Tens of thousands of healthcare workers in the United States walked off the job Wednesday, beginning one of the sector's largest strikes in recent history, as America's year of labor discontent rolled on.

The walkout of more than 75,000 workers at Kaiser Permanente, the country's largest non-profit healthcare organization, comes as surging inflation has spurred industrial action across the US, from Hollywood actors to Detroit auto workers.

People on the picket lines in Los Angeles on Wednesday said they were underpaid and overworked.

"Ever since the pandemic hit, we lost a lot of members and we never recovered them," X-ray technician Armando Velasco told AFP.

"And now we're at the brink, we're at the precipice."

Nurse Kathy Lozoya said the rocketing cost of living in southern California was making life very difficult.

"Kaiser Permanente has reported billions of dollars in profits, so all we're asking from Kaiser CEOs is to share those profits with the frontline workers," she said.

"All we're asking is a fair contract so that we can be able to live."

Fellow nurse Scarleth Rocha said she feared a staff shortage was not good for patients.

"Working 12-hour shifts, working with 26 patients per one nurse is not ideal, and it's not safe for nurses to work with that many patients in one place," she said.

Kaiser Permanente locations in California, Colorado, Oregon, and Washington state were expected to be affected by the three-day strike. A small number of workers in Washington, DC, and Virginia were set to walk out for 24 hours.

Kaiser said centers would remain open, but warned there would be "longer-than-usual" wait times.

A Kaiser spokesman told journalists on Tuesday that talks were continuing.