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Can stool appear black despite stopping iron supplements?

This Premium Q&A, reviewed and published, features a real conversation between an iCliniq user and a physician.

Patient's Query

Hello doctor,

I have had iron deficiency anemia for three months. In short, my third CBC doctor said everything is going fine, and my hemoglobin level is increasing. I have also done another blood test, even if I have not used iron supplements for two days. My blood levels were still increasing; I asked the doctor about losing my appetite and if my iron deficiency was the cause of my stomach bleeding. And he said I had to have a coffee-like stool or vomit.

Later that day, when I woke up, my lower abdomen was gurgling so much (with no pain), and I went to the toilet; that was some liquidy stool (or tarry), and I had not used iron supplement for one, and half days though it was still black (One day ago, I only took 5 mg, and the other day when I check my CBC I did not take my iron supplements at all as I forgot to take me with them)

If I had gastrointestinal bleeding, would it show up in CBC? And how long does iron supplement stay in the body?

Is it normal for my stool colors to be black even though I have not taken them for a day?

Kindly advise.

Hello,

Welcome to icliniq.com.

If you have significant gastrointestinal bleeding, it is reflected in CBC (complete blood count) in the form of decreased hemoglobin level and increased platelet count. However, the minor bleeding will not be reflected in CBC.

Iron medicine can remain in circulation for one day. So your black stool could be because of that. But still, after two more days, if your stool remains black, then investigate with stool routine micro examination and occult blood test. An occult stool blood test will detect any minor bleeding also if present. Your upset stomach could be because of an iron tablet.

I hope I have solved your query.

Thank you.

Medically reviewed byiCliniq medical review team

Published At January 19, 2023
Reviewed AtDecember 19, 2025

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