Based solely on the information you posted, no. If your medical condition qualifies as a disability under the ADA, then your employer will have to enter into an interactive process with you to determine whether any "reasonable accomodation" of your disability is feasible that would still allow you to perform the essential functions of your job. ANY reasonable accommodation will comply with the law, even if it's not the accommodation you requested.
Whether your medical condition qualfies as a disability and if so, what constitutes a reasonable accommodation, and lastly, whether working the mandations is an essential function of your job is unknown. Also keep in mind that your employer does not have to force other employees to work the extra shifts in order to accommodate you. If you have a disability as defined in the ADA that prevents you from working double shifts, then asking other employees if anyone would like to volunteer for the extra hours would be a reasonable accommodation.