Written by Aisha Saleem, Pharmacist & Health Writer at PharmaHealths.com
Last Updated: August 20, 2026
Iron deficiency anemia rarely comes from one single problem. It usually comes down to three mechanisms: you’re not taking in enough iron, you’re losing more blood than your body can replace, or your gut isn’t absorbing the iron you do consume.
Patients often expect me to point to their diet as the culprit, and sometimes it is. But in my experience, it’s more often something less obvious, a slow, ongoing blood loss that nobody has connected to fatigue yet, or a medication sitting quietly in their cabinet that’s been working against their iron levels for months.
Key Statistics on the Causes of Iron Deficiency Anemia
Iron deficiency anemia affects an estimated 30-50% of the world’s population at some point, according to a review published by the Korean Society of Pediatric Hematology Oncology, making it far more common than most people realize until they’re tested for it. Menstrual blood loss stands out as the single most important cause of iron deficiency in women who haven’t yet reached menopause, per a review in the peer-reviewed journal Pharmaceuticals.
Medications play a bigger role in this than most people expect. NSAID use, including over the counter options like ibuprofen and aspirin, is suspected to be the underlying cause in roughly 10 to 15% of all iron deficiency anemia cases, according to a clinical review from ScienceInsights. What makes this harder to catch is that more than half of NSAID users who develop anemia this way shows no visible signs of bleeding at all, and over 60% have no identifiable ulcer on endoscopy, meaning the blood loss is diffuse rather than coming from one obvious source. Long term anticoagulant use roughly doubles the odds of developing iron deficiency anemia compared to not using one, per the same review, and the risk climbs further when an anticoagulant, an NSAID, and a PPI are combined, since each interferes with iron status through a different mechanism.
Blood Loss (The Most Common Cause in Adults)
Blood loss is the leading cause of iron deficiency anemia in adults, and it doesn’t always look dramatic. Heavy menstrual periods are the most frequent source in women who haven’t reached menopause, and the loss can be significant enough to outpace what a normal diet replaces month after month.
Gastrointestinal bleeding is the other major contributor, and it’s often silent. Ulcers, colon polyps, colorectal cancer, and inflammatory conditions of the gut can all cause slow, ongoing blood loss that never shows up as visible blood in the stool. This is exactly why unexplained iron deficiency anemia in a man, or in a woman past menopause, always warrants a proper GI workup rather than just starting iron tablets and moving on.
Can Medications Cause Iron Deficiency Anemia?
Yes, and this is a cause I find gets far too little attention outside a pharmacy consultation.
NSAIDs, including ibuprofen, naproxen, and regular aspirin, are a well-documented cause of iron deficiency through occult gastrointestinal bleeding, with NSAID use suspected to underlie 10 to 15% of all iron deficiency anemia cases, according to the same ScienceInsights clinical review. The mechanism involves small, often painless erosions across the stomach and intestinal lining that bleed steadily without triggering any obvious warning symptoms. Anyone on daily NSAID therapy for arthritis or chronic pain should have their iron status checked periodically, even without stomach symptoms.
Proton pump inhibitors, the acid reducing medications prescribed for reflux and ulcers, work through an entirely different route. By suppressing stomach acid, they reduce the acidic environment your gut needs to convert dietary iron into a form it can absorb, an effect documented in case reports of patients developing iron deficiency anemia after years of continuous PPI use, and confirmed in a 2024 study in Digestive Diseases that found a significant association between PPI use and iron deficiency anemia in patients with celiac disease specifically. Anticoagulants add a third mechanism on top of these two, since they make any existing source of bleeding, however minor, harder for the body to control on its own.
If you’re on any of these medications long-term, this is worth raising with your prescriber rather than adjusting anything yourself. I go into supplement dosing and how to manage this alongside medication use in my article on [iron supplement dosage].
Malabsorption (When Your Gut Can’t Take in Iron)
Even with a good diet and no bleeding, some people can’t absorb iron properly, and this is where conditions affecting the gut lining come in.
