How long do you keep a cast on for a sprained ankle?

Cast to boot...: Depending on the severity of a sprain, many people can avoid a cast all together with the use of a walking boot and/ or crutches. If your physician has decided you need a cast then he/ she can provide you with an estimated time frame based on how much damage they noted with the physical exam, and any imaging that may have been ordered.

Variable: If your sprain was bad enough to be in a cast and not in a boot i would leave it on for 2-3 weeks. Removal of the cast will allow range of motion but it would still need to be protected either w/ crutches a boot or ankle brace. If we can allow range of motion and protect from additional injury we can heal the ankle up faster. Re injury early on is a real possibility and needs to be protected.

Time may vary: It depends on the severity of the injury. Consult with your doctor and see how long he or she would recommend for you to have it on.