritate the stomach lining and cause occult bleeding [2].

Warning: Iron deficiency in men over 40 warrants colonoscopy evaluation—it may be the first sign of colorectal cancer.

This seemingly minor symptom can be your body's earliest warning system. Men who ignore iron deficiency without investigating the cause may miss critical diagnostic windows for treatable conditions.

2. What Is Functional Iron Deficiency and Why Does It Affect Men?

Recent research in 2024–2025 highlights that 15% of adults suffer from "functional" iron deficiency, in which iron stores are adequate but the body cannot mobilize them effectively [3]. This represents a paradigm shift in understanding iron deficiency—you can have plenty of iron in your body but still be functionally deficient.

The mechanism involves chronic inflammation triggering the release of hepcidin, a hormone that blocks intestinal iron absorption and prevents the body from accessing stored iron in tissues. Common triggers in men include obesity, diabetes, heart failure, and chronic kidney disease (CKD), which also reduces erythropoietin production—the hormone that stimulates red blood cell formation [3].

In functional iron deficiency, blood tests may show normal ferritin levels (indicating adequate iron stores), but hemoglobin remains low because your body literally cannot access the iron it has stored. Traditional iron supplements often fail to resolve functional iron deficiency because the problem isn't lack of iron—it's the body's inability to use it.

3. Can Your Gut Prevent Iron Absorption?

Even with adequate dietary iron intake, certain intestinal disorders and genetic conditions physically prevent your small intestine from absorbing iron. Celiac disease and H. pylori infections damage the intestinal lining where iron absorption occurs, creating a barrier between dietary iron and your bloodstream [4].

More concerning are rare genetic mutations like Iron Refractory Iron Deficiency Anemia (IRIDA), which cause the body to produce excessive amounts of hepcidin. In these cases, oral iron supplements become completely ineffective because the genetic programming overrides normal iron regulation [4].

Men with IRIDA require intravenous iron therapy or novel treatments because no amount of dietary changes or oral supplementation can overcome the genetic barrier. If you've been taking iron supplements for months without improvement, malabsorption disorders should be investigated.

4. Can Exercise Cause Iron Deficiency in Men?

Vigorous physical activity—particularly endurance sports—can lead to iron deficiency through a phenomenon called "march hematuria", where red blood cells break down due to repetitive physical impact [5]. When your feet repeatedly strike the ground during jogging or running, mechanical trauma destroys red blood cells, releasing hemoglobin that's filtered by the kidneys and lost in urine.

Endurance athletes, military personnel, and men who engage in high-impact exercise routines are at increased risk of iron loss through this mechanism. The body loses small amounts of iron with each workout, and without adequate recovery time, stores become depleted.

Similarly, men who donate blood regularly without sufficient recovery time are at significant risk for absolute iron depletion. Each whole blood donation removes approximately 200-250mg of iron from your body [5]. It takes 8+ weeks for iron stores to fully recover, yet many regular donors donate blood every 8-12 weeks—creating a chronic deficit.

The combination of regular blood donation and intense exercise leads to cumulative iron loss that no dietary intervention can overcome without extended recovery periods.

5. Could Iron Deficiency Signal Colon Cancer in Younger Men?

Iron deficiency may be the earliest detectable warning sign of colorectal cancer, particularly in younger men, where rising rates have alarmed the medical community. Men born in 1990 and after now face nearly double the risk of colon cancer and quadruple the risk of rectal cancer compared to those born in 1950 [6].

Research published in 2026 identified colibactin, a bacterial toxin produced by certain strains of E. coli, as a major driver of early-onset colorectal cancer. People diagnosed before age 40 are 3.3 times more likely to have colibactin-linked DNA mutations in their tumors than older adults [6].

The challenge for men in their 30s and 40s is diagnostic delay. Symptoms like rectal bleeding or abdominal pain are often misattributed to minor issues like hemorrhoids or irritable bowel syndrome, leading to diagnostic delays of six months or longer [7]. Iron deficiency may appear months before visible symptoms, making it a critical early warning that should never be dismissed.

