Why can't I keep my iron levels up? Understanding the underlying causes

October 28, 2025 •

5 min read

Iron deficiency is the world's most common nutrient deficiency, affecting over 25% of the global population. If you find yourself repeatedly asking, "Why can't I keep my iron levels up?", it’s a sign that simply increasing your intake may not be enough to fix the problem. The issue often lies deeper, involving complex interactions with your diet, gut health, and body's regulatory systems.

Quick Summary

Several factors, including diet, absorption issues, chronic inflammation, and underlying medical conditions, can cause persistent low iron. Effective strategies require identifying the root cause, adjusting dietary habits, and optimizing your supplement routine to help maintain healthy iron stores over the long term.

Key Points

Absorption Issues: Gastrointestinal conditions like celiac disease, IBD, or low stomach acid can severely hinder iron absorption from food and supplements.
Chronic Inflammation: Elevated hepcidin, a hormone produced during chronic inflammation, traps iron in the body and prevents it from being used, a condition known as anemia of chronic disease.
Hidden Blood Loss: Ongoing blood loss from heavy periods or internal sources like ulcers can deplete iron faster than it can be replaced.
Dietary Interference: Consuming coffee, tea, or calcium near meals or supplements can block iron absorption. Phytates in whole grains and legumes also interfere.
Optimized Supplementation: Trying alternate-day dosing or different iron formulations (like ferrous bisglycinate) can improve absorption and reduce side effects.
Medical Investigation: For persistent low iron, it is crucial to work with a doctor to diagnose and treat any underlying medical conditions causing the issue.
IV Iron Therapy: In cases of severe malabsorption or chronic disease, intravenous iron may be the only effective solution to replenish iron stores.

Causes of Persistently Low Iron Levels

For many, correcting low iron is as simple as taking a daily supplement. However, if your levels rebound and then quickly dip again, a more complex issue is likely at play. Understanding these root causes is crucial for effective treatment.

Ineffective Iron Absorption

Your body's ability to absorb iron is a delicate process, primarily occurring in the small intestine. Problems in this area can significantly hinder your efforts to raise iron levels.

Gastrointestinal Conditions: Chronic digestive disorders like celiac disease, inflammatory bowel disease (Crohn's or ulcerative colitis), and H. pylori infections can cause inflammation and damage the gut lining, impairing nutrient uptake.
Reduced Stomach Acid: Stomach acid is vital for converting dietary iron into a form your body can absorb. Factors like aging, chronic stress, and long-term use of acid-blocking medications (e.g., PPIs, antacids) can lead to low stomach acid (hypochlorhydria), hindering this conversion.
Gastric Surgery: Bariatric procedures like gastric bypass intentionally alter the digestive tract. This can cause iron deficiency by bypassing the duodenum and jejunum, the key sites of iron absorption, and reducing stomach acid production.

The Role of Chronic Inflammation and Hepcidin

Chronic inflammation is a significant, often overlooked, cause of persistent low iron. This is regulated by a hormone called hepcidin, which controls iron absorption and distribution.

Anemia of Chronic Disease (ACD): In cases of chronic inflammation or infection, the body produces excess hepcidin. High hepcidin levels reduce the release of iron from storage and decrease intestinal iron absorption, essentially trapping it in the body and restricting its availability for red blood cell production.
Associated Conditions: This occurs in various inflammatory states, including autoimmune diseases (like rheumatoid arthritis), chronic kidney disease (CKD), and heart failure.

Chronic and Hidden Blood Loss

Your body can't maintain iron stores if it's losing blood faster than it can replace it. Sometimes this bleeding is obvious, but often it goes unnoticed.

Heavy Menstrual Periods: For premenopausal women, heavy or prolonged menstrual bleeding is a very common cause of ongoing iron loss.
Gastrointestinal Bleeding: Conditions such as ulcers, gastritis, hemorrhoids, or bleeding from a polyp can cause slow, chronic blood loss that is not visible in stool. Regular use of NSAIDs can also irritate the stomach and increase this risk.
Frequent Blood Donation: While a noble act, frequent blood donation can significantly deplete iron stores, especially if your intake isn't sufficient to compensate.

Dietary Factors and Inhibitors

What you eat and drink can either enhance or inhibit iron absorption. Consuming inhibitors at the same time as iron-rich foods or supplements can severely impact your body's ability to use that iron.

Tea and Coffee: The tannins and polyphenols in tea and coffee are potent inhibitors of non-heme iron absorption. Drinking these beverages with meals can significantly reduce iron uptake.
Calcium-Rich Foods and Supplements: Calcium can interfere with the absorption of both heme and non-heme iron. It is best to avoid taking calcium supplements or dairy products at the same time as your iron supplement.
Phytates: Found in high concentrations in whole grains, cereals, legumes, and nuts, phytates can bind to iron and hinder its absorption. Soaking or sprouting these foods can help reduce phytate levels.

Heme vs. Non-Heme Iron: A Comparison

Your body absorbs different types of iron with varying efficiency. Understanding the difference is key to optimizing your dietary intake.


