South Australia's doctors have called for major investment to improve a health "system in crisis", urging voters to carefully scrutinise promises from political parties ahead of the March state election.

With both Labor and the Liberals offering up big health spending commitments during the campaign so far, the Australian Medical Association said more money was needed to ensure the system could cope with existing and future demands.

AMA state president Michelle Atchinson said the health system was in crisis before COVID-19 but the pandemic had "crushed it", placing an enormous burden on health care workers.

"On behalf of patients, carers and family members, the AMA asks for a commitment to injecting the health system with the investment it needs," she said on Thursday.

"Funding that will overhaul the health system so it can cope with existing demands and evidence-based predictions for the future."

The AMA outlined specific areas needing extra investment including the pandemic response, ambulance ramping, hospital logjams, rural health, mental health and workforce issues.

Its calls came as the government promised an extra $123 million for upgrades to four Adelaide hospitals and Labor pledged extra funds to support people living with Motor Neurone Disease.

The government projects included $29 million for a 24-bed Geriatric Evaluation and Management unit at the Repatriation Hospital, $20 million to expand the emergency department at the Noarlunga Hospital and $22.5 million for a 16-bed dementia unit at the Modbury Hospital.

Extra beds would also be provided at the Lyell McEwin Hospital where the government said a further $5 million would be spent to expand clinical and support services, including car parking.

"Our health system has performed exceptionally well during the (COVID-19) pandemic and this additional investment will ensure we are able to continue to build a stronger future for all South Australians," Premier Steven Marshall said.

"We have embarked on a full compass hospital expansion with significant upgrades at major hospitals in the north, south, east and west of Adelaide either committed to or under way."

But the opposition said the government's announcement had been rushed out in response to Labor's recent health commitments including funds for 300 more hospital beds, 300 more nurses and 100 more doctors.

"This has all the hallmarks of a half-baked announcement rushed out by a desperate premier in a flat panic," opposition health spokesman Chris Picton said.

On Thursday, Labor announced an extra $2.4 million to support South Australians living with MND with the money to provide for specialist care and equipment.

"Labor will support people living with this disease get access to the care they need and vital equipment that can make their lives easier," Opposition Leader Peter Malinauskas said.

SA voters go to the polls on March 19.