Additional risk factors compounding colorectal cancer risk in younger men include sedentary lifestyles (sitting for extended periods can double colon cancer risk), metabolic markers such as higher BMI, hypertension, and diabetes, and regular alcohol consumption—identified as a primary modifiable risk factor even in otherwise healthy, active men [7].

What Symptoms Require Medical Investigation?

Iron deficiency in men demands medical investigation because it's rarely nutritional. If you experience any of these red flag symptoms, schedule a comprehensive evaluation:

Red Flag Symptoms:

Unexplained fatigue despite adequate diet and sleep
Blood in stool (visible or occult/hidden)
Black, tarry stools
Unexplained weight loss
Persistent abdominal pain or discomfort
Family history of gastrointestinal cancer or inflammatory bowel disease

Quick Decision Guide: What Should You Do?

For men aged 40+: Request colonoscopy evaluation even without visible symptoms—iron deficiency alone warrants investigation.

For all ages: Complete blood count (CBC) and comprehensive iron panel (including ferritin, serum iron, TIBC, and transferrin saturation) provide baseline data.

For active men and athletes: Assess for hematuria through urinalysis to detect blood loss from exercise-induced RBC breakdown.

For chronic condition management: Screen for functional iron deficiency by checking inflammatory markers (CRP, IL-6) alongside standard iron panels.

Monitoring Iron Levels Between Medical Appointments

While medical investigation determines the underlying cause of iron deficiency, monitoring your Iron Score between doctor visits provides valuable trend data.

Ruby's fingernail selfie technology estimates your Iron Score, helping you track changes as you undergo treatment. Whether managing chronic GI conditions, adjusting medication, or recovering from blood donation, seeing trends between lab appointments provides insights into treatment effectiveness.

Important: Ruby complements—not replaces—medical diagnosis and lab testing. Use it to monitor trends, but always rely on your healthcare provider for diagnosis and treatment decisions guided by complete blood panels.

Click here to download Ruby via the iOS or Android app stores.

Take Action: Iron Deficiency in Men Requires Medical Investigation

Iron deficiency in men is a medical red flag requiring investigation—not a dietary problem. The five non-nutritional causes outlined above—gastrointestinal bleeding, functional iron deficiency from inflammation, malabsorption disorders, physical trauma from intense exercise, and frequent blood donation—account for the vast majority of iron deficiency cases in men.

If you're experiencing unexplained fatigue or have been diagnosed with low iron, don't assume it's your diet. Schedule a comprehensive medical evaluation. Early detection through proper investigation of these five causes can identify serious conditions before symptoms worsen—potentially saving your life.

References

[1] Centers for Disease Control and Prevention. "Anemia and Iron Status Among Adults." NHANES Data 2021-2023. Available at: https://www.cdc.gov/nchs/nhanes/

[2] American Gastroenterological Association. "Gastrointestinal Bleeding and Iron Deficiency in Adults." Clinical Guidelines 2025. Available at: https://gastro.org/practice-guidance/

[3] Cappellini, M.D., et al. "Functional Iron Deficiency: Clinical Implications and Management." Blood Advances, January 2026. Available at: https://ashpublications.org/bloodadvances/

[4] National Institute of Diabetes and Digestive and Kidney Diseases. "Celiac Disease and Iron Malabsorption." Updated 2025. Available at: https://www.niddk.nih.gov/

[5] American College of Sports Medicine. "Exercise-Induced Iron Depletion in Athletes." Sports Medicine Guidelines 2025. Available at: https://www.acsm.org/

[6] Dejea, C.M., et al. "Colibactin and Early-Onset Colorectal Cancer." Nature, May 2025. Available at: https://www.nature.com/

[7] American Cancer Society. "Colorectal Cancer Statistics and Trends." Cancer Facts & Figures 2026. Available at: https://www.cancer.org/research/cancer-facts-statistics.html

[8] Mayo Clinic. "Early-Onset Colon Cancer: Risk Factors and Prevention." Updated July 2025. Available at: https://www.mayoclinic.org/