What happens when you take omeprazole with iron?
Dietary and supplemental iron comes in two forms: heme iron (from meat, fish, poultry) and nonheme iron (from plants, fortified foods, and most supplements). Heme iron is absorbed by its own dedicated transporter and is relatively acid-independent. Nonheme iron is where omeprazole creates trouble.
Nonheme iron is mostly in the ferric state (Fe3+) when consumed, but the enterocyte transporter DMT1 only takes up the ferrous state (Fe2+). Gastric acid plus the brush-border reductase Dcytb reduce Fe3+ to Fe2+ in the duodenum. When omeprazole suppresses acid, this reduction step is impaired and a fraction of nonheme iron passes through unabsorbed.
There is also a newer mechanism uncovered in 2019: omeprazole and other PPIs directly upregulate hepcidin (the master iron-regulatory hormone) via the aryl hydrocarbon receptor pathway, and hepcidin downregulates ferroportin, the iron exporter on the basolateral surface of enterocytes. So iron may get into the gut cell but cannot get out into circulation. This is independent of the acid effect and may explain why iron deficiency on PPIs is sometimes refractory.
Why is this important?
Iron deficiency is the most common nutritional deficiency worldwide and the most common cause of anemia. In PPI users, the risk is modestly elevated but clinically meaningful in vulnerable groups: menstruating women, pregnant women, vegetarians and vegans, frequent blood donors, patients with gastrointestinal blood loss, and older adults with marginal intake.
Symptoms develop slowly: fatigue, exercise intolerance, pale skin and conjunctivae, brittle nails, restless legs, pica (craving ice or non-food substances), shortness of breath on exertion, and in severe cases tachycardia and cognitive slowing. By the time hemoglobin drops, ferritin (the body's iron store) has been depleted for some time.
Multiple case series and observational studies link long-term PPI use with iron deficiency anemia. A 2018 nested case-control study in Gastroenterology found that 2 or more years of PPI use was associated with about 2-fold higher odds of iron deficiency. Importantly, in patients with established iron deficiency, achieving adequate repletion with oral iron is harder when a PPI is continued; some require intravenous iron.
What should you do?
- Choose the right iron form. Ferrous sulfate, ferrous fumarate, and ferrous gluconate are the standard salts. They still require some acid for optimal absorption, but they are inexpensive and effective. Iron bisglycinate (chelated iron) is less dependent on gastric acid and is often better tolerated.
- Pair with vitamin C. 250-500 mg ascorbic acid taken with iron creates a local acidic environment in the duodenum and helps keep iron in the absorbable ferrous form. This partially rescues absorption in PPI users.
- Time it. Take iron on an empty stomach when tolerated. Avoid taking it within 2 hours of the omeprazole dose, calcium supplements, dairy, tea, coffee, or whole-grain bran, all of which inhibit absorption.
- Consider every-other-day dosing. Newer evidence shows alternate-day iron dosing can improve total absorbed iron because daily dosing elevates hepcidin and suppresses absorption of the next dose.
- Check ferritin annually on long-term PPIs. Ferritin below 30 ng/mL signals depleted iron stores even before anemia appears. In menstruating women on long-term PPIs, this is worth tracking.
- IV iron if oral fails. If oral iron cannot raise ferritin despite good adherence, intravenous iron (ferric carboxymaltose, iron sucrose) bypasses the absorption issue entirely. Discuss with your doctor.
Which specific products are affected?
The interaction primarily affects nonheme iron from supplements: ferrous sulfate (Feosol, Slow Fe), ferrous gluconate (Fergon), ferrous fumarate (Ferretts), polysaccharide iron complex (Niferex), and carbonyl iron (Feosol Bifera). Heme iron polypeptide products (Proferrin) absorb via a separate pathway and are less affected, though they are more expensive.
Dietary iron is partially affected: nonheme iron from beans, lentils, spinach, fortified cereals, and tofu is absorbed less efficiently on a PPI. Heme iron from red meat, poultry, and fish is largely spared.
All PPIs have this effect: omeprazole (Prilosec), esomeprazole (Nexium), lansoprazole (Prevacid), pantoprazole (Protonix), rabeprazole (AcipHex), dexlansoprazole (Dexilant). H2 blockers (famotidine, cimetidine) have a smaller but real effect on iron absorption with chronic use.
The bottom line
Omeprazole reduces nonheme iron absorption by raising gastric pH and by upregulating hepcidin, which downregulates the iron exporter ferroportin. The risk of iron deficiency goes up with long-term use, especially in menstruating women, vegetarians, and anyone with GI blood loss. If you take a PPI and need iron, use ferrous sulfate (or iron bisglycinate for better tolerance), pair it with 250-500 mg vitamin C, separate it from omeprazole by 2 hours, and check ferritin annually. If oral iron fails to restore stores, intravenous iron is the next step. As always, do not stop the PPI on your own; work with your doctor on the lowest effective dose.