From the Guidelines
Intravenous (IV) iron therapy typically does not cause constipation as a common side effect. Unlike oral iron supplements, which frequently cause constipation due to direct contact with the gastrointestinal tract, IV iron bypasses the digestive system by delivering iron directly into the bloodstream 1. This route of administration avoids the gastrointestinal irritation that often leads to constipation with oral iron formulations. The most common side effects of IV iron include infusion reactions (such as headache, flushing, or dizziness), hypophosphatemia, and rarely hypersensitivity reactions.
Some key points to consider when administering IV iron include:
- IV iron is indicated if a patient cannot tolerate oral iron or if blood counts or iron stores do not improve with oral iron supplementation 1
- Several different formulations of IV iron are available that differ in dose and frequency of administration, but there is little difference in overall efficacy of iron repletion and similar risks 1
- Being truly allergic to IV iron is very rare—almost all reactions are complement activation–related pseudo-allergy, which are idiosyncratic infusion reactions that can mimic allergic reactions 1
If a patient experiences constipation during IV iron treatment, it's more likely related to other factors such as medications they may be taking concurrently, underlying conditions, dietary changes, or reduced physical activity. Patients receiving IV iron should stay well-hydrated and maintain their normal diet and activity levels. If constipation does occur during treatment, it should be evaluated to determine if other causes are responsible rather than assuming it's directly related to the IV iron therapy. According to recent expert consensus guidelines, life-threatening infusion reactions are extremely rare and concern for their occurrence should not be a barrier to the use of IV iron 1.
From the Research
IV Iron and Constipation
- The question of whether IV iron causes constipation can be addressed by examining the available evidence on the gastrointestinal side effects of iron supplements.
- According to a case report and literature review published in 2020 2, oral iron supplements can cause various side effects, including constipation.
- However, it is essential to note that the study focused on oral iron supplements, not IV iron.
- The study highlights the importance of considering the gastrointestinal pathophysiology of iron and its potential to cause bowel obstruction and constipation 2.
- There is no direct evidence provided in the available studies to confirm whether IV iron specifically causes constipation.
- Another study published in 1978 3 is not relevant to the question of IV iron and constipation, as it discusses a method for detecting toxin production in Corynebacterium diphtheriae cultures.