Some side effects of taking iron supplements can include nausea, vomiting, constipation, diarrhea and stomach upset, according to WebMD. Iron supplements in liquid form can blacken the teeth. Taking iron supplements in high doses is unsafe and is the leading cause of poisoning death in children.
Iron supplements may worsen some conditions, such as stomach or intestinal ulcers and intestinal inflammation, explains WebMD. Furthermore, people with hemoglobin disease and diabetes should discuss iron intake with a medical provider. Pregnant or breastfeeding women who have an iron deficiency should not take more than 45 milligrams of elemental iron per day, as higher doses are likely unsafe. Although controversial, some studies show that high iron intake may be a contributing factor in heart disease.
While iron is needed for transporting oxygen and carbon dioxide, caution should be used when taking certain medications, as iron supplements can interact negatively, according to WebMD. For instance, iron may decrease the degree by which an antibiotic is absorbed by the body. This can decrease the antibiotic's effectiveness. It is recommended that people take iron two hours before or after taking an antibiotic medication. Iron supplements are commonly taken for iron deficiency anemia or to improve athletic performance.