Common side effects of ferrous sulfate include upset stomach, anorexia, diarrhea, cramping, vomiting and dark or green stools, according to drugs.com. These gastrointestinal side effects occur in roughly 25 percent of patients taking 325-mg doses three times daily, states drugs.com.
Overdose symptoms include nausea, severe stomach pain, bloody diarrhea, coughing up blood or vomit that looks like coffee grounds, shallow breathing, weak and rapid pulse, blue lips, pale skin and seizure.
In those allergic to ferrous sulfate, reactions include tightness of the chest, breathing problems, itching and hives; swelling of the face, tongue, lips or mouth may also occur, according to drugs.com. Since some drugs interact with ferrous sulfate, it is important to notify a doctor or pharmacist of any current supplements and over-the-counter or prescription medications prior to use.
Patients are advised to take the mineral on an empty stomach -at least one hour before or two hours after meals- and avoid taking antibiotics and antacids within two hours before and after taking ferrous sulfate, warns drugs.com.
Those that often consume alcohol or receive regular blood transfusions and those with iron overload syndrome, hemolytic anemia, porphyria or thalassemia are advised to ask their doctor or pharmacist if it is safe to take ferrous sulfate.