• In no case should medical students be scheduled to be on duty more than 80 hours in any week. On typical clinical rotations, medical students should not be scheduled to be on duty for more than 24 hours consecutively; continuous duty in high intensity settings (e.g., emergency rooms, critical care units) should, in general, be scheduled for no more than 12 hours. These guidelines must be applied with sufficient flexibility, to ensure that thorough exchange of information and proper transfer of patient care responsibilities occurs whenever medical students who are going off duty sign over the care of patients to other medical students or to teaching physicians.
• Duty-free   intervals between periods on call should be at least 8 hours long.
• Medical students should not be required to have overnight, on-call duty more frequently than one night in three, as averaged over 4 weeks.
• Medical students should have at least 24 consecutive hours free of all assigned duty every seven days. 
• The on-duty time medical students spend delivering patient care services of marginal or no educational value should be minimized. 

Limiting required duty hours does not imply that medical students must cease providing essential patient care services at arbitrary cut-off times. Priority must always be given to patient safety and well-being and to avoiding transferring patient care responsibilities to others at inappropriate times in the continuum of care (e.g., during an operative procedure, in the midst of a rapidly evolving clinical event). A tired medical student who is intimately familiar with a sick patient is often better able to provide quality care than is a fully rested medical student who is unfamiliar with the details of the case.

Taken from:AAMC Policy Guidance on Graduate Medical Education- Assuring Quality Patient Care and Quality Education and adapted for medical students.