Unite encompasses the Medical Practitioners Union which represents some GPs.
The action will come a day after the Queen’s speech which is expected to include a parliamentary Bill forcing through public sector pension changes.
Unite says its members, who also include health visitors and paramedics, now face, on average, an extra £30-a-month to pay for their pensions.
Meanwhile, the BMA is set to ballot members from 15 to 29 May on two questions – whether doctors are prepared to strike, and whether they are prepared to take action short of a full strike.
Dean Royles, director of the NHS Employers organisation, said: ‘I know staff feel anxious about changes to pensions but announcements of industrial action will be distressing for patients and confusing for staff.’