If you’re repeatedly struggling with low iron, ferritin that never rises, fatigue that won’t lift with supplements, or iron labs that simply refuse to normalize, you’re certainly not in this battle alone. Iron is reportedly the most common nutritional deficiency and most common cause of anemia among an estimated 2 billion people around the world.
Many people assume that iron deficiency is just about“eating more iron-rich foods,” but clinical research is much more complex. In fact, non-dietary factors, especially issues with absorption and inflammation are sometimes the root cause of chronic iron depletion.
Diet is Not Always the Problem
Sure, what you eat matters, and insufficient iron intake can contribute to low iron levels. In the U.S., fortified foods and varied diets mean severe dietary iron deficiency alone is relatively uncommon compared with other contributors. Heme iron from animal products (meat, poultry, fish) is absorbed more efficiently than non-heme iron from plant sources, and those relying primarily on plant-based iron need careful meal planning to ensure adequate absorption.
But many people eating iron-rich diets still struggle with low iron, a clue that something else is preventing the body from using what’s available.
- Your Gut Might Be Preventing Iron Absorption
Iron is absorbed primarily in the upper small intestine, especially the duodenum. Any condition that damages or alters that part of the gut can reduce iron uptake even if your dietary intake is fine.
Celiac Disease and Malabsorption
Celiac disease, an autoimmune condition triggered by gluten, can cause chronic inflammation and damage to the intestinal lining where iron is absorbed.
- Villous atrophy (flattening of the absorptive surface) reduces the gut’s ability to take up iron from food.
- Even on a gluten-free diet, some people continue to have iron deficiency because the mucosa doesn’t fully heal or ongoing inflammation keeps iron locked away.
- Inflammatory cytokines can raise hepcidin (a hormone that blocks iron absorption and release), worsening deficiency.
Other Malabsorption Causes
Beyond celiac disease, several gut-related issues can hinder iron uptake:
- Inflammatory bowel disease (IBD) such as Crohn’s or ulcerative colitis.
- H. pylori infection, which can disrupt stomach lining and acid balance.
- Low stomach acid production (especially with age or use of acid-blocking medications) can impede iron release from foods before it even reaches absorptive sites.
If your iron doesn’t improve with diet and supplements, exploring absorption with specialized testing is key.
- Chronic Inflammation Locks Iron Away
Even when iron intake is adequate and gut absorption seems intact, chronic inflammation can create what’s known as anemia of chronic disease (ACD), a situation where iron is present in the body but not effectively used.
Inflammation triggers the liver to ramp up production of hepcidin, a hormone that blocks iron from entering the bloodstream and being used by bone marrow for red blood cell synthesis. This is a survival mechanism during infection (to limit iron available to pathogens) but can backfire in long-term inflammatory conditions.
Chronic inflammation linked to conditions like:
- Rheumatoid arthritis
- Lupus
- Chronic infections (example, HIV)
- Cancer
- Chronic kidney disease
…can all cause elevated hepcidin levels, meaning neither iron from diet nor supplements is efficiently absorbed or mobilized. Unlike classic iron deficiency where ferritin is low, inflammation-related iron deficiency may show normal or even elevated ferritin despite poor iron availability, a common clinical pitfall.
- Hidden or Slow Blood Loss Is More Common Than You Think
One of the most overlooked explanations for chronic low iron is blood loss you don’t feel or see. Blood contains iron, and even small amounts of ongoing bleeding can deplete iron stores over time because your body loses iron faster than it can replace it.
Occult Gastrointestinal Bleeding
Conditions that cause slow bleeding inside the digestive tract may fly under the radar:
- Peptic ulcers
- Hemorrhoids
- Colonic polyps
- Cancers of the digestive system
- Long-term use of NSAIDs (like aspirin or ibuprofen)
Many of these sources don’t produce obvious symptoms like visible blood in stool, yet over weeks or months they can strip the body of iron. This is especially relevant in older adults and men, for whom diet alone rarely explains anemia.
Gynecological Blood Loss
In women of reproductive age, heavy menstrual bleeding is a well-known cause of iron loss. However, even periods that feel “normal” to you can be heavier than your body can compensate for over time, especially if spacing between meals and iron intake isn’t optimal.
- Increased Iron Needs
Sometimes your body simply needs more iron than usual and normal dietary intake can’t keep up.
This is seen in:
- Pregnancy, where expanding blood volume and fetal needs increase iron demand.
- Rapid growth phases in adolescents.
- Frequent blood donors, where repeated donation depletes iron stores faster than they recover.
Even when diet seems sufficient, these physiological demands can exceed intake and absorption unless iron is specifically increased.
- Medications and Lifestyle Factors Can Interfere
Iron metabolism isn’t isolated; other medications and habits can influence how much iron your body retains.
- Acid-blocking medications (proton pump inhibitors) reduce stomach acid, which is necessary for iron release from food before absorption.
- Calcium supplements and dairy taken with iron sources can inhibit iron uptake.
- Tea and coffee contain tannins, which also impair absorption when consumed with meals.
Lifestyle alone seldom explains persistent deficiency, but it can tip the balance when other subtle causes are present.
- Genetic or Rare Conditions (Uncommon but Real)
A small subset of people have genetic conditions that affect iron metabolism:
- Iron refractory iron deficiency anemia (IRIDA) due to mutations in genes like TMPRSS6 can make oral iron therapy ineffective and chronic deficiency persistent.
- Other rare inherited disorders influence how the body handles iron at a cellular level.
These are rare but important to consider when conventional causes are ruled out and iron doesn’t respond to supplementation.
Signs It Might Be Something Hidden
If supplements and iron-rich foods don’t improve your labs or symptoms, consider these red flags:
- Persistent fatigue despite treatment
- Ferritin remaining low after months of iron therapy
- Symptoms of anemia without obvious blood loss
- A history of digestive issues, nausea, or gut discomfort
- Chronic inflammatory conditions
Tests such as complete blood count (CBC), ferritin, transferrin saturation, and inflammatory markers can help distinguish classic iron deficiency from anemia caused by inflammation or absorption issues. A gastroenterologist or hematologist may also evaluate for occult blood loss or malabsorption disorders.
The information on this website is meant to educate, not replace medical advice. Before you make any changes to your diet, lifestyle, or exercise routine based on what you read here, talk to a qualified healthcare professional who can evaluate your personal health and give you proper guidance.
