My employer ask me if I needed to take any daily medication, just so they could set apart my regular break from my medication break. But that didn't affect me.
Are employers allowed to ask anything about medications or side effects if they do not impair your ability to do your job? I do NOT mean any kind of narcotics. That was all I could find was info on narcotics.
If it's something that will not impair your ability .. I believe there is no reason for them to ask about them. If you are taking a prescription antibiotic for example will not have a side affect that will hamper your ability .. But .. if it's something, even a simple over the counter medications that CAN impair you .. Like cough medicines, even allergy medications .. That can make you drowsy, and will warn against operating machinery .. So, in that case, I would think your employer would have an obligation to make sure you don't only danger yourself but others around you on the job site.