Not everyone needs iron supplements. A mineral necessary for red blood cell manufacture and oxygen transport, iron is found in all types of meat as heme iron and in plants as non-heme iron. Iron deficiency requiring supplementation occurs most frequently in women with heavy menstrual periods, pregnant women, toddlers who eat poorly and vegetarians. Non-heme iron absorbs poorly compared with heme iron. Iron supplements can irritate your stomach, causing a small amount of bleeding into the stool.
Causes
Iron, like many substances, such as aspirin, irritates the stomach lining, especially if you take it on an empty stomach. While iron absorbs best on an empty stomach, according to Healthwise, you may need to take your iron supplement with food to decrease the risk of stomach irritation that could cause bleeding. Talk to your doctor about the best way to take your iron pill if it's making you feel sick or causing bleeding in the stool.
Other Causes of Black Stools
If you're taking an iron supplement, your stools may turn black for other reasons besides blood loss in the stool. Unabsorbed iron may turn the stool dark green or black as it passes through the intestines. This has no medical significance. In fact, if your stools don't turn black, you may not be absorbing enough of the iron, especially if you take an enteric-coated pill -- a delayed-release pill -- MayoClinic.com cautions. You can increase the amount of iron you absorb from pills by eating food high in heme iron or vitamin C at the same time as your iron supplement. Gastrointestinal bleeding from other causes, such as hemorrhoids, a stomach ulcer or colon cancer could also cause blood in or on the stool.
Iron Supplement Types
Some iron supplements may cause more stomach irritation than others. Iron comes in several forms, including an injectable form that bypasses the gastrointestinal tract altogether, avoiding the issue of stomach irritation. Liquid iron absorbs more quickly than pills and may also irritate your stomach less. Enteric-coated tablets may not absorb well enough to be therapeutic, although they're easier on your stomach, the Office of Dietary Supplements explains.
Considerations
Since you take iron to prevent iron-deficiency anemia, losing blood in the stool could defeat the purpose of taking the supplements. Most people lose only small amounts of blood that may not even be visible. If you see large amounts of blood on or in the stool, see your doctor to determine if iron supplements are causing blood loss or if you have another medical problem that requires treatment.
