Q: When is medical documentation sufficient to determine if the employee has a disability and needs an accommodation?
A: Documentation is sufficient if it substantiates that the individual has a disability and needs the reasonable accommodation requested. Sufficient medical documentation should describe the nature, severity, and duration of the impairment, the activity or activities that the impairment limits, the extent to which the impairment limits the employee's ability to perform the activity or activities, and should also substantiate why the requested reasonable accommodation is needed.
For a sample request for medical information, see JAN's A to Z: Medical Exams and Inquiries. Employers should customize this form on a case-by-case basis depending on the information that is needed.
For EEOC's guidance on medical documentation in response to an accommodation request, see question 6 in Reasonable Accommodation and Undue Hardship under the ADA.
Source: https://askjan.org/articles/Requests-For-Medical-Documentation-and-the-ADA.cfm