How long does it take iodine to leave your system after a ctt scan?

Varies: Most of the contrast agent will leave your circulation in a few hours with normally functioning kidneys. It will be excreted in your urine. Iodine is a part of the contrast agent molecule.Some of this will become free iodine in the blood. Most of this is rapidly taken up by the thyroid. It can stay there for quite awhile as any other free iodine source would.