First, if you need a reasonable accommodation because of a disability, you must first ask your employer for it – the initial burden is upon you to do so, and because the employer is not allowed to ask you if you are disabled. Once you have asked, the employer may then ask for more information to help provide a reasonable accommodation – you must provide this information, including any medical documentation relevant – in order to receive any such reasonable accommodation. However, your employer does not have to provide an accommodation that is not reasonable, i.e. to expensive to implement or would cause an “undue hardship” to the employer. An employer may also provide a modified work schedule to accommodate a disabled person’s work needs.
If you are denied reasonable accommodations, you should file a claim with the Equal Employment Opportunity Act or file a complaint under the ADA.