Reasons Why Patients Don’t Respond To Iron

Iron therapy can be life-changing for some anemia patients and help them improve their energy and ultimately, their quality of life. Sometimes anemia isn’t responsive to iron. In this article, I discuss my top reasons why patients don’t respond to iron therapy.


When I consider reasons why patients don’t respond to iron, I always start with adherence. Iron can be upsetting to the stomach and may cause some bothersome constipation as well. In addition to adverse effects, it takes a little time for patients to respond to iron replacement. Because of these factors, adherence is the first place to start when addressing non-response to iron therapy.

Poor Absorption

Oral iron supplements may be difficult for some patients to absorb thus leading to insufficient replacement and a non-response. You should be aware of certain foods and beverages that may impact iron absorption. Ideally, it is recommended to give iron by itself (without food or non-water beverages).

In the beverage category, coffee and tea can both impair the absorption of iron. Calcium supplements and calcium-containing food can also reduce the absorption of iron.

Drug Interactions

The pH of the stomach directly impacts the absorption of iron. Because of this fact, any medication that raises the pH of the stomach can ultimately lower the absorption of iron. Any medication considered to have antacid activity will reduce the absorption of iron. Such medications include PPIs, H2 blockers, and OTC quick relief antacids such as Tums or Rolaids. This always makes for a great board exam question!

Anemia of Chronic Disease

From a medical standpoint, clinicians must ensure that the diagnosis is correct. If adherence is deemed not to be an issue, a reassessment of the diagnosis should take place. In anemia of chronic disease, iron replacement therapy will likely have no effect on improving the hemoglobin value. The only thing that can be done in this situation is to weigh the risk versus benefit of using erythropoietin agents to raise the hemoglobin.

Those are my top 4 reasons why patients don’t respond to iron. What else would you add to this list?

Eric Christianson, PharmD, BCPS, BCGP

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  1. Nancy

    Eric, for anaemia of chronic disease, wouldn’t parenteral iron be of value as the iron absorption is inhabited by elevated hepcidin level??

  2. Brooke Hofmeyer

    Low vitamin C diet. I always took mine with a kiwi. Peppers or broccoli may be good lower suger options.


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Written By Eric Christianson

November 8, 2023

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