Thousands of nurses across NSW are striking for 24 hours over what they say is a "staffing crisis" in the state's hospitals.

Hundreds of nurses, many dressed in their navy blue scrubs, marched down Macquarie Street in Sydney's CBD while others joined similar rallies in the regions. 

It is the fourth time this year nurses in NSW have taken industrial action to demand mandatory nurse-to-patient ratios and better pay and working conditions.

Speaking at the rally in Sydney, NSW Nurses and Midwives Association (NSWNMA) general secretary, Shaye Candish, said nurses were worn out by staff shortages in the state's hospitals.

"This workforce is on its knees," Ms Candish said.

"We're seeing extreme versions of fatigue ... burnout and in the most extreme cases we're seeing symptoms similar to PTSD."

Michelle Rosentreter is an intensive care nurse at Sydney's Hornsby Ku-Ring-Gai Hospital and had a stark warning for the government.

"Our hospitals are not safe," she said at the rally in Sydney.

"We're not able to maintain safe staffing on a daily basis. We're working short every single day."

Of the thousands of healthcare workers in attendance, Skye Romer's case for nurse-to-patient ratios stands out.

The Prince of Wales mental health nurse said she required two spinal surgeries after being assaulted on her ward — an injury she said would have been prevented had ratios been in place.

"If we had ratios on the ward, incidents like this wouldn't happen," she said.

"We would be able to provide adequate care to our consumers. Their needs would be met and our wards wouldn't be escalating," she added.

In August, the NSW Industrial Relations Commission increased midwives and nurses' pay by 3 per cent — a 2.53 per cent wage increase and 0.5 per cent superannuation increase.

At a rally in the regional NSW city of Wagga Wagga, nurse and union branch secretary Roylene Stanley said staffing levels in the Murrumbidgee Local Health District were "dire".

"I would say every ward would have staff shortages," Ms Stanley said. 

Wagga Wagga branch delegate and nurse Natalie Ellis said she was aware of one rural hospital where a nurse worked a 20-hour shift to cover staff shortages.

"You feel physically sick walking in (to work) thinking 'I'm not going to have the tools and the ability to care for people the way I know we should be'," Ms Ellis said. 

"It's a huge commitment for people to walk off the ward which is why we haven't done it for 10 years (until this year)."

The union wants one nurse rostered on for every four patients on a shift and a one-to-three ratio in emergency departments.

The IRC ordered the union not to proceed with the strike at the request of NSW Health.

Ms Candish said it was taking a risk for today's unauthorised strike after the union was fined $25,000 earlier this year over similar action. 

The union said "life-preserving services" were being maintained in all public hospitals and health services during the 24-hour strike.

In a statement, NSW Health said measures were in place across the health system to minimise the disruptions and delays caused by the strike.

NSW Health announced a one-off payment of $3,000 in June this year for health workers, "in recognition" of their efforts during the pandemic.