Yes you do, unless there is some legitimate medical reason for your inability to attend, in which case you may be able to delay your appointment. OWCP has every right to scheduled medical exams for you at “reasonable” intervals.
Our lives can include set backs, recoveries from disabilities, or becoming permanently or severely disabled. Life continues regardless of any change, injury or disability.
If you are in dispute with a federal agency get help and let your help carry the burden while you get on with your life.
If you are injured or disabled, get treatment, and get on with your life. If you are in treatment, follow your doctor’s orders while you get on with your life.
If your supervisor needs you at work and you cannot be there, take a moment to sympathize with how your absence affects your co-workers, and then move forword with your healing and with your life.
Remember to trust your physicians and representatives (or replace them with ones you can trust), seek refuge and comfort in your friends and family, do the things you need to do, and be with the people you care about. Life does go on.