What are the possible side effects of sodium phosphate?

Seek immediate medical attention for serious side effects of sodium phosphate, including heart irregularity, seizures, problems breathing and swallowing, nausea, tiredness, rectal bleeding, changes in urination, ulcers, swelling, seizures, fainting and weight gain.

Other less serious side effects include: dizziness, headaches and stomach pain. Talk to your doctor if these become bothersome.