Thousands of junior doctors are expected to go on all-out strike for the first time.
The British Medical Association (BMA) is expected to announce the results of a ballot on strikes later this morning in a bitter row with the Government.
The union sent ballot papers to more than 30,000 members.
If there is a Yes vote, junior doctors will only provide emergency care for 24 hours from 8am on December 1, followed by full walkouts from 8am to 5pm on December 8 and 16.
There is expected to be mass disruption to the NHS, with hospitals forced to cancel outpatient clinics and non-urgent operations.
Health Secretary Jeremy Hunt has said the strikes - the latest stage of a fierce dispute over pay and conditions regarding a new contract for doctors in England - were "totally unwarranted" and would harm patients.
The BMA has refused to get back round the negotiating table with the Government in the row over the new contract, which is set to be imposed from next summer on doctors working up to consultant level.
Mr Hunt had tried to avert strikes with a fresh deal, including an 11% rise in basic pay and overtime pay after 7pm on Saturday evenings, a concession on the previous 10pm.
Flexible pay premiums would be applied to more specialities than just general practice and A&E care, with acute medical ward staff and psychiatrists benefiting, he said.
He argued that just 1% of doctors would lose pay because of the deal and those were limited to doctors working too many hours already.
He said maximum working hours per week would fall from 91 to 72 under the new deal.
Johann Malawana, the BMA's junior doctor committee chairman, has said the increase in basic pay was misleading as it would be "offset by changes to pay for unsocial hours - devaluing the vital work junior doctors do at evenings and weekends".
The BMA has said the Government needs to lift the threat of the contract being imposed.
It is also calling for proper recognition of unsocial hours as premium time, no disadvantage for those working unsocial hours compared with the current system, and no disadvantage for those working less than full-time and taking parental leave.