If you have recently begun taking iron supplements, you may have been startled to discover that your stools have turned an alarming shade of black. This disconcerting side effect has likely left you wondering what is causing this change in bowel movements and whether it is anything to be concerned about.
We will discuss what black stool is, why iron supplements cause it, and who is most at risk. We will also provide guidance on when black stool may indicate a serious underlying problem versus when it is merely an harmless side effect of supplemental iron.
What is Black Stool?
Black stool, known medically as melena, refers to stools that have become dark black, shiny, and tarry in consistency. This dramatic change is due to the presence of partially digested blood in the stool, usually originating from bleeding that has occurred in the upper part of the gastrointestinal tract.
When taking iron supplements, black stool is caused by a different mechanism. In this case, the black coloration occurs when iron from the supplement interacts with digestive enzymes and acids, forming certain compounds that lend a black hue to the stool as it moves through the digestive system.
Why Iron Supplements Cause Black Stool
Iron supplements are commonly prescribed to help combat iron deficiency anemia. Since the body cannot absorb all of the iron provided in these high-dose supplements, some of the excess iron makes its way through the gastrointestinal tract unabsorbed.
This free unabsorbed iron then mixes with digestive enzymes and acids produced in the stomach and small intestine. The iron reacts with these compounds, resulting in a black pigmentation that colors the stool. Therefore, the more excess iron present, the darker the stool becomes.
Common Iron Supplements That Can Cause Black Stool
Some of the most commonly prescribed iron supplement formulations are more likely to cause black stools as a side effect. These include:
- Ferrous sulfate
- Ferrous gluconate
- Ferrous fumarate
- Iron polysaccharide complex
- Carbonyl iron
The high elemental iron content of these particular supplements increases the amount of unabsorbed iron that remains in the gastrointestinal tract. This excess iron reacts with digestive enzymes and acids to form the black pigmentation responsible for the discoloration.
Who Is At Risk For Black Stool From Iron?
While anyone taking iron supplements may experience black stools as a side effect, certain individuals seem to be at higher risk. These include:
- Those with sensitivity or intolerance to supplemental iron
- People taking very high doses of iron
- Individuals prone to gastrointestinal issues like nausea, constipation or diarrhea
- Those with impaired iron absorption due to digestive disorders
- People consuming iron supplements on an empty stomach or without food
Additionally, the longer someone takes iron supplements continuously, the more likely black stools will develop as excess unabsorbed iron accumulates in the gastrointestinal tract.
Signs Black Stool May Be Serious
While black stool is a common benign side effect of taking iron pills, it may potentially indicate a more serious problem in some instances. Signs that black stool may warrant medical evaluation include:
- Occurs alongside abdominal pain, especially severe pain
- Is combined with persistent diarrhea or constipation
- If you have nausea and vomiting in addition to black stool
- Presence of dark blood clots in the stool
- Stool has a very foul smell
- If you feel dizzy, fatigued, or weak along with black BM
These associated symptoms suggest potential bleeding in the upper GI tract and require prompt medical attention to identify the underlying cause.
When To See A Doctor About Black Stool From Iron
You should seek prompt medical evaluation if you experience the following more dangerous signs and symptoms along with black stool:
- Severe and persistent abdominal pain
- Stool appears tarry and has a very foul odor
- You have low blood pressure, dizziness or fainting
- Feel confused, fatigued, restless or weak overall
- You vomit blood or coffee ground looking material
These red flag symptoms may be indicative of gastrointestinal bleeding and warrant rapid medical assessment to identify and treat the cause.
Prevention Tips To Avoid Black Stool From Iron
If you want to minimize the chances of developing black stools while taking iron supplements, consider the following preventive tips:
- Take iron pills with food to reduce side effects
- Start with a low dose and gradually increase over time
- Switch to more gentle iron supplements like iron bisglycinate
- Try an iron supplement that does not contain sulfur
- Use IV iron infusions if you cannot tolerate any oral iron
Making adjustments in how you take iron can help lower the amount of unabsorbed iron moving through your digestive system, reducing the likelihood of black stools occurring.
Alternatives To Traditional Iron Supplements
Individuals who want to avoid black stools may benefit from trying iron supplements that are gentler on the digestive system. Some options include:
- Iron polysaccharide complex
- Carbonyl iron
- Heme iron supplements
- Iron amino acid chelate
- Liquid iron drops
- Nano colloidal iron
These types of iron formulations may be better tolerated, especially for those sensitive to traditional forms of supplemental iron.
Tips For Managing Black Stool From Iron
If you do develop black stools from your iron supplement, try the following tips to help manage this side effect:
- Monitor for other concerning symptoms
- Scale back your iron dosage if stools become too black
- Take a stool softener to ease passage of stools
- Increase fluid and fiber intake for bowel regularity
- Try probiotic supplements to support digestive health
While not usually serious, adjusting your dosage, hydration, diet and bowel regimen can help manage nuisance symptoms from iron-related black stools.
Finding black specks or spotting in your stool may be alarming, but it does not necessarily require stopping your iron supplement altogether. However, if your stools become extremely black and tarry, or you experience severe constipation from iron, speak with your doctor.
They can help determine if your dosage needs lowering or if you need a brief hiatus from the iron to allow the excess to clear from your system. In many cases, black stools will gradually subside over time as your body adjusts to the supplemental iron.
Never discontinue or alter prescribed iron supplements without first consulting your healthcare provider. Sudden changes in dose can negatively impact your blood iron levels.
With the proper guidance, minor adjustments can often minimize unpleasant gastrointestinal side effects, while still providing benefits against iron deficiency anemia.
While passing black and tarry stools can be disconcerting, in most individuals it is merely an inconvenient but harmless reaction to routinely taking iron pills. Using the guidance provided, you can take steps to manage this side effect and determine if any concerning symptoms need to be investigated.
Black stools generally resolve on their own. However, severe or persisting symptoms should prompt consultation with your doctor for further evaluation and management.
