The Americans with Disabilities Act requires employers to make accommodations for employees with disabilities unless it would create an undue hardship. Note that the ADA does not say accommodation must be considered after employees complete their introductory period.
Although employment is at will during and after the introductory period (also called orientation period, job familiarization period, or probationary period), new employees may not be eligible for employee benefits, including sick leave and medical leaves of absences, until completion of the introductory period. This period is used to assess the ability of the employee to learn and carry out job responsibilities, observe their performance, as well as attendance and “fit” for the job. It also serves as a period for the employee to assess their personal fit with the company culture, job responsibilities, and management style. Despite being a "probationary" period, the ADA applies to employees throughout the period of employment, including the introductory period.
If an employee requests leave or other accommodation during the introductory period due to a medical issue, follow the same procedures you would for a longer term employee. Use the interactive process to determine what the employee is having difficulty with in performing the job, discuss their accommodation request and whether other options are available. You may also ask for documentation to support the need for accommodation while temporarily allowing accommodation pending receipt of the medical documentation. Not every request will rise to the level of a disability. Short term illnesses that do not substantially limit a major life activity do not fall under ADA.
In evaluating whether the accommodation request would be an undue hardship for the company, you need to also consider leave or accommodations you have granted to longer term employees in similar jobs. Please see the EEOC enforcement guidelines publication at: http://www.eeoc.gov/policy/docs/accommodation.html, for a detailed discussion the Agency's undue hardship guidelines. If you find yourself in this situation also don't forget we're always here to help you think through your options.