Celiac disease damages the small intestine lining where most iron absorption happens, and untreated celiac disease is a common, often overlooked cause of unexplained iron deficiency anemia. Inflammatory bowel disease, including Crohn’s disease and ulcerative colitis, creates a double burden of poor absorption alongside ongoing blood loss from an inflamed gut lining. Gastric bypass and other weight loss surgeries carry a similar risk, since these procedures bypass the section of the small intestine where iron absorption is concentrated, and H. pylori infection has also been linked to reduced iron absorption independent of any bleeding it might cause.
Poor Dietary Intake
A diet low in iron rich foods rarely causes iron deficiency anemia on its own in someone who’s otherwise healthy, but it becomes a real risk factor once combined with increased demand or ongoing losses.
Vegetarians and vegans face a higher risk here, not because plant foods lack iron entirely, but because non heme iron from plant sources absorbs far less efficiently than the heme iron found in meat, fish, and poultry. Toddlers and young children are another group worth flagging specifically. Picky eating combined with excessive cow’s milk intake, which is low in iron and can interfere with absorption of what little iron is consumed, is a common and under-recognized cause of iron deficiency in early childhood. I cover food sources and absorption strategies in more depth in my article on [an iron rich diet for anemia].
Increased Iron Demand (Pregnancy, Growth, and Endurance Training)
Some causes of iron deficiency anemia come down to the body simply needing more iron than usual, rather than losing it or failing to absorb it.
Pregnancy roughly doubles iron requirements to support the growing fetus and the expanding blood volume that comes with it, which is why iron deficiency anemia is so common in pregnancy even among people who ate well beforehand. Rapid growth spurts in children and adolescents create a similar, if smaller, spike in demand. Endurance athletes are a less obvious group in this category. Sustained training can increase iron loss through the gastrointestinal tract and through the mechanical breakdown of red blood cells that happens with repetitive high impact activity, a pattern documented by the National Heart, Lung, and Blood Institute among competitive runners and other endurance sport participants.
Chronic Disease and Inflammation
Long term inflammatory and chronic conditions cause iron deficiency through a mechanism that’s different from simple blood loss or poor intake.
Congestive heart failure, chronic kidney disease, and inflammatory bowel disease are all associated with what’s called functional iron deficiency, where the body’s iron stores aren’t necessarily empty but inflammation prevents that iron from being properly mobilized and used, according to a review in the peer-reviewed journal PMC. People on dialysis face an added layer of risk, particularly when they’re also taking medications that stimulate red blood cell production, since these drugs increase the body’s iron demand faster than it can typically be replaced through diet or oral supplements alone.
Conclusion
Iron deficiency anemia almost always traces back to blood loss, poor absorption, increased demand, or a combination of these, and medications you might not think to mention to your doctor can play a bigger role than expected. Identifying the actual cause, rather than just starting iron supplements, is what makes treatment stick.
Disclaimer
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any treatment for iron deficiency anemia, and never stop a prescribed medication without medical guidance.
References
• Na Hee Lee, Iron Deficiency Anemia — Korean Society of Pediatric Hematology-Oncology — https://oalib-perpustakaan.upi.edu/Record/doaj_20c83d7432b144188d103e0f8c76d205
• Pharmaceuticals (MDPI), Iron Deficiency and Iron Deficiency Anemia: A Comprehensive Overview of Established and Emerging Concepts — https://www.mdpi.com/1424-8247/18/8/1104
• Science Insights, What Drugs Can Cause Iron Deficiency Anemia? — https://scienceinsights.org/what-drugs-can-cause-iron-deficiency-anemia/
• Imai et al., Iron Deficiency Anemia Due to the Long-term Use of a Proton Pump Inhibitor, Internal Medicine (PMC) — https://pmc.ncbi.nlm.nih.gov/articles/PMC5891535/
• Digestive Diseases, Proton Pump Inhibitor Use and Iron Deficiency Anemia in Celiac Patients — https://pure.psu.edu/en/publications/proton-pump-inhibitor-use-and-iron-deficiency-anemia-in-celiac-pa/
• PMC, Iron Deficiency and Iron Deficiency Anemia in Chronic Disease — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12249883/
• National Heart, Lung, and Blood Institute (NHLBI), Iron-Deficiency Anemia — https://www.nhlbi.nih.gov/health/anemia/iron-deficiency anemia
