The GI tract of a person appears to be painfully inflamed by oral iron supplements meant to battle iron deficiency anemia.

IBS & Iron Deficiency Anemia

A number of illnesses can masquerade as IBS. However, subtle overlooked iron deficiency anemia (IDA) can be a clue to discovering those conditions. This article focuses on providing an overview of iron deficiency anemia. Oral supplementation of iron may exacerbate gastrointestinal (GI) distress and IBS. Consult with your personal clinician if you feel that you may have IDA or that iron supplements may be making your existing IBS symptoms worse.

Why is iron deficiency anemia important to know about?

Iron is a critical nutrient for the bone marrow to synthesize hemoglobin. Hemoglobin binds and carries oxygen in our body. Hemoglobin covers red blood cells that travel through the bloodstream throughout the body to deliver that oxygen. Every day, we absorb iron from the intestine and lose a small amount through intestinal cells sloughing off in the stool (akin to ‘wear and tear’). The net absorption and loss results in the same amount of iron maintained in the entire body: iron homeostasis. When we lack enough dietary absorption of oral iron, have intestinal inflammation to prevent absorption, or have greater iron losses from the body, then we may have a net deficiency characterized as iron deficiency anemia (IDA).

Iron deficiency anemia symptoms

Most signs and symptoms of iron deficiency anemia are common to anemia of any underlying cause due to having low hemoglobin and blood count. These signs and symptoms include: feeling fatigued and lethargic, easily winded or short of breath especially with exertion, lightheadedness, dizziness, or passing out (syncope). If anemia is severe enough and there is underlying heart disease, some patients may experience symptoms of a heart attack such as chest pain.

One sign that is suggestive of IDA specifically is that of pica. Pica refers to the oral consumption of non-nutritive (contains no meaningful nutrition) substances such as ice, soil, clay, chalk or even sponges. Iron is necessary for the synthesis and maintenance of healthy neurons. Therefore, subtle, non-specific symptoms of IDA also may include personality changes, memory challenges or difficulty sleeping.

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Iron deficiency anemia causes

Lack of dietary intake of iron is not uncommon, especially in our Western diet where healthy foodstuffs can be increasingly expensive. Non-animal derived iron sources include: dark leafy greens, potatoes, tomatoes, lentils, soybeans, and nuts. Animal sources of iron include beef, chicken liver, and egg yolks. Pescatarian options include: tuna, mackerel, clams and oysters. Notably, a little Vitamin C is required as a co-factor for iron absorption. Vitamin C can easily be found in nearly any citrus (orange, grapefruit, kiwi, strawberries, melons) and even broccoli and peppers. Variety in your diet not only keeps your taste buds always interested but also ensures your body’s iron stores are replete.

Intestinal inflammation may be caused by the onset of celiac disease. The entire length of your 20-23 foot small intestine is a carpet of tentacles known as villi. These fingerlike projections create so much surface area to absorb nutrition including iron. Celiac patients have flattened villi from gluten absorption that reduces the surface area for absorption promoting iron deficiency.

Excess intake of aspirin or NSAID’s can cause small cuts, known as erosions or deeper ulcers in the stomach, small intestine or large intestine to slowly or quickly lose blood from the body, faster than it can be reabsorbed and recycled promoting IDA. Other inflammatory bowel diseases such as Crohn’s and Ulcerative Colitis promote iron loss with overt oozing and/or bleeding from intestinal ulcers. Also, the severe inflammatory state down-regulates hormones in the duodenum to prevent iron absorption as well. One of the most common causes of iron deficiency anemia in a female is active menstruation and in some women excess blood loss (menorrhagia).

Iron supplement pitfalls

Fortunately, iron can be supplemented and when possible, oral iron is an appropriate and convenient route. Notably, some multivitamin formulations may contain more calcium carbonate or magnesium oxide which can actually impair iron absorption. Or iron within a tablet may not release adequately to enable absorption. There is a limited amount of time to absorb oral iron from the gut. Iron is absorbed from the diet primarily in the proximal third of the small intestine known as the duodenum. As food transits past the duodenum, there is still an opportunity for iron absorption but less so as intestinal peristalsis carries the digested food forward. Surgical bypass of the duodenum also prevents physical contact of dietary iron with the duodenum to absorb iron as well. This is applicable to patients who have undergone Roux-en-Y gastric bypass for weight loss. Those patients should have a blood count and iron studies checked once or twice a year at a minimum and consider intravenous supplementation if dietary and oral iron is inadequate.

Some elements in excess can sometimes cause side effects. For instance, oral iron in some individuals can cause GI side effects by reacting with other intestinal contents via the Fenton reaction which creates an excess free radicals prompting symptoms may patients term as ‘GI distress’ and/or constipation. In my practice, if the iron deficiency anemia is deemed mild and there is no active inflammatory bowel disease (IBD, not IBS), I will work with the patient to trial oral iron. If, however, a patient demonstrates that they are intolerant to the oral iron or their hemoglobin (blood count) and iron studies do not increase after 4-6 weeks of time, then it is prudent to consider intravenous iron.

Oral vs. IV iron

Oral iron supplementation provides an inexpensive and supremely easy route of supplementation. Likewise, it does require an individual to remember to take it and to be long-term adherent for it to be effective. Indeed in mild IDA, oral iron is an ideal option to help supplement iron levels so that the bone marrow can generate more hemoglobin and correct the anemia. With short or long-term use, though, it can also cause some individuals GI distress and/or constipation.

Intravenous iron provides an individual a more controlled and accurate amount of iron over the course of several IV iron infusions. Clinicians can calculate a patient’s iron deficit via the Ganzoni equation. Depending on the type of IV iron selected, they may require anywhere from 1 – 5 intravenous infusions. The disadvantage is that it can be costly and require time off from work productivity to make infusion appointments. IV iron avoids excess oral iron exposure which prevents GI side effects. Again, patients with pre-existing underlying intestinal inflammation, specifically active Crohn’s disease and/or Ulcerative Colitis, should consider avoiding oral iron during a flare until they speak with their own IBD specialist.


Consult your physician if you are concerned about having developed one or sometimes more conditions that may predispose you to anemia. Regardless of the route of iron supplementation, blood count and iron studies should be assessed at baseline and proactively re-assessed no earlier than 4 weeks from supplementation to gauge an appropriate therapeutic effect. Oral iron supplements can exacerbate IBS symptoms with increased bloating, constipation and sometimes diarrhea.

IDA is a clue to an underlying phenomenon at play. Therefore, diagnosis and supplementation are key but actively determining the cause of IDA is equally, if not more, important.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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