Why Iron Pills Hurt Your Stomach and What to Do About it

Jan 5, 2026 | 3 min read
Why Iron Pills Hurt Your Stomach and What to Do About it

If you’ve ever taken an iron pill and felt queasy, bloated, constipated or like your stomach’s on fire, you’re not alone. Many people starting iron supplements notice uncomfortable digestive side effects — and there are good reasons for that. So let’s get into it!


Iron Pills have High Levels of Iron

As per Health Canada, most individuals, depending on their biology and life stage, can require anywhere from 7mg to 27mg of iron per day. However, iron supplements can range from providing 60mg to 120mg of iron per dose. This is because iron supplements need to have higher levels of iron since iron is very poorly absorbed in the gut. But, the catch is that all this extra iron tends to sit around in your stomach, causing uncomfortable side effects. 

 

The Ingredients in Iron Pills can Irritate Your Gut

Oftentimes, iron pills contain ferrous iron salts. When these salts dissolve in your stomach it causes chemical reactions that release molecules that can irritate your stomach and intestinal lining causing pain, nausea, and, in rare cases, mucosal injury (so-called “iron-pill gastritis”) (American Journal of Physiology-Gastrointestinal and Liver Physiology).


Iron Pills can Change Your Microbiome

Some studies suggest that all the extra iron in iron pills can alter your gut bacteria (Bloor, 2021). This means iron pills can potentially reduce the amount of healthy bacteria and allow potentially harmful bacteria to grow, leading to inflammation, cramps, and changes in stools (Loveikyte, 2023). For this reason in combination with those mentioned above, people using iron supplements often experience slow intestinal transit, producing constipation and hard, dark stools and sometimes diarrhea (Bloor, 2021). 


What You Can Do About It?

While some people may require iron pills, or a combination of treatments, some have turned to the Lucky Iron Fish/Leaf for a side-effect free solution. Unlike iron pills, the Lucky Iron Fish/Leaf adds 6-8mg of easy to absorb iron to any liquid meal. In fact, regular use of the Lucky Iron Fish/Leaf has shown to be just as effective at improving iron levels as iron supplements (Armstrong, 2017). However, since every person’s iron needs are different, it is recommended to consult your healthcare team prior to making any changes to your routine.

 

Sources:

Health Canada

New method to study oxidative damage and antioxidants in the human small bowel: effects of iron application

Oral Iron Supplementation - Gastrointestinal Side Effects and the Impact on the Gut Microbiota

The effect of iron therapy on oxidative stress and intestinal microbiota in inflammatory bowel diseases

The Lucky Iron Fish: a simple solution for iron deficiency

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