Get emergency medical help if you have signs of an allergic reaction to ferrous sulfate: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
severe stomach pain or vomiting;
cough with bloody mucus or vomit that looks like coffee grounds;
fever; or
bloody or tarry stools.
Common ferrous sulfate side effects may include:
diarrhea, constipation;
nausea, stomach pain;
green-colored stools; or
loss of appetite.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Ferrous sulfate side effects (more detail)
