Possible side effects of ferrous sulfate include stomach cramps, upset stomach, constipation and diarrhea, according to WebMD. A completely non-harmful side effect of ferrous sulfate is that can turn an individual’s stools black.
A doctor should be notified if an individual experiences severe or ongoing stomach upset, constipation or any other negative side effects due to the use of ferrous sulfate, according to MedlinePlus.
Side effects from ferrous sulfate are generally temporary and decrease as the body adjusts to the medication, according to WebMD. An individual should contact a doctor if symptoms of allergic reaction occur, such as itching, swelling, rash, dizziness or breathing difficulty.
Using ferrous sulfate may cause teeth to darken, according to MedlinePlus. Taking ferrous sulfate with water or fruit juice can minimize this effect.