“What are the side effects of a CT scan with contrast dye?”

No significant side effects with normal kidney function. You will have to drink a lot of water after the CT scan.

Immediately after injection, one might feel flushing and warmth. In a patient with normal renal function, that should be it unless there is a contrast allergy. (Iodine). In patients with diminished renal function, function may worsen. In a normal person - no after-effects from contrast.