Some 75,000 public health professionals in the Madrid region were called to join the protest to mark the last day of a two-day strike against deep spending cuts by the crisis-hobbled national government and plans by the regional government to privatise hospitals and health centres.
"The people should not have to pay for private health care," said paediatrician Veronica Sanchez of Severo Ochoa hospital, amid a swarm of demonstrators who defied the cold to march through the capital wielding placards with messages such as "We're selling our health" and "Health should be defended, not sold".
Geriatrics specialist Fatima Branas of soon-to-be-privatised Infanta Leonor hospital said it was rare for health professionals to stage a mass protest. But she said the privatisation plans were the last straw.
"We've undergone cuts before and that hasn't made us take to the streets," she said, calling to "put the breaks" on the Madrid regional government's plans to privatise six hospitals and 27 health centres of the 270 in the region.
Madrid public health professionals plan to strike again on December 4 and 5. Specialists have been called to stage an indefinite strike.
At the national level, Prime Minister Mariano Rajoy's government has slashed health spending by seven billion euros ($9.1 billion) a year as part of a campaign to squeeze 102 billion euros out of the crisis-racked country's budget by 2014.