Feature	Heme Iron	Non-Heme Iron
Source	Animal-based foods (red meat, poultry, fish)	Plant-based foods (beans, lentils, spinach, nuts) and fortified foods
Absorption Rate	High (15–35%)	Low (2–20%)
Influencers	Absorption is less affected by dietary factors.	Absorption is strongly inhibited by phytates, polyphenols, and calcium.
Effectiveness	Highly effective for boosting iron levels.	Can be effective, but requires careful meal planning to maximize absorption.

Strategies to Improve and Maintain Iron Levels

If you're struggling to keep your iron levels up, a comprehensive strategy is needed that goes beyond just taking a pill.

Optimize Your Dietary Intake

Pair iron with Vitamin C: Vitamin C dramatically enhances the absorption of non-heme iron. Try squeezing lemon juice over a spinach salad or having orange juice with an iron-fortified cereal.
Cook with cast-iron cookware: For individuals with mild deficiency, cooking acidic foods like tomato sauce in cast-iron pots and pans can leach small amounts of iron into your meal.
Eat heme iron sources: Incorporating lean red meat, poultry, or fish into your diet several times a week is one of the most effective ways to boost iron levels due to the high bioavailability of heme iron.

Refine Your Supplement Strategy

Consider alternate-day dosing: Some studies suggest that taking oral iron supplements every other day may improve absorption and reduce gastrointestinal side effects compared to daily dosing. This is because high daily doses can spike hepcidin levels, which then inhibit further absorption.
Switch to a gentler form: If ferrous sulfate causes side effects like constipation or nausea, a different formulation like ferrous bisglycinate or a liquid iron might be better tolerated and absorbed.

Address the Underlying Medical Cause

Get a proper diagnosis: A doctor can run tests to determine if a condition like celiac disease, IBD, or H. pylori is impairing your absorption. Treating the root cause is necessary for long-term success.
Discuss medications: If you are on a medication that affects stomach acid or causes internal bleeding, consult your doctor about alternatives or mitigation strategies.

When Oral Supplements Aren't Enough

If you have been diligently taking oral supplements and addressing dietary issues but your iron levels remain low, your doctor may recommend intravenous (IV) iron therapy. This delivers iron directly into your bloodstream, bypassing any absorption issues in the gut. This is often necessary for those with severe malabsorption or anemia of chronic disease.

For more detailed information on iron deficiency, consult a trusted resource like the National Heart, Lung, and Blood Institute.

Conclusion

If you can't keep your iron levels up, it's a sign that your body's iron metabolism is facing challenges beyond simple dietary intake. The issue may stem from poor absorption due to a gut condition or low stomach acid, chronic inflammation that elevates hepcidin, or ongoing internal blood loss. By working with a healthcare provider to identify the specific root cause and implementing targeted strategies—whether adjusting your diet, refining your supplement routine, or addressing underlying medical conditions—you can take control of your iron health and move toward lasting resolution.

Frequently Asked Questions

Poor iron absorption can result from several issues, including underlying gastrointestinal diseases like celiac or IBD, low stomach acid, and prior bariatric surgery. These conditions can damage the intestinal lining or alter the digestive environment needed for iron uptake.

Yes, even with a diet high in iron, your levels can be low. This is often due to poor absorption or the presence of dietary inhibitors like tea, coffee, and calcium that block the iron you consume.

Hepcidin is a hormone that regulates iron absorption. When you have a chronic inflammatory condition, hepcidin levels can rise, causing iron to be trapped within cells and limiting its availability for the rest of the body. This is a common cause of low iron in chronically ill patients.

For best results, take iron supplements on an empty stomach with a source of Vitamin C, like a glass of orange juice. Avoid taking them with high-calcium foods, coffee, or tea. Alternate-day dosing may also be more effective for some individuals.

Signs of poor iron absorption often mirror the symptoms of low iron itself, including persistent fatigue, weakness, pale skin, and shortness of breath. If your iron levels do not improve despite consistent supplementation, it's a key indicator of an absorption problem.

IV iron may be necessary if oral supplements are ineffective due to severe malabsorption, significant gut inflammation, or severe anemia of chronic disease. It is a more direct way to replenish iron stores, bypassing digestive issues entirely.

Yes, intense or frequent exercise, particularly endurance training like jogging, can sometimes lead to increased iron loss. This can be caused by micro-injuries that result in small amounts of blood loss, known as 'march hematuria'.

Several medical conditions can cause chronic iron deficiency, including autoimmune disorders, inflammatory bowel disease, chronic kidney disease, and certain cancers. Genetic conditions that affect iron metabolism are also a possibility.

While some may feel better within a few weeks, it typically takes several months of consistent supplementation to fully replenish iron reserves. A doctor will usually recheck blood levels after a few months to monitor progress.

Yes, on average, vegetarians and vegans tend to have lower iron stores than omnivores. This is because they consume only non-heme iron, which is less efficiently absorbed. Strategic pairing of non-heme sources with Vitamin C is essential.