Medical questions a potential employer can ask during the pre-offer phase are particularly limited. Once the company has extended you an offer, however, the questions are allowed to become more in-depth and personal.
Americans With Disabilities Act
The Americans with Disabilities Act provides guidelines for employers to follow regarding questions about personal disability and medical examinations. The only time when questions about disability are allowed is after a job offer is given and accepted.
During the pre-offer stage, an employer is legally allowed to ask about your physical requirements related solely to the job you are applying for and your ability to perform and carry out the job you are interviewing for. These rules ensure that an individual's employment future with this employer is not tainted due to prior realisation of a disability.
During the post-offer stage, your employer can request a medical examination as well as ask questions regarding any disabilities you may have. If the job offer is rescinded after an examination or your answer to a disability-related question, the government will look into the true reason for your dismissal.
During employment, you can be asked any disability question regarding your job position and may be tested for drug or alcohol use at any time depending on your employer's policy.
What an Employer Cannot Ask
You cannot be asked about a current or past physical or mental illness, any current or past addictions to controlled substances or personal information about receiving workers' compensation from a previous employer.