An investigation has found young doctors routinely clock up more than 87 hours per week, even though the UK has adopted rules that state staff should work no more than an average of 48 hours unless they choose to do so.
But rotas imposed by many health boards mean doctors are clocking on for an entire week of back-to-back shifts of at least 12 hours.
Ayrshire and Arran, Fife, Forth Valley and Grampian and Lothian roster some doctors to work 87 hours or more a week. In Ayrshire, the maximum working week is 91 hours - seven consecutive day shifts of 13 hours.
The British Medical Association (BMA), which represents doctors north of the Border, said although the shift patterns did not breach the European Working Time Directive, they went against its spirit.
Dr David Reid, chairman of the BMA's Scottish Junior Doctors Committee, said: "If you were a patient you would not necessarily want to be treated by someone who has been rotared for 90 hours, who is coming to the end of a seven-day run of long shifts."
Ayrshire and Arran said it was reviewing rotas to ensure training, well-being and patient safety were not compromised.
Meanwhile, the Scottish Government said it will not freeze pay rises for NHS staff, following moves to halt increases south of the Border.
Westminster proposals to cancel a 1% rise were an attack on staff and a "betrayal" of the NHS, Health Secretary Alex Neil said.
The UK Department of Health argue the increase is not affordable given the current NHS system of automatic incremental salary rises.