I have had flu like symptoms after iron infusions also, both times they started 2-3 days after the infusion and lasted a few days. Very tired, achy, chills, one time I had a headache. My infusions were 4 months apart, 1.5 grams of iron in each. Just curious, are you getting Venofer or Monoferric? How much are they trying to give you at once?