More than 30 unions and campaigning organisations, including the BMA, will be taking part and voicing opposition to public sector cuts following the election - whichever party wins.
BMA's chairman Dr Hamish Meldrum will also be speaking at the event against market reforms of healthcare.
Dr David Wrigley, a member of BMA's council and GPC, said: ‘This is a great opportunity for doctors and medical students to show their commitment to the NHS and other public services. We've seen first-hand the damaging effects of market reforms in primary care.
‘It is vital we ensure the NHS is the best it can be for our patients and that taxpayers' money is used on frontline NHS services and not siphoned off to big businesses in the City.'
The event starts at noon at Temple Place on the Embankment in London. A march will set off at 1pm to Trafalgar Square.