In general, it takes 24/48hrs for the contrast to be completely eliminated from the body when the kidneys are functioning well. For people with kidney problems, it takes longer than usual for it to be eliminated. So it is essential to be well hydrated before and after receiving the contrast to help flush the contrast from the body and reduce the risk of acute kidney injury.

48 hours or so

The dye used for CT scans is known as contrast dye. This iodine-based contrast agent is filtered through the kidneys and excreted through urine. Those with normal kidney function usually eliminate it within 24-48 hours. For those with kidney disease or reduced kidney function, it could take longer.