Iohexol is an iodine-based liquid called a contrast agent. It is used for computed tomography (CT) and X-ray imaging scans to reveal details of the body's interior structures, such as blood vessels and organs, which would not show during a scan without contrast. Sold under the brand Omnipaque, iohexol is administered by injection or by mouth prior to a scan. Although this contrast agent is often called a "radiopaque dye", it does not actually dye any internal tissue a different color. It is opaque to X-rays which makes the tissue where it is located appear white on the image. This allows the doctor to see details in the image that would not otherwise be visible. Iohexol is excreted from the body in urine.