Can you get a cortisone shot on a cyst twice?

You did not specify whether you are talking about an acne or rosacea cyst or an inflamed epidermoid (sebaceous) cyst. Acne or rosaceal acne cysts may respond to one injection session, so long as the correct concentration and amount were injected. However, it is not uncommon to require a second or even a third treatment session to achieve optimal improvement. Since steroids depot in the area of the injection for between 21-28 days, it is most prudent to schedule a second session not sooner than three weeks or preferably four afterward to avoid steroid atrophy at the site. If you have an inflamed epidermoid cyst, the entrapped contents may need to extruded physically before injection. It is wise to be sure that you are consulting with a board certified aesthetic dermatologist. Best of luck.